Name

The Mongol Empire is also referred to as the "Mongolian Empire" or the "Mongol World Empire" in some English sources.

The empire referred to itself as (, 'nation of the great Mongols' or the 'great Mongol nation') in Mongol or ( the 'whole great nation') in Turkic.

After the 1260 to 1264 succession war between Kublai Khan and his brother Ariq Böke, Kublai's power became limited to the eastern part of the empire, centered on China. Kublai officially issued an imperial edict on 18 December 1271 to give the empire the Han-style dynastic name of "Great Yuan" (Dai Yuan, or Dai Ön Ulus; 大元 Dà Yuán) and to establish the Yuan dynasty. Some sources give the full Mongol name as Dai Ön Yehe Monggul Ulus.

Background

Twelfth-century Mongolia

The area around Mongolia, Manchuria, and parts of North China had been controlled by the Khitan-led Liao dynasty since the 10th century. In 1125, the Jin dynasty founded by the Jurchens overthrew the Liao dynasty and attempted to gain control over former Liao territory in Mongolia. In the 1130s the Jin dynasty rulers, known as the Golden Kings, successfully resisted the Khamag Mongol confederation, ruled at the time by Khabul Khan, great-grandfather of Genghis Khan.

The Mongolian Plateau was occupied mainly by five powerful tribal confederations (khanlig): Keraites, Khamag Mongol, Naiman, Mergid, and Tatar. The Jin emperors, following a policy of divide and rule, encouraged disputes among the tribes, especially between the Tatars and the Mongols, in order to keep the nomadic tribes distracted by their own battles and thereby away from the Jin. Khabul's successor was Ambaghai Khan, who was betrayed by the Tatars, handed over to the Jurchen, and executed. The Mongols retaliated by raiding the frontier, resulting in a failed Jurchen counter-attack in 1143.

In 1147, the Jin somewhat changed their policy, signing a peace treaty with the Mongols and withdrawing from a score of forts. The Mongols then resumed attacks on the Tatars to avenge the death of their late khan, opening a long period of active hostilities. The Jin and Tatar armies defeated the Mongols in 1161.

During the rise of the Mongol Empire in the 13th century, the usually cold, parched steppes of Central Asia enjoyed their mildest, wettest conditions in more than a millennium. It is thought that this resulted in a rapid increase in the number of war horses and other livestock, which significantly enhanced Mongol military strength.

Rise of Genghis Khan

Known during his childhood as Temüjin, Genghis Khan was a son of a Mongol chieftain and rose very rapidly as a young man by working with Toghrul Khan of the Kerait. After Temujin went to war against Kurtait (also known as Wang Khan; given the Chinese title "Wang" for its meaning of King), who was the most powerful Mongol leader at the time, he gave himself the name Genghis Khan. He then enlarged his Mongol state under himself and his kin, with the term Mongol coming to be used in reference to all Mongolic speaking tribes under the control of Genghis Khan. His most powerful allies were his father's friend, Khereid chieftain Toghrul, and Temujin's childhood anda (i.e. blood brother) Jamukha of the Jadran clan. With their help, Temujin defeated the Merkit tribe, rescued his wife Börte, and went on to defeat the Naimans and the Tatars.

Temujin forbade the looting of his enemies without permission, and he implemented a policy of sharing spoils with his warriors and their families instead of giving them all to the aristocrats. These policies brought him into conflict with his uncles, who were also legitimate heirs to the throne; they regarded Temujin not as a leader but as an insolent usurper. This dissatisfaction spread to his generals and other associates, and some Mongols who had previously been allies broke their allegiance. War ensued, and Temujin and the forces still loyal to him prevailed, defeating the remaining rival tribes between 1203 and 1205 and bringing them under his sway. In 1206, Temujin was crowned as the khagan (Emperor) of the Yekhe Mongol Ulus (Great Mongol State) at a Kurultai (general assembly/council). It was there that he assumed the title of Genghis Khan (universal leader) instead of one of the old tribal titles such as Gur Khan or Tayang Khan, marking the start of the Mongol Empire.

History

Early organization

Genghis Khan introduced many innovative ways of organizing his army: for example dividing it into decimal subsections of arbans (10 soldiers), zuuns (100), Mingghans (1000), and tumens (10,000). The Kheshig, the imperial guard, was founded and divided into day (khorchin torghuds) and night (khevtuul) guards. Genghis rewarded those who had been loyal to him and placed them in high positions, as heads of army units and households, even though many of them came from very low-ranking clans.

Compared to the units he gave to his loyal companions, those assigned to his own family members were relatively few. He proclaimed a new code of law of the empire, Ikh Zasag or Yassa; later he expanded it to cover much of the everyday life and political affairs of the nomads. He forbade the selling of women, theft, fighting among the Mongols, and the hunting of animals during the breeding season.

He appointed his stepbrother Shikhikhutug as supreme judge (jarughachi), ordering him to keep records of the empire. In addition to laws regarding family, food, and the army, Genghis also decreed religious freedom and supported domestic and international trade. He exempted the poor and the clergy from taxation. He also encouraged literacy and the adaptation of the Uyghur script into what would become the Mongolian script of the empire, ordering the Uyghur Tata-tonga, who had previously served the khan of Naimans, to instruct his sons.

Push into Central Asia

Genghis quickly came into conflict with the Jin dynasty of the Jurchens and the Western Xia of the Tanguts in northern China. He also had to deal with two other powers, Tibet and Qara Khitai.

Before his death, Genghis Khan divided his empire among his sons and immediate family, making the Empire the joint property of the entire imperial family who, along with the Mongol aristocracy, constituted the ruling class.

Genghis Khan arranged for the Chinese Taoist master Qiu Chuji to visit him in Afghanistan, and also gave his subjects the right to religious freedom, despite his own shamanistic beliefs.

Death of Genghis Khan and expansion under Ögedei (1227–1241)

Genghis Khan died on 18 August 1227, by which time the Mongol Empire ruled from the Pacific Ocean to the Caspian Sea, an empire twice the size of the Roman Empire or the Muslim Caliphate at their height. Genghis named his third son, the charismatic Ögedei, as his heir. According to Mongol tradition, Genghis Khan was buried in a secret ___location. The regency was originally held by Ögedei's younger brother Tolui until Ögedei's formal election at the kurultai in 1229.

Among his first actions Ögedei sent troops to subjugate the Bashkirs, Bulgars, and other nations in the Kipchak-controlled steppes. In the east, Ögedei's armies re-established Mongol authority in Manchuria, crushing the Eastern Xia regime and the Water Tatars. In 1230, the great Khan personally led his army in the campaign against the Jin dynasty of China. Ögedei's general Subutai captured the capital of Emperor Wanyan Shouxu in the Siege of Kaifeng in 1232. The Jin dynasty collapsed in 1234 when the Mongols captured Caizhou, the town to which Wanyan Shouxu had fled. In 1234, three armies commanded by Ögedei's sons Kochu and Koten and the Tangut general Chagan invaded southern China. With the assistance of the Song dynasty the Mongols finished off the Jin in 1234.

Many Han Chinese and Khitan defected to the Mongols to fight against the Jin. Two Han Chinese leaders, Shi Tianze, Liu Heima (劉黑馬, Liu Ni), and the Khitan Xiao Zhala defected and commanded the 3 Tumens in the Mongol army. Liu Heima and Shi Tianze served Ogödei Khan. Liu Heima and Shi Tianxiang led armies against Western Xia for the Mongols. There were four Han Tumens and three Khitan Tumens, with each Tumen consisting of 10,000 troops. The Yuan dynasty created a Han army 漢軍 from Jin defectors, and another of ex-Song troops called the Newly Submitted Army 新附軍.

In the West, Ögedei's general Chormaqan destroyed Jalal al-Din Mangburni, the last shah of the Khwarizmian Empire. The small kingdoms in southern Persia voluntarily accepted Mongol supremacy. In East Asia, there were a number of Mongol campaigns into Goryeo Korea, but Ögedei's attempt to annex the Korean Peninsula met with little success. Gojong, the king of Goryeo, surrendered but later revolted and massacred Mongol darughachis (overseers); he then moved his imperial court from Gaeseong to Ganghwa Island.

In 1235, the Mongols established Karakorum as their capital lasting until 1260. During that period, Ogedei Khan ordered the construction of a palace within the surrounding of its walls.

Invasions of Kievan Rus and central China

Meanwhile, in an offensive action against the Song dynasty, Mongol armies captured Siyang-yang, the Yangtze and Sichuan, but did not secure their control over the conquered areas. The Song generals were able to recapture Siyang-yang from the Mongols in 1239. After the sudden death of Ögedei's son Kochu in Chinese territory the Mongols withdrew from southern China, although Kochu's brother Prince Koten invaded Tibet immediately after their withdrawal.

Batu Khan, another grandson of Genghis Khan, overran the territories of the Bulgars, the Alans, the Kypchaks, Bashkirs, Mordvins, Chuvash, and other nations of the southern Russian steppe. By 1237 the Mongols were encroaching upon Ryazan, the first Kievan Rus' principality they were to attack. After a three-day siege involving fierce fighting, the Mongols captured the city and massacred its inhabitants. They then proceeded to destroy the army of the Grand Principality of Vladimir at the Battle of the Sit River.

The Mongols captured the Alania capital Maghas in 1238. By 1240, all Kievan Rus' had fallen to the Asian invaders except for a few northern cities. Mongol troops under Chormaqan in Persia , connecting his invasion of Transcaucasia with the invasion of Batu and Subutai, forced the Georgian and Armenian nobles to surrender as well.

Giovanni de Plano Carpini, the pope's envoy to the Mongol great khan, travelled through Kiev in February 1246 and wrote:

Despite the military successes, strife continued within the Mongol ranks. Batu's relations with Güyük, Ögedei's eldest son, and Büri, the beloved grandson of Chagatai Khan, remained tense and worsened during Batu's victory banquet in southern Kievan Rus'. Nevertheless, Güyük and Buri could not do anything to harm Batu's position as long as his uncle Ögedei was still alive. Ögedei continued with offensives into the Indian subcontinent, temporarily investing Uchch, Lahore, and Multan of the Delhi Sultanate and stationing a Mongol overseer in Kashmir, though the invasions into India eventually failed and were forced to retreat. In northeastern Asia, Ögedei agreed to end the conflict with Goryeo by making it a client state and sent Mongol princesses to wed Goryeo princes. He then reinforced his kheshig with the Koreans through both diplomacy and military force.

Push into central Europe

The advance into Europe continued with Mongol invasions of Poland and Hungary. When the western flank of the Mongols plundered Polish cities, a European alliance among the Poles, the Moravians, and the Christian military orders of the Hospitallers, Teutonic Knights and the Templars assembled sufficient forces to halt, albeit briefly, the Mongol advance at Legnica.

The Hungarian army, their Croatian allies and the Knights Templar were beaten by the Mongols at the banks of the Sajo River on 11 April 1241. Before Batu's forces could continue on to Vienna and northern Albania, news of Ögedei's death in December 1241 brought a halt to the invasion. As was customary in Mongol military tradition, all princes of Genghis's line had to attend the kurultai to elect a successor.

Batu and his western Mongol army withdrew from Central Europe the next year. Today researchers doubt that Ögedei's death was the sole reason for the Mongols withdrawal. Batu did not return to Mongolia, so a new khan was not elected until 1246. Climatic and environmental factors, as well as the strong fortifications and castles of Europe, played an important role in the Mongols' decision to withdraw.

Post-Ögedei power struggles (1241–1251)

Following the Great Khan Ögedei's death in 1241, and before the next kurultai, Ögedei's widow Töregene took over the empire. She persecuted her husband's Khitan and Muslim officials and gave high positions to her own allies. She built palaces, cathedrals, and social structures on an imperial scale, supporting religion and education. She was able to win over most Mongol aristocrats to support Ögedei's son Güyük. But Batu, ruler of the Golden Horde, refused to come to the kurultai, claiming that he was ill and that the climate was too harsh for him. The resulting stalemate lasted more than four years and further destabilized the unity of the empire.

When Genghis Khan's youngest brother Temüge threatened to seize the throne, Güyük came to Karakorum to try to secure his position. Batu eventually agreed to send his brothers and generals to the kurultai convened by Töregene in 1246. Güyük by this time was ill and alcoholic, but his campaigns in Manchuria and Europe gave him the kind of stature necessary for a great khan. He was duly elected at a ceremony attended by Mongols and foreign dignitaries from both within and without the empire — leaders of vassal nations, representatives from Rome, and other entities who came to the kurultai to show their respects and conduct diplomacy.

Güyük took steps to reduce corruption, announcing that he would continue the policies of his father Ögedei, not those of Töregene. He punished Töregene's supporters, except for governor Arghun the Elder. He also replaced young Qara Hülëgü, the khan of the Chagatai Khanate, with his favorite cousin Yesü Möngke, to assert his newly conferred powers. He restored his father's officials to their former positions and was surrounded by Uyghur, Naiman and Central Asian officials, favoring Han Chinese commanders who had helped his father conquer Northern China. He continued military operations in Korea, advanced into Song China in the south, and into Iraq in the west, and ordered an empire-wide census. Güyük also divided the Sultanate of Rum between Izz-ad-Din Kaykawus and Rukn ad-Din Kilij Arslan, though Kaykawus disagreed with this decision.

Not all parts of the empire respected Güyük's election. The Hashshashins, former Mongol allies whose Grand Master Hasan Jalalud-Din had offered his submission to Genghis Khan in 1221, angered Güyük by refusing to submit. Instead he murdered the Mongol generals in Persia. Güyük appointed his best friend's father Eljigidei as chief commander of the troops in Persia and gave them the task of both reducing the strongholds of the Nizari Ismailis and conquering the Abbasids at the center of the Islamic world, Iran and Iraq.

Death of Güyük (1248)

In 1248, Güyük raised more troops and suddenly marched westward from the Mongol capital of Karakorum. The reasoning was unclear. Some sources wrote that he sought to recuperate at his personal estate, Emyl; others suggested that he might have been moving to join Eljigidei to conduct a full-scale conquest of the Middle East, or possibly to make a surprise attack on his rival cousin Batu Khan in Kievan Rus.

Suspicious of Güyük's motives, Sorghaghtani Beki, the widow of Genghis's son Tolui, secretly warned her nephew Batu of Güyük's approach. Batu had himself been traveling eastward at the time, possibly to pay homage, or perhaps with other plans in mind. Before the forces of Batu and Güyük met, Güyük, sick and worn out by travel, died en route at Qum-Senggir (Hong-siang-yi-eulh) in Xinjiang, possibly a victim of poison.

Güyük's widow Oghul Qaimish stepped forward to take control of the empire, but she lacked the skills of her mother-in-law Töregene, and her young sons Khoja and Naku and other princes challenged her authority. To decide on a new great khan, Batu called a kurultai on his own territory in 1250. As it was far from the Mongol heartland, members of the Ögedeid and Chagataid families refused to attend. The kurultai offered the throne to Batu, but he rejected it, claiming he had no interest in the position. Batu instead nominated Möngke, a grandson of Genghis from his son Tolui's lineage. Möngke was leading a Mongol army in Rus, the northern Caucasus and Hungary. The pro-Tolui faction supported Batu's choice, and Möngke was elected; though given the kurultai's limited attendance and ___location, it was of questionable validity.

Batu sent Möngke, under the protection of his brothers, Berke and Tukhtemur, and his son Sartaq to assemble a more formal kurultai at Kodoe Aral in the heartland. The supporters of Möngke repeatedly invited Oghul Qaimish and the other major Ögedeid and Chagataid princes to attend the kurultai, but they refused each time. The Ögedeid and Chagataid princes refused to accept a descendant of Genghis's son Tolui as leader, demanding that only descendants of Genghis's son Ögedei could be great khan.

Rule of Möngke Khan (1251–1259)

When Möngke's mother Sorghaghtani and their cousin Berke organized a second kurultai on 1 July 1251, the assembled throng proclaimed Möngke great khan of the Mongol Empire. This marked a major shift in the leadership of the empire, transferring power from the descendants of Genghis's son Ögedei to the descendants of Genghis's son Tolui. The decision was acknowledged by a few of the Ögedeid and Chagataid princes, such as Möngke's cousin Kadan and the deposed khan Qara Hülëgü, but one of the other legitimate heirs, Ögedei's grandson Shiremun, sought to topple Möngke.

Shiremun moved with his own forces toward the emperor's nomadic palace with a plan for an armed attack, but Möngke was alerted by his falconer of the plan. Möngke ordered an investigation of the plot, which led to a series of major trials all across the empire. Many members of the Mongol elite were found guilty and put to death, with estimates ranging from 77 to 300, though princes of Genghis's royal line were often exiled rather than executed.

Möngke confiscated the estates of the Ögedeid and the Chagatai families and shared the western part of the empire with his ally Batu Khan. After the bloody purge, Möngke ordered a general amnesty for prisoners and captives, but thereafter the power of the great khan's throne remained firmly with the descendants of Tolui.

Administrative reforms

Möngke was a serious man who followed the laws of his ancestors and avoided alcoholism. He was tolerant of outside religions and artistic styles, leading to the building of foreign merchants' quarters, Buddhist monasteries, mosques, and Christian churches in the Mongol capital. As construction projects continued, Karakorum was adorned with Chinese, European, and Persian architecture. One famous example was a large silver tree with cleverly designed pipes that dispensed various drinks. The tree, topped by a triumphant angel, was crafted by Guillaume Boucher, a Parisian goldsmith.

Although he had a strong Chinese contingent, Möngke relied heavily on Muslim and Mongol administrators and launched a series of economic reforms to make government expenses more predictable. His court limited government spending and prohibited nobles and troops from abusing civilians or issuing edicts without authorization. He commuted the contribution system to a fixed poll tax which was collected by imperial agents and forwarded to units in need. His court also tried to lighten the tax burden on commoners by reducing tax rates. He also centralized control of monetary affairs and reinforced the guards at the postal relays. Möngke ordered an empire-wide census in 1252 that took several years to complete and was not finished until Novgorod in the far northwest was counted in 1258.

In another move to consolidate his power, Möngke assigned his brothers Hulagu and Kublai to rule Persia and Mongol-held China respectively. In the southern part of the empire he continued his predecessors' struggle against the Song dynasty. In order to outflank the Song from three directions, Möngke dispatched Mongol armies under his brother Kublai to Yunnan, and under his uncle Iyeku to subdue Korea and pressure the Song from that direction as well.

Kublai conquered the Dali Kingdom in 1253 after the Dali King Duan Xingzhi defected to the Mongols and helped them conquer the rest of Yunnan. Möngke's general Qoridai stabilized his control over Tibet, inducing leading monasteries to submit to Mongol rule. Subutai's son Uryankhadai reduced the neighboring peoples of Yunnan to submission and went to war with the kingdom of Đại Việt under the Trần dynasty in northern Vietnam in 1258, but they had to draw back. The Mongol Empire tried to invade Đại Việt again in 1285 and 1287 but were defeated both times.

New invasions of the Middle East and Southern China

After stabilizing the empire's finances, Möngke once again sought to expand its borders. At kurultais in Karakorum in 1253 and 1258 he approved new invasions of the Middle East and south China. Möngke put Hulagu in overall charge of military and civil affairs in Persia, and appointed Chagataids and Jochids to join Hulagu's army.

The Muslims from Qazvin denounced the menace of the Nizari Ismailis, a well-known sect of Shiites. The Mongol Naiman commander Kitbuqa began to assault several Ismaili fortresses in 1253, before Hulagu advanced in 1256. Ismaili Grand Master Rukn al-Din Khurshah surrendered in 1257 and was executed. All of the Ismaili strongholds in Persia were destroyed by Hulagu's army in 1257, except for Girdkuh which held out until 1271.

The center of the Islamic Empire at the time was Baghdad, which had held power for 500 years but was suffering internal divisions. When its caliph al-Mustasim refused to submit to the Mongols, Baghdad was besieged and captured by the Mongols in 1258 and subjected to a merciless sack, an event considered one of the most catastrophic events in the history of Islam, and sometimes compared to the rupture of the Kaaba. With the destruction of the Abbasid Caliphate, Hulagu had an open route to Syria and moved against the other Muslim powers in the region.

His army advanced toward Ayyubid-ruled Syria, capturing small local states en route. The sultan Al-Nasir Yusuf of the Ayyubids refused to show himself before Hulagu; however, he had accepted Mongol supremacy two decades earlier. When Hulagu headed further west, the Armenians from Cilicia, the Seljuks from Rum and the Christian realms of Antioch and Tripoli submitted to Mongol authority, joining them in their assault against the Muslims. While some cities surrendered without resisting, others, such as Mayafarriqin fought back; their populations were massacred and the cities were sacked.

Death of Möngke Khan (1259)

Meanwhile, in the northwestern portion of the empire, Batu's successor and younger brother Berke sent punitive expeditions to Ukraine, Belarus, Lithuania and Poland. Dissension began brewing between the northwestern and southwestern sections of the Mongol Empire as Batu suspected that Hulagu's invasion of Western Asia would result in the elimination of Batu's own dominance there.

In the southern part of the empire, Möngke Khan himself led his army, but did not complete the conquest of China. Military operations were generally successful, but prolonged, so the forces did not withdraw to the north as was customary when the weather turned hot. Disease ravaged the Mongol forces with bloody epidemics, and Möngke died there on 11 August 1259. This event began a new chapter in the history of the Mongols, as again a decision needed to be made on a new great khan. Mongol armies across the empire withdrew from their campaigns to convene a new kurultai.

Disunity

Dispute over succession

Möngke's brother Hulagu broke off his successful military advance into Syria, withdrawing the bulk of his forces to Mughan and leaving only a small contingent under his general Kitbuqa. The opposing forces in the region, the Christian Crusaders and Muslim Mamluks, both recognizing that the Mongols were the greater threat, took advantage of the weakened state of the Mongol army and engaged in an unusual passive truce with each other.

In 1260, the Mamluks advanced from Egypt, being allowed to camp and resupply near the Christian stronghold of Acre, and engaged Kitbuqa's forces just north of Galilee at the Battle of Ain Jalut. The Mongols were defeated, and Kitbuqa executed. This pivotal battle marked the western limit for Mongol expansion in the Middle East, and the Mongols were never again able to make serious military advances farther than Syria.

In a separate part of the empire, Kublai Khan, another brother of Hulagu and Möngke, heard of the great khan's death at the Huai River in China. Rather than returning to the capital, he continued his advance into the Wuchang area of China, near the Yangtze River. Their younger brother Ariqboke took advantage of the absence of Hulagu and Kublai, and used his position at the capital to win the title of great khan for himself, with representatives of all the family branches proclaiming him as the leader at the kurultai in Karakorum. When Kublai learned of this, he summoned his own kurultai at Kaiping, and nearly all the senior princes and great noyans in North China and Manchuria supported his own candidacy over that of Ariqboke.

Mongol Civil War

Battles ensued between the armies of Kublai and those of his brother Ariqboke, which included forces still loyal to Möngke's previous administration. Kublai's army easily eliminated Ariqboke's supporters and seized control of the civil administration in southern Mongolia. Further challenges took place from their cousins, the Chagataids. Kublai sent Abishka, a Chagataid prince loyal to him, to take charge of Chagatai's realm. But Ariqboke captured and then executed Abishka, having his own man Alghu crowned there instead. Kublai's new administration blockaded Ariqboke in Mongolia to cut off food supplies, causing a famine. Karakorum fell quickly to Kublai, but Ariqboke rallied and re-took the capital in 1261.

In southwestern Ilkhanate, Hulagu was loyal to his brother Kublai, but clashes with their cousin Berke, a Muslim and the ruler of the Golden Horde, began in 1262. The suspicious deaths of Jochid princes in Hulagu's service, unequal distribution of war booty, and Hulagu's massacres of Muslims increased the anger of Berke, who considered supporting a rebellion of the Georgian Kingdom against Hulagu's rule in 1259–1260. Berke also forged an alliance with the Egyptian Mamluks against Hulagu and supported Kublai's rival claimant, Ariqboke.

Hulagu died on 8 February 1264. Berke sought to take advantage and invade Hulagu's realm, but he died along the way, and a few months later Alghu Khan of the Chagatai Khanate died as well. Kublai named Hulagu's son Abaqa as new Ilkhan, and nominated Batu's grandson Möngke Temür to lead the Golden Horde. Abaqa sought foreign alliances, such as attempting to form a Franco-Mongol alliance against the Egyptian Mamluks. Ariqboqe surrendered to Kublai at Shangdu on 21 August 1264.

Campaigns of Kublai Khan (1264–1294)

In the south, after the fall of Xiangyang in 1273, the Mongols sought the final conquest of the Song dynasty in South China. In 1271, Kublai renamed the new Mongol regime in China as the Yuan dynasty and sought to sinicize his image as Emperor of China to win the control of the Chinese people. Kublai moved his headquarters to Khanbaliq, the genesis for what later became the modern city of Beijing. His establishment of a capital there was a controversial move to many Mongols who accused him of being too closely tied to Chinese culture.

The Mongols were eventually successful in their campaigns against (Song) China, and the Chinese Song imperial family surrendered to the Yuan in 1276, making the Mongols the first non-Chinese people to conquer all of China. Kublai used his base to build a powerful empire, creating an academy, offices, trade ports and canals, and sponsoring arts and science. Mongol records list 20,166 public schools created during his reign.

After achieving actual or nominal dominion over much of Eurasia and successfully conquering China, Kublai pursued further expansion. His invasions of Burma and Sakhalin were costly, and his attempted invasions of Đại Việt (northern Vietnam) and Champa (southern Vietnam) ended in devastating defeat, but secured vassal statuses of those countries. The Mongol armies were repeatedly beaten in Đại Việt and were crushed at the Battle of Bạch Đằng (1288).

Nogai and Konchi, the khan of the White Horde, established friendly relations with the Yuan dynasty and the Ilkhanate. Political disagreement among contending branches of the family over the office of great khan continued, but the economic and commercial success of the Mongol Empire continued despite the squabbling.

In 1274 and again in 1281, Kublai Khan invaded Japan on two separate occasions. However, he was not able to conquer Japan. In the period of the Mongol invasion, the battles of Bun'ei and Kōan were fought along the coast of Hakata Bay near modern-day Fukuoka.

Disintegration into competing entities

Major changes occurred in the Mongol Empire in the late 1200s. Kublai Khan, after having conquered all of China and established the Yuan dynasty, died in 1294. He was succeeded by his grandson Temür Khan, who continued Kublai's policies. At the same time the Toluid Civil War, along with the Berke–Hulagu war and the subsequent Kaidu–Kublai war, greatly weakened the authority of the great khan over the entirety of the Mongol Empire and the empire fractured into autonomous khanates, the Yuan dynasty and the three western khanates: the Golden Horde, the Chagatai Khanate and the Ilkhanate. Only the Ilkhanate remained loyal to the Yuan court but endured its own power struggle, in part because of a dispute with the growing Islamic factions within the southwestern part of the empire.

After the death of Kaidu, the Chatagai ruler Duwa initiated a peace proposal and persuaded the Ögedeids to submit to Temür Khan. In 1304, all of the khanates approved a peace treaty and accepted Yuan emperor Temür's supremacy. This established the nominal supremacy of the Yuan dynasty over the western khanates, which was to last for several decades. This supremacy was based on weaker foundations than that of the earlier Khagans and each of the four khanates continued to develop separately and function as independent states.

Nearly a century of conquest and civil war was followed by relative stability, the Pax Mongolica, and international trade and cultural exchanges flourished between Asia and Europe. Communication between the Yuan dynasty in China and the Ilkhanate in Persia further encouraged trade and commerce between east and west. Patterns of Yuan royal textiles could be found on the opposite side of the empire adorning Armenian decorations; trees and vegetables were transplanted across the empire; and technological innovations spread from Mongol dominions toward the West. Pope John XXII was presented a memorandum from the eastern church describing the Pax Mongolica: "... Khagan is one of the greatest monarchs and all lords of the state, e.g., the king of Almaligh (Chagatai Khanate), emperor Abu Said and Uzbek Khan, are his subjects, saluting his holiness to pay their respects." However, while the four khanates continued to interact with one another well into the 14th century, they did so as sovereign states and never again pooled their resources in a cooperative military endeavor.

Development of the khanates

In spite of his conflicts with Kaidu and Duwa, Yuan emperor Temür established a tributary relationship with the war-like Shan people after his series of military operations against Thailand from 1297 to 1303. This was to mark the end of the southern expansion of the Mongols.

When Ghazan took the throne of the Ilkhanate in 1295, he formally accepted Islam as his own religion, marking a turning point in Mongol history after which Mongol Persia became more and more Islamic. Despite this, Ghazan continued to strengthen ties with Temür Khan and the Yuan dynasty in the east. It was politically useful to advertise the great khan's authority in the Ilkhanate, because the Golden Horde in Rus had long made claims on nearby Georgia. Within four years, Ghazan began sending tribute to the Yuan court and appealing to other khans to accept Temür Khan as their overlord. He oversaw an extensive program of cultural and scientific interaction between the Ilkhanate and the Yuan dynasty in the following decades.

Ghazan's faith may have been Islamic, but he continued his ancestors' war with the Egyptian Mamluks, and consulted with his old Mongol advisers in his native tongue. He defeated the Mamluk army at the Battle of Wadi al-Khazandar in 1299, but he was only briefly able to occupy Syria, due to distracting raids from the Chagatai Khanate under its de facto ruler Kaidu, who was at war with both the Ilkhans and the Yuan dynasty.

Struggling for influence within the Golden Horde, Kaidu sponsored his own candidate Kobeleg against Bayan (r. 1299–1304), the khan of the White Horde. Bayan, after receiving military support from the Mongols in Rus, requested assistance from both Temür Khan and the Ilkhanate to organize a unified attack against Kaidu's forces. Temür was amenable and attacked Kaidu a year later. After a bloody battle with Temür's armies near the Zawkhan River in 1301, Kaidu died and was succeeded by Duwa.

Duwa was challenged by Kaidu's son Chapar, but with the assistance of Temür, Duwa defeated the Ögedeids. Tokhta of the Golden Horde, also seeking a general peace, sent 20,000 men to buttress the Yuan frontier. Tokhta died in 1312, though, and was succeeded by Ozbeg (r. 1313–41), who seized the throne of the Golden Horde and persecuted non-Muslim Mongols. The Yuan's influence on the Horde was largely reversed and border clashes between Mongol states resumed. Ayurbarwada Buyantu Khan's envoys backed Tokhta's son against Ozbeg.

In the Chagatai Khanate, Esen Buqa I (r. 1309–1318) was enthroned as khan after suppressing a sudden rebellion by Ögedei's descendants and driving Chapar into exile. The Yuan and Ilkhanid armies eventually attacked the Chagatai Khanate. Recognising the potential economic benefits and the Genghisid legacy, Ozbeg reopened friendly relations with the Yuan in 1326. He strengthened ties with the Muslim world as well, building mosques and other elaborate structures such as baths. By the second decade of the 14th century, Mongol invasions had further decreased. In 1323, Abu Said Khan (r. 1316–35) of the Ilkhanate signed a peace treaty with Egypt. At his request, the Yuan court awarded his custodian Chupan the title of commander-in-chief of all Mongol khanates, but Chupan died in late 1327.

Civil war erupted in the Yuan dynasty in 1328–29. After the death of Yesün Temür in 1328, Tugh Temür became the new leader in Khanbaliq, while Yesün Temür's son Ragibagh succeeded to the throne in Shangdu, leading to the civil war known as the War of the Two Capitals. Tugh Temür defeated Ragibagh, but the Chagatai khan Eljigidey (r. 1326–29) supported Kusala, elder brother of Tugh Temür, as great khan. He invaded with a commanding force, and Tugh Temür abdicated. Kusala was elected khan on 30 August 1329. Kusala was then poisoned by a Kypchak commander under Tugh Temür, who returned to power.

Tugh Temür (1304–32) was knowledgeable about Chinese language and history and was also a creditable poet, calligrapher, and painter. In order to be accepted by other khanates as the sovereign of the Mongol world, he sent Genghisid princes and descendants of notable Mongol generals to the Chagatai Khanate, Ilkhan Abu Said, and Ozbeg. In response to the emissaries, they all agreed to send tribute each year. Furthermore, Tugh Temür gave lavish presents and an imperial seal to Eljigidey to mollify his anger.

Rump states of the Mongol Empire

With the death of Ilkhan Abu Said Bahatur in 1335, Mongol rule faltered and Persia fell into political anarchy. A year later his successor was killed by an Oirat governor, and the Ilkhanate was divided between the Suldus, the Jalayir, Qasarid Togha Temür (d. 1353), and Persian warlords. Taking advantage of the chaos, the Georgians pushed the Mongols out of their territory, and the Uyghur commander Eretna established an independent state (Eretnids) in Anatolia in 1336. Following the downfall of their Mongol masters, the loyal vassal, the Armenian Kingdom of Cilicia, received escalating threats from the Mamluks and were eventually overrun in 1375.

Along with the dissolution of the Ilkhanate in Persia, Mongol rulers in China and the Chagatai Khanate were also in turmoil. The plague known as the Black Death, which started in the Mongol dominions and spread to Europe, added to the confusion. Disease devastated all the khanates, cutting off commercial ties and killing millions. The plague may have taken 50 million lives in Europe alone in the 14th century.

As the power of the Mongols declined, chaos erupted throughout the empire as non-Mongol leaders expanded their own influence. The Golden Horde lost all of its western dominions (including modern Belarus and Ukraine) to Poland and Lithuania between 1342 and 1369. Muslim and non-Muslim princes in the Chagatai Khanate warred with each other from 1331 to 1343, and the Chagatai Khanate disintegrated when non-Genghisid warlords set up their own puppet khans in Transoxiana and Moghulistan. Janibeg Khan (r. 1342–1357) briefly reasserted Jochid dominance over the Chaghataids. Demanding submission from an offshoot of the Ilkhanate in Azerbaijan, he boasted that "today three uluses are under my control".

However, rival families of the Jochids began fighting for the throne of the Golden Horde (Great Troubles, 1359–1381) after the assassination of his successor Berdibek Khan in 1359. The last Yuan ruler Toghan Temür (r. 1333–70) was powerless to regulate those troubles, a sign that the empire had nearly reached its end. His court's unbacked currency had entered a hyperinflationary spiral and the Han-Chinese people revolted due to the Yuan's harsh impositions. In the 1350s, Gongmin of Goryeo successfully pushed Mongol garrisons back and exterminated the family of Toghan Temür Khan's empress while Tai Situ Changchub Gyaltsen managed to eliminate the Mongol influence in Tibet.

Increasingly isolated from their subjects, the Mongols quickly lost most of China to the rebellious Ming forces and in 1368 fled to their heartland in Mongolia. After the overthrow of the Yuan dynasty the Golden Horde lost touch with Mongolia and China, while the two main parts of the Chagatai Khanate were defeated by Timur (Tamerlane) (1336–1405), who founded the Timurid Empire. However, remnants of the Chagatai Khanate survived; the last Chagataid state to survive was the Yarkent Khanate, until its defeat by the Oirat Dzungar Khanate in the Dzungar conquest of Altishahr in 1680. The Golden Horde broke into smaller Turkic-hordes that declined steadily in power over four centuries. Among them, the khanate's shadow, the Great Horde, survived until 1502, when one of its successors, the Crimean Khanate, sacked Sarai. The Crimean Khanate lasted until 1783, whereas khanates such as the Khanate of Bukhara and the Kazakh Khanate lasted even longer.

Military organization

The number of troops mustered by the Mongols is the subject of some scholarly debate, but was at least 105,000 in 1206. The Mongol military organization was simple but effective, based on the decimal system. The army was built up from squads of ten men each, arbans (10 people), zuuns (100), Mingghans (1000), and tumens (10,000).

The Mongols were most famous for their horse archers, but troops armed with lances were equally skilled, and the Mongols recruited other military specialists from the lands they conquered. With experienced Chinese engineers and a bombardier corps which was expert at building trebuchets, catapults and other machines, the Mongols could lay siege to fortified positions, sometimes building machinery on the spot using available local resources.

Forces under the command of the Mongol Empire were trained, organized, and equipped for mobility and speed. Mongol soldiers were more lightly armored than many of the armies they faced but were able to make up for it with maneuverability. Each Mongol warrior would usually travel with multiple horses, allowing him to quickly switch to a fresh mount as needed. In addition, soldiers of the Mongol army functioned independently of supply lines, considerably speeding up army movement. Skillful use of couriers enabled the leaders of these armies to maintain contact with each other.

Discipline was inculcated during a nerge (traditional hunt), as reported by Juvayni. These hunts were distinctive from hunts in other cultures, being the equivalent to small unit actions. Mongol forces would spread out in a line, surround an entire region, and then drive all of the game within that area together. The goal was to let none of the animals escape and to slaughter them all.

Another advantage of the Mongols was their ability to traverse large distances, even in unusually cold winters; for instance, frozen rivers led them like highways to large urban centers on their banks. The Mongols were adept at river-work, crossing the river Sajó in spring flood conditions with thirty thousand cavalry soldiers in a single night during the Battle of Mohi (April 1241) to defeat the Hungarian king Béla IV. Similarly, in the attack against the Muslim Khwarezmshah a flotilla of barges was used to prevent escape on the river.

Traditionally known for their prowess with ground forces, the Mongols rarely used naval power. In the 1260s and 1270s they used seapower while conquering the Song dynasty of China, though their attempts to mount seaborne campaigns against Japan were unsuccessful. Around the Eastern Mediterranean, their campaigns were almost exclusively land-based, with the seas controlled by the Crusader and Mamluk forces.

All military campaigns were preceded by careful planning, reconnaissance, and the gathering of sensitive information relating to enemy territories and forces. The success, organization, and mobility of the Mongol armies permitted them to fight on several fronts at once. All adult males up to the age of 60 were eligible for conscription into the army, a source of honor in their tribal warrior tradition.

Society

Law and governance

The Mongol Empire was governed by a code of law devised by Genghis, called Yassa, meaning "order" or "decree". A particular canon of this code was that those of rank shared much the same hardship as the common man. It also imposed severe penalties, e.g., the death penalty if one mounted soldier following another did not pick up something dropped from the mount in front. Penalties were also decreed for rape and to some extent for murder. Any resistance to Mongol rule was met with massive collective punishment. Cities were destroyed and their inhabitants slaughtered if they defied Mongol orders. Under Yassa, chiefs and generals were selected based on merit. The empire was governed by a non-democratic, parliamentary-style central assembly, called kurultai, in which the Mongol chiefs met with the great khan to discuss domestic and foreign policies. Kurultais were also convened for the selection of each new great khan.

The Mongols imported Central Asian Muslims to serve as administrators in China and sent Han Chinese and Khitans from China to serve as administrators over the Muslim population in Bukhara in Central Asia, thus using foreigners to curtail the power of the local peoples of both lands.

Religions

At the time of Genghis Khan, virtually every religion had found Mongol converts, from Buddhism to Christianity, from Manichaeism to Islam. To avoid strife, Genghis Khan set up an institution that ensured complete religious freedom, though he himself was a shamanist. Under his administration, all religious leaders were exempt from taxation and from public service.

Initially there were few formal places of worship because of the nomadic lifestyle. However, under Ögedei (1186–1241), several building projects were undertaken in the Mongol capital. Along with palaces, Ögedei built houses of worship for the Buddhist, Muslim, Christian, and Taoist followers. The dominant religions at that time were Tengrism and Buddhism, although Ögedei's wife was a Nestorian Christian.

Eventually, each of the successor states adopted the dominant religion of the local populations: the Mongol-ruled Chinese Yuan dynasty in the East (originally the Great Khan's ___domain) embraced Buddhism and Shamanism, while the three Western khanates adopted Islam.

Arts and literature

The oldest surviving literary work in the Mongolian language is The Secret History of the Mongols, which was written for the royal family some time after Genghis Khan's death in 1227. It is the most significant native account of Genghis's life and genealogy, covering his origins and childhood through to the establishment of the Mongol Empire and the reign of his son, Ögedei.

Another classic from the empire is the Jami' al-tawarikh, or "Universal History". It was commissioned in the early 14th century by the Ilkhan Ghazan Khan as a way of documenting the entire world's history, to help establish the Mongols' own cultural legacy.

Mongol scribes in the 14th century used a mixture of resin and vegetable pigments as a primitive form of correction fluid; this might be its first known usage.

The Mongols also appreciated the visual arts, though their taste in portraiture was strictly focused on portraits of their horses, rather than of people.

Science

The Mongol Empire saw some significant developments in science due to the patronage of the Khans. Roger Bacon attributed the success of the Mongols as world conquerors principally to their devotion to mathematics. Astronomy was one branch of science that the Khans took a personal interest in. According to the Yuanshi, Ögedei Khan twice ordered the armillary sphere of Zhongdu to be repaired (in 1233 and 1236) and also ordered in 1234 the revision and adoption of the Damingli calendar. He built a Confucian temple for Yelü Chucai in Karakorum around 1236 where Yelü Chucai created and regulated a calendar on the Chinese model. Möngke Khan was noted by Rashid al-Din as having solved some of the difficult problems of Euclidean geometry on his own and written to his brother Hulagu Khan to send him the astronomer Tusi. Möngke Khan's desire to have Tusi build him an observatory in Karakorum did not reach fruition as the Khan died on campaign in southern China. Hulagu Khan instead gave Tusi a grant to build the Maragheh Observatory in Persia in 1259 and ordered him to prepare astronomical tables for him in 12 years, despite Tusi asking for 30 years. Tusi successfully produced the Ilkhanic Tables in 12 years, produced a revised edition of Euclid's elements and taught the innovative mathematical device called the Tusi couple. The Maragheh observatory held around 400,000 books salvaged by Tusi from the siege of Baghdad and other cities. Chinese astronomers brought by Hulagu Khan worked there as well.

Kublai Khan built a number of large observatories in China and his libraries included the Wu-hu-lie-ti (Euclid) brought by Muslim mathematicians. Zhu Shijie and Guo Shoujing were notable mathematicians in Yuan China. The Mongol physician Hu Sihui described the importance of a healthy diet in a 1330 medical treatise.

Ghazan Khan, able to understand four languages including Latin, built the Tabriz Observatory in 1295. The Byzantine Greek astronomer Gregory Chioniades studied there under Ajall Shams al-Din Omar who had worked at Maragheh under Tusi. Chioniades played an important role in transmitting several innovations from the Islamic world to Europe. These include the introduction of the universal latitude-independent astrolabe to Europe and a Greek description of the Tusi-couple, which would later have an influence on Copernican heliocentrism. Choniades also translated several Zij treatises into Greek, including the Persian Zij-i Ilkhani by al-Tusi and the Maragheh observatory. The Byzantine-Mongol alliance and the fact that the Empire of Trebizond was an Ilkhanate vassal facilitated Choniades' movements between Constantinople, Trebizond and Tabriz. Prince Radna, the Mongol viceroy of Tibet based in Gansu province, patronized the Samarkandi astronomer al-Sanjufini. The Arabic astronomical handbook dedicated by al-Sanjufini to Prince Radna, a descendant of Kublai Khan, was completed in 1363. It is notable for having Middle Mongolian glosses on its margins.

Mail system

The Mongol Empire had an ingenious and efficient mail system for the time, often referred to by scholars as the Yam. It had lavishly furnished and well-guarded relay posts known as örtöö set up throughout the Empire. A messenger would typically travel from one station to the next, either receiving a fresh, rested horse, or relaying the mail to the next rider to ensure the speediest possible delivery. The Mongol riders regularly covered per day, better than the fastest record set by the Pony Express some 600 years later. The relay stations had attached households to service them. Anyone with a paiza was allowed to stop there for re-mounts and specified rations, while those carrying military identities used the Yam even without a paiza. Many merchants, messengers, and travelers from China, the Middle East, and Europe used the system. When the great khan died in Karakorum, news reached the Mongol forces under Batu Khan in Central Europe within 4–6 weeks thanks to the Yam.

Genghis and his successor Ögedei built a wide system of roads, one of which carved through the Altai mountains. After his enthronement, Ögedei further expanded the road system, ordering the Chagatai Khanate and Golden Horde to link up roads in western parts of the Mongol Empire.

Kublai Khan, founder of the Yuan dynasty, built special relays for high officials, as well as ordinary relays, that had hostels. During Kublai's reign, the Yuan communication system consisted of some 1,400 postal stations, which used 50,000 horses, 8,400 oxen, 6,700 mules, 4,000 carts, and 6,000 boats.

In Manchuria and southern Siberia, the Mongols still used dogsled relays for the Yam. In the Ilkhanate, Ghazan restored the declining relay system in the Middle East on a restricted scale. He constructed some hostels and decreed that only imperial envoys could receive a stipend. The Jochids of the Golden Horde financed their relay system by a special Yam tax.

Silk Road

The Mongol unification in 1206 and subsequent peace in the region allowed for trade routes to form through the Mongol Empire. The Mongols had a history of supporting merchants and trade. Genghis Khan had encouraged foreign merchants early in his career, even before uniting the Mongols. Merchants provided information about neighboring cultures, served as diplomats and official traders for the Mongols, and were essential for many goods, since the Mongols produced little of their own.

Mongol government and elites provided capital for merchants and sent them far afield, in an ortoq (merchant partner) arrangement. In Mongol times, the contractual features of a Mongol-ortoq partnership closely resembled that of qirad and commenda arrangements, however, Mongol investors were not constrained using uncoined precious metals and tradable goods for partnership investments and primarily financed money-lending and trade activities. Moreover, Mongol elites formed trade partnerships with merchants from Italian cities, including Marco Polo's family. As the empire grew, any merchants or ambassadors with proper documentation and authorization received protection and sanctuary as they traveled through Mongol realms. Well-traveled and relatively well-maintained roads linked lands from the Mediterranean basin to China, greatly increasing overland trade and resulting in some dramatic stories of those who travelled through what would become known as the Silk Road.

Western explorer Marco Polo traveled east along the Silk Road, and the Chinese Mongol monk Rabban Bar Sauma made a comparably epic journey along the route, venturing from his home of Khanbaliq (Beijing) as far as Europe. European missionaries, such as William of Rubruck, also traveled to the Mongol court to convert believers to their cause, or went as papal envoys to correspond with Mongol rulers in an attempt to secure a Franco-Mongol alliance. It was rare, however, for anyone to journey the full length of Silk Road. Instead, merchants moved products like a bucket brigade, goods being traded from one middleman to another, moving from China all the way to the West; the goods moved over such long distances fetched extravagant prices.

After Genghis, the merchant partner business continued to flourish under his successors Ögedei and Güyük. Merchants brought clothing, food, information, and other provisions to the imperial palaces, and in return the great khans gave the merchants tax exemptions and allowed them to use the official relay stations of the Mongol Empire. Merchants also served as tax farmers in China, Rus and Iran. If the merchants were attacked by bandits, losses were made up from local residents who were obliged to find the stolen goods.

Policies changed under the Great Khan Möngke. Because of money laundering and overtaxing, he attempted to limit abuses and sent imperial investigators to supervise the ortoq businesses. He decreed that all merchants must pay commercial and property taxes, and he paid off all drafts drawn by high-ranking Mongol elites from the merchants. This policy continued under the Yuan dynasty.

The fall of the Mongol Empire in the 14th century led to the collapse of the political, cultural, and economic unity along the Silk Road. Turkic tribes seized the western end of the route from the Byzantine Empire, sowing the seeds of a Turkic culture that would later crystallize into the Ottoman Empire under the Sunni faith. In the East, the Han Chinese overthrew the Yuan dynasty in 1368, launching their own Ming dynasty and pursuing a policy of economic isolationism.

Legacy

The Mongol Empire, at its height of the largest contiguous empire in history, had a lasting impact, unifying large regions. Some of these (such as eastern and western Russia, and the western parts of China) remain unified today. Mongols might have been assimilated into local populations after the fall of the empire, and some of their descendants adopted local religions. For example, the eastern khanate largely adopted Buddhism, and the three western khanates adopted Islam, largely under Sufi influence.

According to some interpretations, Genghis Khan's conquests caused wholesale destruction on an unprecedented scale in certain geographic regions, leading to changes in the demographics of Asia.

The non-military achievements of the Mongol Empire include the introduction of a writing system, a Mongol alphabet based on the characters of the Old Uyghur, which is still used in Mongolia today.

Some of the other long-term consequences of the Mongol Empire include:

• Moscow rose to prominence while it was still under the rule of the Mongol-Tatar yoke, some time after Russian rulers were accorded the status of tax collectors for the Mongols. The fact that the Russians collected tribute and taxes for the Mongols meant that the Mongols themselves rarely visited the lands which they owned. The Russians eventually gained military power, and their ruler Ivan III completely overthrew the Mongols and formed the Russian Tsardom. After the Great Stand on the Ugra River proved that the Mongols were vulnerable, the Grand Duchy of Moscow gained independence.

• Europe's knowledge of the known world was immensely expanded by the information which was brought back to it by ambassadors and merchants. When Columbus sailed in 1492, his mission was to reach Cathay, the land of the Grand Khan in China, and give him a letter from the monarchs Ferdinand II of Aragon and Isabella I of Castile.

• Some studies indicate that the Black Death which devastated Europe in the late 1340s may have traveled from China to Europe along the trade routes of the Mongol Empire. In 1347, the Genoese possessor of Caffa, a great trade emporium on the Crimean Peninsula, came under siege by an army of Mongol warriors under the command of Janibeg. After a protracted siege during which the Mongol army was reportedly withering from disease, they decided to use the infected corpses as a biological weapon. The corpses were catapulted over the city walls, infecting the inhabitants. The Genoese traders fled, transferring the plague via their ships into the south of Europe, from where it rapidly spread. The total number of deaths worldwide from the pandemic is estimated at 75–200 million with up to 50 million deaths in Europe alone.

• Western researcher R. J. Rummel estimated that 30 million people were killed by the Mongol Empire. Other researchers estimate that as many as 80 million people were killed, with 50 million deaths being the middle ground. The population of China fell by half during fifty years of Mongol rule. Before the Mongol invasion, the territories of the Chinese dynasties reportedly had approximately 120 million inhabitants; after the conquest was completed in 1279, the 1300 census reported that China's total population was roughly 60 million. While it is tempting to attribute this major decline in China's population solely to Mongol ferocity, today scholars have mixed opinions about this subject. Scholars such as Frederick W. Mote argue that the wide drop in numbers reflects an administrative failure to keep records rather than a de facto decrease, while others such as Timothy Brook argue that the Mongols reduced much of the south Chinese population, and very debatably the Han Chinese population, to an invisible status through cancellation of the right to passports and denial of the right to direct land ownership. This meant that the Chinese had to depend on and be cared for chiefly by Mongols and Tartars, which also involved recruitment into the Mongol army. Other historians such as William McNeill and David O. Morgan argue that the bubonic plague was the main factor behind China's demographic decline during this period.

• The Islamic world was subjected to massive changes as a result of the Mongol invasions. The population of the Iranian plateau suffered from widespread disease and famine, resulting in the death of up to three-quarters of its population, possibly 10 to 15 million people. Historian Steven Ward estimates that Iran's population did not reach its pre-Mongol levels again until the mid-20th century.

• Mesopotamia, for millennia a showplace and pinnacle of human civilization and achievement, was depopulated and pastoralized, never to resume its previous pre-eminence. In his Outline of History, H. G. Wells attributed this to a Mongol prejudice against urban life:

In this region Mesopotamia nomadism really did attempt, and really did to a very considerable degree succeed in its attempt, to stamp a settled civilized system out of existence. When Jengis Khan first invaded China, we are told that there was a serious discussion among the Mongol chiefs whether all the towns and settled populations should not be destroyed. To these simple practitioners of the open-air life the settled populations seemed corrupt, crowded, vicious, effeminate, dangerous, and incomprehensible; a detestable human efflorescence upon what would otherwise have been good pasture. They had no use whatever for the towns. **** But it was only under Hulagu in Mesopotamia that these ideas seem to have been embodied in a deliberate policy. The Mongols here did not only burn and massacre; they destroyed the irrigation system that had endured for at least eight thousand years, and with that the mother civilization of all the Western world came to an end.

• David Nicole states in The Mongol Warlords, "terror and mass extermination of anyone opposing them was a well tested Mongol tactic." About half of the Russian population may have died during the invasion. However, Colin McEvedy in Atlas of World Population History, 1978 estimates the population of Russia-in-Europe dropped from 7.5 million prior to the invasion to 7 million afterward. Historians estimate that up to half of Hungary's two million population were victims of the Mongol invasion. Historian Andrea Peto says that Rogerius, an eyewitness, said that "the Mongols killed everybody regardless of gender or age" and "the Mongols especially 'found pleasure' in humiliating women."

• One of the more successful tactics employed by the Mongols was to wipe out urban populations that refused to surrender. During the Mongol invasion of Rus', almost all major cities were destroyed. If they chose to submit, the people were generally spared, though this was not guaranteed. For example, the city of Hamadan in modern-day Iran was destroyed and every man, woman, and child executed by Mongol general Subadai, after surrendering to him but failing to have enough provisions for his Mongol scouting force. Several days after the initial razing of the city, Subadai sent a force back to the burning ruins and the site of the massacre to kill any inhabitants of the city who had been away at the time of the initial slaughter and had returned in the meantime. Mongol armies made use of local peoples and their soldiers, often incorporating them into their armies. Prisoners of war sometimes were given the choice between death and becoming part of the Mongol army to aid in future conquests. Due to the brutal methods employed to subdue their subjects, Mongols maintained long lasting resentment from those they conquered. This resentment towards the Mongol rule has been highlighted as a cause for the empire's rapid fracturing. In addition to intimidation tactics, the rapid expansion of the empire was facilitated by military hardiness (especially during bitterly cold winters), military skill, meritocracy, and discipline.

• The Kalmyks were the last Mongol nomads to penetrate European territory, having migrated to Europe from Central Asia at the turn of the 17th century. In the winter of 1770–1771, approximately 200,000 Kalmyks began the journey from their pastures on the left bank of the Volga River to Dzungaria, through the territories of their Kazakh and Kyrgyz enemies. After several months of travel, only one-third of the original group reached Dzungaria in northwest China.

國號

以族名為國號

蒙古的國號與族名相關，原稱為「哈木黑蒙古」（漢譯為「蒙兀國」），成吉思汗統一蒙古高原後自號「也克蒙古兀魯思」（「大蒙古國」），該名此後在各種語言中沿用。

建「大元」國號

至元八年十一月十五日（1271年12月18日），在進攻南宋取得不斷勝利的形勢下，元世祖採納劉秉忠、王磐等漢臣建議，建「大元」國號，《建國號詔》曰：「可建國號曰『大元』，蓋取《易經》『乾元』之義。」其意為「極大」，表明本朝疆土超過以前所有的王朝。元朝建號以後，原「大蒙古國」國號在漢文文書中不再使用，但蒙文文書中通常兩者並稱為「大元大蒙古國」（八思巴文：，轉寫：）。

元朝時，「大一統」的觀念掀開了新的一頁。元朝的中外觀念是一體的中外觀。元吳師道詩：「今日八荒同一宇，向來邊檄不須論。」把原來視為外的地區「比於內地」，即元朝視全國為「內地」，包括中原、邊疆各民族在內。蒙古文史籍中指蒙古及其周圍地區為「五色四夷國」（）。一說出自佛教的「五方色」，指東方黃，南方赤，西方白，北方黑，中央青。《大黃史》等書稱，五色者，青蒙古，白肅良合（高麗），黃撒爾塔兀勒（回回），紅契丹（漢人），黑吐蕃（藏人）；四夷者，謂後四者為青蒙古之屬國。並認為五色四夷均出自一位君主。成吉思汗征服周圍地區和民族，即謂收撫五色四夷國。可見是指居中的青色蒙古及周鄰國家和民族，反映了蒙古帝國中後期蒙古人的世界觀和民族觀。

歷史

蒙古源流

源出室韋

蒙古部落的名稱最早出現於唐代。那時，在狃越河（今洮兒河）以北，西至俱輪泊（今呼倫湖）周圍，東至那河（今嫩江），北至黑龍江的地域內，分布著許多許多被統稱為「室韋」的大小部落，其中有一個「蒙兀室韋」部。蒙兀就是蒙古（Monggol）的唐代音譯。《舊唐書·北狄·室韋傳》記載：「大山之北有大室韋部落，其部落傍望建河居。其河源出突厥東北界俱輪泊，屈曲東流，經西室韋界，又東經大室韋界，又東經蒙兀室韋之北，落俎室韋之南。」

大山指今大興安嶺，望建河即今額爾古納河。根據這段史料，蒙兀室韋部的居地應在額爾古納河下游東南的大興安嶺北端地區。十三世紀蒙古人的歷史傳說稱，他們的祖先原來居住在名為「額爾古納昆」（Ergunequn，qun意為山崖）的地方，應是指額爾古納河附近的山林地帶，和漢文史籍所載唐代蒙兀部的居地正可以相互印證。

大約在唐代後期（九世紀下半葉），蒙古部落從興安嶺山地向西面的草原地帶遷移。隨部落的分行，所佔地盤逐漸擴大，有一部分遷到了鄂嫩河、克魯倫河、土拉河「三河之源」的不兒罕山（今肯特山）地區。成吉思汗的先世就屬於這部分蒙古部落。

蒼狼白鹿

元代史籍記載下來的蒙古人祖先傳說，反映了古代蒙古部落繁衍和遷徙的歷史過程。《元朝秘史》一開頭就講述蒙古人的起源，說是有一奉天命降生的蒼色的狼（孛兒帖赤那，Bortechino）和一白色的母鹿（豁埃馬闌勒，qo'ai-maral）相配了，渡過騰汲思海子，來到斡難河（鄂嫩河）源頭的不兒罕山立下營盤，生了個兒子名巴塔赤罕。傳到第十一代，有兄弟二人，兄都蛙鎖豁兒有四子，遷移出去成為朵兒邊部（Dorben，意為四）；弟朵奔篾兒幹娶豁里禿馬惕部女子阿蘭豁阿為妻，生二子，其後裔各成一部。朵奔死後，阿蘭豁阿感天光而孕，又生三子，長不忽合塔吉，後裔為合答斤部（名見《金史》，作合底忻），次不合禿撒勒只，後裔為撒勒只兀惕部（名見《金史》，作山只昆，元代又譯散只兀，珊竹）；幼子孛端察兒，後裔為孛兒只斤部，從這一支又分衍出約二十個氏族或部落。孛端察兒就是成吉思汗的十世祖，《元史·宗室世系表》稱為「始祖」。

阿蘭死後，兩個大兒子的子孫同其他各支蒙古人組成了蒙古迭兒列斤氏部落，即一般出身的蒙古人；三個小兒子的子孫組成了尼倫部落，因為他們是閃耀著神的光輝的後代，因此被看作純潔出身的蒙古人。其中第五子孛端察兒的後代稱為孛兒只斤氏，這就是成吉思汗所出生的氏族。

合木黑蒙古

十一世紀時，居住在大漠南北的塔塔兒、蒙古、克烈、汪古等部結成以塔塔兒為首的聯盟，共同反對遼王朝的統治，因此，「塔塔兒」或「韃靼」曾一度成為蒙古草原上各部的通稱。十二世紀初，由女真貴族建立的金王朝取代了遼王朝，蒙古部轉歸金朝東北招討使管轄。這時塔塔兒聯盟已經瓦解，蒙古部在合不勒汗（成吉思汗曾祖父）的統領下強大起來。合不勒汗（生卒年不詳）又作「葛不律寒」、「哈不勒罕」。蒙古孛兒只斤部首領，成吉思汗曾祖父。以乞顏為氏，統一蒙古部，始稱汗，被尊為「全體蒙古人」（合木黑忙豁勒）的首領。

當時金朝的皇帝是金太宗完顏晟（1123年—1135年在位），他想籠絡合不勒汗，便派人請合不勒汗到金國宮中，設宴招待。在這次著名的宴會上，合不勒汗抓住金帝的鬍子，肆意戲弄，導致蒙、金關係迅速惡化，金帝便利用塔塔兒部幾次攻打蒙古。最初金熙宗乃用其將領完顏宗弼之謀，誅其臣完顏昌，完顏昌遺族遂與合不勒進攻金人於漠北，金將完顏宗弼屢次征伐而不能克，從此金人北受蒙古之侵襲，而不能用全力南侵中國。金主於宋紹興十六年（1146年）八月，調功臣皇叔完顏宗弼由南線回朝。奉命親率中原精兵8萬之眾，出征蒙古，大小數十仗，屢戰不勝，不得不於宋紹興十七年（1147年）三月，與蒙古訂立協議議和，並把西平以北27團寨，割與蒙古，每年供應蒙古相當數額的牛羊米豆，並冊封合不勒汗為「蒙兀國王」，才得罷兵修好。

蒙古可汗合不勒死後，姪兒俺巴孩被推選為可汗。俺巴孩與塔塔兒部結親，為女兒送嫁途中，被塔塔兒部的主因人俘虜，送給了金熙宗。金熙宗將俺巴孩釘死在木驢上。合不勒之子忽圖剌繼而當選為可汗，率部向塔塔兒人發動復仇的戰爭，然而前後十三次開戰，也未能替俺巴孩可汗報仇。宋紹興三十二年（1162年），忽圖剌的姪兒，乞顏部的也速該帶領部眾攻打塔塔兒人，取得了勝利，並且活捉了塔塔兒人豁里不花與鐵木真兀格。鐵木真兀格是一位勇士，也速該心存敬仰，便把他放了。當也速該返回鄂嫩河邊的營地時，夫人訶額崙生下一個男孩，也速該十分高興，索性將孩子取名為鐵木真，這便是日後的蒙古大汗——成吉思汗。

鐵木真9歲時父親也速該被塔塔兒部人毒死，孛兒只斤氏族族眾離散。最後導致合木黑蒙古國的分裂：以泰赤烏部首領塔里忽台為首佔據鄂嫩河流域；以札達蘭部的札木合為首佔據額爾古納河流域；主兒乞部撒察別乞、台出為首佔據鄂嫩，克魯倫河流域。宋淳熙十六年（1189年），也速該的兒子鐵木真恢復了合木黑蒙古國，但是鬥爭仍未結束。

鐵木真統一漠北

蒙古部族的原居地為今黑龍江上游、蒙古東部，為唐時室韋部落之一，稱蒙兀室韋，亦有說是出於韃靼，甚至是匈奴或吐蕃的後裔。現今，東胡說已成為蒙古族起源的主流學說。南宋前期，蒙古分為許多單位，其中之一為乞顏部，據今土拉河、鄂嫩河、克魯倫河上源的肯特山。其他重要部族，在東方為貝爾湖附近的塔塔兒，在西方為蒙古中部的蔑兒乞、克烈，及科布多一帶的乃蠻，名義上大都臣服於金朝，形貌語言風俗習慣迷信大致相類。其間部眾最多者，為乃蠻部落，居也兒的石河上流，及大金（阿爾泰）山脈連亙之地。西隔一沙漠，與突厥種之畏兀兒相接。北界小金山與突厥種之乞兒吉思謙謙州兩部之地為鄰。東界哈剌和林諸山，與克烈部連界。時克烈之居地達於斡難怯綠連兩河之源，克烈部以北之地屬蔑兒乞部。別有斡亦剌部，則據有構成昔之謙河（今名葉尼塞河）之八水灌溉之地。札剌兒部分為十部，部各有長，結幕於鄂嫩河畔，共有七十千戶塔塔兒部居女真舊境邊界附近，捕魚兒湖一帶。

十二世紀，蒙古草原部落林立，互相攻劫，人不安生。經過長期的戰爭兼併，至十二世紀末葉，形成了塔塔兒、克烈、蒙古、蔑兒乞、乃蠻等相互結仇很深的五大部落集團，雄據南方的金朝也已衰弱，為蒙古統一提供了有利條件。鐵木真9歲時，其父也速該被塔塔兒人毒死。殘酷的現實使鐵木真認識到，要保存自己，恢復祖業，就要依靠和聯合一個強大的部落。於是在其父的「安答」克烈部首領脫里罕庇護下，收集離散部眾，力量逐漸強大。宋淳熙十六年（1189年），被推舉為汗。

鐵木真稱汗後，為增強經濟和軍事實力，鞏固汗權，展開了奪取東部地區的鬥爭，宋慶元元年（1195年）和宋慶元二年（1196年），金朝兩次出兵攻打塔塔兒部，鐵木真聯合克烈部助金朝大敗塔塔兒於活勒札河（今烏力吉河），在回軍途中攻滅背叛盟約，抄掠其奧魯（老小營）的主兒勤部。鐵木真既獲得金的封賞，又消滅了與之爭奪汗位的乞顏氏中的長支貴族，名聲大振。

宋慶元四年（1198年），金朝又遣軍征討弘吉剌、合答斤、山只昆等部。金朝的這幾次征伐，為鐵木真奪取富饒的呼倫貝爾草原掃清了障礙，鐵木真的實力迅速增強，引起貴族們的敵視，開始了與貴族聯盟的一系列戰役，最初由只剌札木合糾集泰赤烏等十三部3萬軍進攻鐵木真，鐵木真汗組成十三翼（古列延）迎戰於鄂嫩河附近的答蘭版朱思。鐵木真失利。後魯的主兒扯歹、忙兀部的畏答兒、晃勒壇的蒙力克率部歸附鐵木真，鐵木真力量日益壯大。

宋慶元六年（1200年），弘吉剌、朵兒邊、塔塔兒等十一部復聚會於阿雷泉，盟誓與鐵木真、王罕為敵。鐵木真得到其岳父的密告，乃會同王罕與十一部聯軍戰於捕魚兒海子（貝爾湖）附近，貴族聯軍大敗。翌年，被擊敗的貴族們再聚刊河（今根河），推札木合為「古兒罕」 ，誓與鐵木真為敵。鐵木真認真備戰，與王罕軍於海剌兒河（今海拉爾河）附近再敗貴族聯軍，鐵木真為鞏固後方趁勢攻滅了察罕塔塔兒、按赤塔塔兒等部，完全佔據呼倫貝爾草原。

宋嘉泰二年（1202年）秋，闊亦田（約在哈拉哈河上游）之戰，又大敗由乃蠻杯祿汗拼湊起來的斡亦剌、泰赤烏、塔塔兒等部殘餘勢力的聯軍，札木合率部投王罕。至此，結束了與貴族聯盟之戰，鐵木真與克烈部王罕長期結盟。不久王罕背盟，加上札木合等的離間，鐵木真與王罕關係惡化。鐵木真曾欲以聯姻修補裂痕，遭到拒絕，王罕、札木合等設計謀殺鐵木真未成，又突襲之。鐵木真倉卒應戰於合蘭真沙陀（約今烏珠穆沁旗北境），因眾寡不敵，退至合合河（今哈拉哈河）上游整軍。此時，札木合等與王罕分裂，鐵木真偵知王罕無備，秘密包圍，激戰三晝夜，王罕父子敗逃，先後被殺。鐵木真獲得從未有過的勝利。

最後一個對手是乃蠻。為準備與乃蠻的決戰，鐵木真按千戶制組編軍隊，設扯兒必那顏（統領）統率；又成立護衛軍，設80宿衛，70散班（魯華），軍隊更加強大。宋嘉泰四年（1204年），納忽山之戰中乃蠻軍一觸即潰，太陽汗負傷死，鐵木真進抵阿爾泰山前，盡降其餘部，完成了統一漠北諸部的大業，為大蒙古國和以後元朝的大發展奠定了基礎。

鐵木真征服乃蠻部後，為追擊王罕之子桑昆，為進攻金朝，解除對翼側的牽制，向西夏伸出觸角進行試探。蒙古軍於宋開禧元年（1205年）三月，從也兒的失河不黑都兒麻地區回軍，經察罕泊、鄂洛克泊南下，進至西夏居延海（今內蒙古額濟納旗）東南50里處圍攻力吉里寨。該寨修築堅固，但蒙古軍在短時間內攻克，並將寨牆和基礎全部平毀。接著分兵進攻瓜州（今甘肅安西北部）、沙州（今甘肅敦煌）等地，又東攻定州（今內蒙古阿拉善左旗）之乞鄰古古撒城和龍州（今內蒙古臨河）落思城。掃蕩黃河西岸、北岸，帶著許多戰利品和駱駝、牲畜後還軍鄂嫩河。

大蒙古國建立

元太祖元年（1206年）春，鐵木真下令建九腳白旄纛，在鄂嫩河源頭召開忽里勒台，即皇帝位，建立大蒙古國（蒙古語「也可·蒙古·兀魯思」）。薩滿教巫師闊闊出聲稱得到上天的啟示，命鐵木真為普天下之汗、諸王之王，諸王群臣共上尊號稱他為「成吉思皇帝」。成吉思一詞的含義，有「海洋」、「有力」、「天賜」、「偉大」等諸多不同說法。此後，成吉思汗邁出了建立封建統治秩序的步伐。他將千百戶制度普遍推行於蒙古各部，以千戶、百戶、十戶的形式把全體蒙古人民組織起來，並封那些有功的那可兒們為千、百、十戶長，進行統管，且其職位世襲，史稱「莎余兒合勒」（即恩賜、分封之意）。這樣，千戶便成為蒙古社會最基本的行政軍事單位。不僅如此，成吉思汗還把蒙古國的臣民百姓視為自己的家產，除自己直接管領一部分人外，其餘部民均分封給自己的母親和兄弟子，他們每人得到若干千戶，稱為「忽必」。與此同時，成吉思汗還擴建了原有的怯薛（護衛軍），形成了一支由其直接掌管的萬人常備軍，其中包括千名宿衛士、千名箭筒士及八千名散班。這些官兵均由各級那顏及平民的子弟擔任，他們自備馬匹、武器和給養，而且還可以隨身帶有自己的「伴當」。因此，這些「怯薛」（護衛士）的身份往往高於在外的千戶長。除此之外，成吉思汗通過創制蒙古文字、設立也可扎魯忽赤（「扎魯忽赤」漢譯為「斷事官」）及編定《大札撒》等措施，建立起了大蒙古國的封建統治制度。至此，蒙古族的遊牧宗法奴隸制開始向宗法封建制度轉化和過渡。

成吉思汗建國以前，蒙古人還沒有文字。成吉思汗俘獲畏兀兒人塔塔統阿後，因他精通本國文字，就命他教子弟學習。其後又有不少畏兀兒人被用為蒙古貴族子弟的教師，他們對蒙古文的創製做出了貢獻。成吉思汗建立大蒙古國之前，蒙古沒有成文的法規，人們遵行的只是傳統慣法。大蒙古國建立後，創制畏兀兒蒙古文，成吉思汗就用它發布命令、登記戶口、制定了具體的法律條款，稱為《大札撒》（漢譯作《成吉思汗法典》、《成吉思汗大法》）、記錄所辦案件等，成為加強統治的重要輔助手段。《成吉思汗法典》頒布實施於元太祖元年（1206年），是世界上應用範圍最廣的成文法典，也是世界上最早的憲法性文件。《成吉思汗法典》建立了以民主為基礎的行政權與司法權分立的共和政體和一系列制度，其中，以兩權制約為基礎的判例制度比英國的判例制度產生早近600年。

元太祖元年（1206年），成吉思汗任命其養子失吉忽圖忽為大斷事官。由大斷事官專門負責掌管民戶的分配。成吉思汗又命失吉忽圖忽審斷刑獄詞訟，負責懲治盜賊、察明詐偽、施以刑法。大斷事官實際上是大蒙古國的最高行政官，相當於漢族官制中的丞相。大斷事官之下還有若干斷事官作為僚屬。此外諸王、貴戚、功臣有分地者，也各置斷事官治其本部百姓。

對外擴張

征西夏

成吉思汗在建國前的宋開禧元年（1205年），率軍第一次入侵西夏。這次只是小規模的掠奪。元太祖二年（1207年）秋，成吉思汗藉口西夏不肯稱臣納貢，再次興兵，攻陷西夏北部重鎮斡羅孩城。一年後的元太祖四年（1209年），成吉思汗第三次發兵，抵斡羅孩西關口。當時西夏皇帝為夏襄宗李安全，他令皇子李承禎為元帥，大都督府主高逸為副，率兵五萬抵擋，大敗，高逸被俘而死。蒙古軍再攻斡羅孩城，守將出降，太傅西壁訛答在城內堅持巷戰，仍不免力屈被俘。蒙古軍長驅直入，進逼中興府的外圍要隘克夷門（賀蘭山關口）。李安全急令嵬名令公率軍五萬拒戰。嵬名令公堅持了兩個月，最後中了蒙古軍的埋伏，兵敗被擒。克夷門既下，蒙古軍進抵都城中興府。成吉思汗派遣所俘的西壁訛答太傅入中興府談判，曉以利害。李安全自知難與蒙古軍為敵，遂將女兒察合公主獻給成吉思汗，表示願降蒙古，歲歲進貢，聯蒙抗金。至此，成吉思汗實現了他的戰略目標，他得以專心進攻更主要的敵國──金朝。屈辱的求和，加劇了西夏統治集團內部的鬥爭。不久，李安全被廢而死，他的堂侄李遵頊被立為帝，是為夏神宗。但在夏神宗之後，西夏仍然不能有效地抵禦剽悍的蒙古騎兵，在成吉思汗四海揚威之際，終至亡國。

成吉思汗的三次征西夏，掠奪了大量人口、財物以及牛羊、駱駝等，同時也鍛煉了軍隊，更重要的是戰略上取得了偉大勝利，他雖然沒有徹底征服西夏，但卻使西夏內部產生了動蕩不安，矛盾加深，因而造成政權一再更迭，國力大衰，沒有能力與蒙古人抗衡，進而動搖了夏金聯盟，解除了西夏對蒙古國的威脅。從此以後，成吉思汗集中全部精力和全部力量，來對付他的主要敵人金王朝了。但從元太祖十一年（1216年）起，由於成吉思汗在進攻金朝和西征西遼的過程中，不斷向西夏徵兵、收貢，使西夏統治者感到負擔十分沉重，於是對蒙古漸漸疏遠。這樣，又引起蒙古的不滿，侵西夏的戰爭又爆發了。

元太祖十二年（1217年），成吉思汗封大將木華黎為太師國王，率軍侵金。木華黎南下進攻金朝的同時，又一次派軍隊攻打西夏。當年十二月，蒙古軍踏冰渡過黃河，長驅直入，很快包圍了中興府，夏神宗李遵頊心驚肉跳，帶著幾個手下人和嬪妃逃到西平府（即靈州），讓太子李德任守城。面對強敵，西夏軍無力抵抗，李德任不得不向蒙古軍隊請降，蒙古軍隊勝利，木華黎率軍隊返回金朝戰場。元太祖十六年（1221年）十月，木華黎由東勝渡河，準備經過西夏，進攻金朝的陝西地方。李遵頊惶恐不已，急忙派大臣塔海去迎接木華黎，又派塔哥甘普領兵五萬，追隨木華黎進攻金朝。心力交瘁的李遵頊無力支撐危局，於元太祖十八年（1223年）把王位讓給次子李德旺，自稱太上皇隱退。李德旺即位後深感蒙古勢力的可怕，想乘成吉思汗西征之機，聯合漠北諸部落，組成抗擊蒙古的聯盟。當時成吉思汗正率軍西征花剌子模國，得悉西夏「陰結外援，蓄異圖」的密報後，雖知情況緊急，無奈戰事正緊，無法脫身，故令木華黎之子（木華黎已去世）孛魯，迅速從金朝回兵進攻西夏。元太祖十九年（1224年）九月，蒙古軍襲擊西夏，大破銀州（今陝西榆林南），夏兵10萬人戰死，守將塔海被俘後遭到殺害，蒙古軍擄掠牲口、牛羊達數十萬之多。西夏主李德旺不得不再次向蒙古表示臣服，蒙古軍退走。西夏在蒙古軍隊的一再打擊下，離最後的覆亡已為期不遠了。

征金

元太祖六年（1211年）秋，金朝邊境烏沙堡（在今內蒙古鑲黃旗境內）遭到成吉思汗的大將哲別的進攻。金兵統帥獨吉思忠領兵抵禦，戰敗退兵，蒙古軍乘勝而進。從此拉開了成吉思汗攻金的序幕。金是蒙古諸部的宗主國，成吉思汗曾助金擊滅塔塔兒，以獲得金帝所授「察忽魯」（部長）之職為榮耀，在他即大汗位之後，仍每年親自赴金邊境入貢。金又是蒙古的世仇，俺巴孩汗、斡勤巴兒合黑、合答安把阿禿兒等都慘死於金人之手，成吉思汗常「念其欺凌」，誓為復仇。元太祖三年（1208年），金章宗死，衛紹王完顏永濟即位，即位之後，他向蒙古遣使下詔書，要求成吉思汗跪拜接受。成吉思汗問：「誰是新皇帝？」金使答：「衛王。」成吉思汗南面而唾，說：「我以為中原的皇帝是天上人做，這等庸懦之輩也配嗎？豈能向他跪拜！」言罷策馬北。完顏永濟從金使那裡聽到這個消息，便陰謀趁成吉思汗下次入貢殺之。成吉思汗得到密報，遂與金朝絕交，嚴兵設備，並於元太祖六年（1211年）先發制人，親率大軍南下，於是有了烏沙堡擊敗金將獨吉思忠之役。金兵潰敗，獨吉思忠以失於防禦被解職，由完顏承裕主持軍事。完顏承裕不敢正面抗擊蒙古軍，一路撤退，退至宣平（今河北張家口市西南），以大軍三十萬守野狐嶺（今河北萬全縣膳房堡北）。成吉思汗命木華黎為蒙古軍先鋒，他策馬橫戈，大呼陷陣，成吉思汗繼以諸軍並進。金兵大敗，死者枕藉，整個原野都充滿了血腥氣味。成吉思汗追擊潰敗的金兵至會河堡（今河北懷安縣東），再殲金兵無數，完顏承裕隻身逃入宣德（今河北宣化縣）。野狐嶺之戰，「金人精銳盡沒」，蒙古人終於取得了進攻金朝的第一場大勝仗，他們以此為榮，很久以後還常常提起這件事。

元太祖七年（1212年），成吉思汗再次大舉南侵，攻佔昌州、桓州、撫州，再攻金西京。因金將固守，蒙古軍退回。又攻金東京遼陽府，擄掠而去。元太祖八年（1213年）秋，成吉思汗自陰山進軍，經宣德州至懷來，大敗金完顏綱軍。乘勝進居庸關，威脅中都。蒙古軍兵分三路攻掠黃河以北的山東、河東、河北路州縣，直抵登州（今山東蓬萊）、萊州（今山東掖縣）海濱。元太祖九年（1214年）春，擄掠大批財物後又返回居庸關一帶，圍攻中都。金宣宗南遷金軍敗退，朝中混亂。駐守中都城北的右副元帥紇石烈執中在元太祖八年（1213年）八月殺衛紹王完顏永濟，迎立金世宗孫完顏珣繼帝位（金宣宗）。元太祖八年（1213年）九月，金宣宗完顏珣遣使向蒙古軍求和。元太祖九年（1214年）三月，中都被圍，金宣宗獻納人口財物，並將衛紹王女岐國公主獻給成吉思汗。成吉思汗許和退軍。元太祖九年（1214年）五月，金宣宗深恐蒙軍再侵，率皇室百官，運載珠寶財物，遷都到南京（開封）。成吉思汗得知金朝遷都南逃，再次統兵南下。元太祖十年（1215年）春，蒙古軍陸續收降中都附近州縣金朝將官，擊敗前來救援中都的金軍。元太祖十年五月初二日（1215年5月31日），完顏承暉眼看中都解圍無望，服毒自殺，抹撚盡忠棄城出逃。蒙古軍遂入中都。成吉思汗當時在桓州涼涇避暑，聞報後命石抹明安鎮守中都，遣失吉忽圖忽等登錄中都帑藏，悉載以去。是年，中都與遼東、河北、山東860餘城，皆為蒙古軍攻佔。

中原山東、河北地區接連爆發武裝起義，而一些地主豪強也趁機擁兵自保，出現了武裝割據的局面。元太祖十二年（1217年），成吉思汗封其大將木華黎為太師國王，命他專統大軍攻金。其間，木華黎很注重利用漢族地主武裝的作用，而且除殺掠之外，開始注意佔據城邑、安集百姓而行經久之計。而金朝面臨蒙古軍強大的攻勢，又興兵南下侵宋，以求得補償。但在數年的戰爭中，金在宋、蒙古與西夏的聯合進攻下，國勢日衰，陷孤立之中。而木華黎大量招降反金的漢族武裝力量，幾年中，攻取了金之遼東、遼西、山東、河北、陝西等大片土地。木華黎死後，金哀宗停止南侵宋朝，集中兵力抵抗蒙古，曾收復了絳州、平陽、太原府。但為時已晚，成吉思汗完成西征，已回師中原。元太祖二十二年（1227年），滅西夏，拒金求和，進軍鳳翔府及京兆府，關中震動。成吉思汗死後，金軍雖小有勝績，但仍無力挽回敗局。

納金人才

佔領金中都在戰略上的意義自不待言，除此之外，蒙古帝國還有另外一個重要收獲，那就是耶律楚材（1190年－1244年）的投順。在對金戰爭中，成吉思汗很注意延攬金統治下原遼朝的遺民，著力將其收為己用。耶律楚材家族原為遼朝貴族東丹王後裔，且又長期在金朝擔任高官，地位與聲望皆十分顯赫。蒙古兵圍中都之時，耶律楚材適在中都，因而受到成吉思汗的注意。耶律楚材於「戊寅之春，三月既望」即元太祖十三年（1218年）受成吉思汗召，於是他「始發永安（今北京），過居庸，歷武川（今河北宣德），出雲中（今山西大同西）之右，抵天山（今大青山）之北，涉大磧，逾沙漠。未決十旬，已達行在。」此番北行，既翻山越嶺又橫渡荒漠，歷時三月餘始抵達目的地，可謂艱苦，但耶律楚材可能當時並不知道這相對於他不久之後的遠行來說，不過是小小的短足而已。在綠連河畔（即今克魯倫河），耶律楚材被成吉思汗召見並受到賞識，成吉思汗命其「處之左右，以備咨訪」。這之後不久，耶律楚材就趕上了蒙古帝國歷史上的第一次西征。

金廷南遷之後，已無力恢復對黃河以北地區的有效統治，而蒙古軍隊對所佔州縣又多在殺掠後放棄，因此地方上的地主豪強紛紛起而割據自保，一時間「河北群雄如牛毛」。元太祖十二年（1217年），成吉思汗封拜其「四傑」之一木華黎為太師、國王、都行省，全權負責對金戰事。此後不久成吉思汗統蒙古軍主力西征花剌子模，留給木華黎的蒙古軍只有大約13000人，另有汪古騎兵萬人。木華黎逐漸改變了過去肆行殺戮、得地不守的做法，大力招降並利用漢、契丹、女真等族地主武裝與金朝作戰，而金朝也以高爵招徠華北土豪，分別依附蒙、金兩方的地方勢力彼此展開了拉鋸式的爭奪。此後十餘年間戰鬥雖有反覆，不過總的趨勢是附蒙一方漸居上風，越來越多的地方軍閥倒向蒙古。在山東，儘管南宋也加入了對當地勢力的爭取，但該地最終仍然落入蒙古的控制。蒙古對率部或納土歸降的軍閥、官僚，通常沿用金朝官稱，授予元帥、行省之類統軍管民之職，許其世襲，並可自關僚屬，稱為「世侯」。當時力量較強的世侯，河北地區主要有永清史天澤、易州（今河北易縣）張柔，山東地區則有東平嚴實、濟南張榮、益都李全等。

降西北諸部與滅西遼

元太祖三年（1208年），成吉思汗派兵前往征討西逃的蔑兒乞部脫黑脫阿、乃蠻部屈出律以及「林木中百姓」，前鋒路遇斡亦剌惕部首領忽都合別乞，不戰而降之，忽都合別乞就充嚮導，涉過冰封的額爾齊斯河，大破蔑兒乞部，脫黑脫阿中矢死，屈出律亡走西遼。忽都合別乞為蒙古軍引路，有斡亦刺惕種的忽都合別乞，比萬乾亦惕種「先來歸附」，忽都合別乞引領蒙古軍，「入至黑失惕地面」，斡亦剌（斡亦刺惕諸部）、不里牙惕（即布里亞特，據蒙文史籍載，布里亞特人自稱斡亦剌惕·布里亞特）分布於貝加爾湖東西，併入蒙古部前，就知道使用馬。巴兒渾（即巴爾忽諸部）、兀兒速惕（該部居住在謙河以北烏斯河流域，命名為鄂倫春）、合不合納思（該部居住在謙河之源）、康合納思（該部屬吉利吉思人中的一部落，居住在貝加爾湖西側的安加拉河）諸種部都投降了。

元太祖十二年（1217年），成吉思汗把南下滅金的任務交給木華黎，親自率兵直指西方。當時蒙古蔑兒乞部落首領脫黑脫阿的兒子忽都和乃蠻部落太陽汗的兒子屈出律敗逃楚河流域，仍在西方活動。忽都結集蔑兒乞殘部，圖謀東山再起。元太祖十二年（1217年）秋，成吉思汗命令速不台率軍征伐忽都，速不台翻越崇山峻岭，到達楚河，與蔑兒乞殘部作戰，殺死忽都，消滅了蔑兒乞的殘餘勢力。屈出律與花剌子模國王勾結，篡奪了西遼政權，推翻了契丹人統治，在新疆喀什噶爾、和田至錫爾河右岸地區建立了勢力範圍。

在大規模的西征之前，蒙古就已經開始向西拓展勢力。攻滅乃蠻、蔑兒乞後，首先收服了畏兀兒。畏兀兒在宋朝時稱高昌回鶻，其地以哈剌火州（即高昌，今新疆吐魯番）和別失八里（亦稱北庭，今新疆吉木薩爾）為中心，首領稱亦都護（源於突厥語，意為「幸福之主」），臣屬於西遼。西遼在畏兀兒設少監之官進行監治，其人仗勢欺凌， 引起畏兀兒人不滿。元太祖四年（1209年），畏兀兒亦都護巴而朮·阿而忒·的斤殺西遼少監，遣使降於蒙古。元太祖六年（1211年），他又親赴蒙古朝見成吉思汗，成吉思汗對其十分優待，以女許嫁，視為第五子，「使與諸皇子約為兄弟，寵異冠於諸國」。此後畏兀兒成為蒙古藩屬，須履行入質、納貢、從征等義務，同時亦都護的傳統稱號依然保存，並對畏兀兒領地和百姓享有世襲統治權。中亞地區還有另外一個依附於西遼的民族哈剌魯，居於巴爾喀什湖東南伊犁河、楚河一帶，是唐時西突厥支裔葛邏祿之後，首領稱阿兒思蘭汗。至此他們也殺掉西遼監護官，向蒙古歸降。這一時期，西遼在西方敗於勢力日漸上升的伊斯蘭教國家花剌子模，東部的畏兀兒、哈剌魯又相繼叛附蒙古，國勢衰頹。被蒙古擊敗的乃蠻王子屈出律逃到西遼，篡奪了帝位。元太祖十三年（1218年），成吉思汗遣哲別率軍征討屈出律，將他捕獲殺死，西遼疆土盡歸蒙古。此前，居於貝加爾湖以西的森林部落禿馬惕部起兵反抗蒙古統治，殺死了成吉思汗的得力大將、「四傑」之一博爾忽，吉利吉思等部也起而響應。成吉思汗派長子朮赤領軍鎮壓，將起事平定。

第一次西征

花剌子模是阿姆河下游的古國，都城玉龍傑赤（今土庫曼斯坦庫尼亞烏爾根奇），十一世紀中葉降服塞爾柱帝國，塞爾柱算端任命突厥族侍臣阿努什的斤為監督。十一世紀末，花剌子模沙（Shah，波斯語「國王」之意）被殺，阿奴思子庫都不丁被任命為花剌子模長官，襲用花剌子模沙的稱號，子孫世襲。宋紹興十一年（1141年），西遼擊敗塞爾柱算端，花剌子模沙又向西遼稱臣納貢。其後利用塞爾柱帝國衰落之機，據有呼羅珊西部；十二世紀末，滅塞爾柱算端，勢力擴展至波斯西部。宋慶元六年（1200年），花剌子模沙摩訶末繼位，又征服了呼羅珊東部的古兒朝。元太祖四年（1209年），殺西遼索貢使臣，併吞了撒麻耳幹地區的西遼屬國西喀喇汗國；次年，在塔拉斯河畔打敗西遼軍。至此，摩訶末成為穆斯林世界最強大的統治者。他自稱算端，用武力迫哈里發正式加封，未成；發兵攻西遼，取其西境錫爾河上游沿岸諸城，並策劃進一步向東擴張。元太祖十年（1215年），他派遣一使團到東方探聽蒙古與金朝的戰爭情況。成吉思汗接見了使者，表示願與花剌子模友好通商，並遣使回訪，同時組織了一支四百多人的商隊前往花剌子模貿易。元太祖十三年（1218年），商隊抵達花剌子模邊城訛答剌（今哈薩克斯坦錫爾河中游東之齊穆耳），該城長官哈只兒只蘭禿貪圖商隊財物，竟誣為間諜，將他們盡加殺害，奪其貨物。一名倖免於難的駱駝夫逃回蒙古報告，成吉思汗憤怒至極，遣三使者問罪，又被摩訶末殺一人，二人剃鬚後驅逐出境。於是，兩國之間的戰爭不可避免了。

元太祖十四年（1219年）夏，成吉思汗統領二十萬大軍越過阿勒台山，在也兒的石河駐夏後，即進入花剌子模國境，分兵四路：命察合台、窩闊台圍攻訛答剌，朮赤率一軍沿錫爾河而下攻取氈的、養吉幹等城，阿剌黑那顏率一軍攻取錫爾河上游忽氈等城及費爾幹納地區，自與拖雷統領中軍徑趨河中。摩訶末聞蒙古軍已過錫爾河，慌忙從新都撒麻耳幹退到阿姆河南岸。元太祖十五年（1220年）二月，成吉思汗攻陷不花剌；元太祖十五年（1220年）三月，進圍撒麻耳幹，攻五日，拔之。遣速不台、哲別等統兵三萬追擊摩訶末。摩訶末在蒙古軍緊緊追逼下輾轉西逃，最後遁入寬田吉思海（裏海）南岸附近一個島上，大約在元太祖十五年十二月十六日（1221年1月11日）病死，傳位於其子札蘭丁。

元太祖十五年（1220年）秋後，成吉思汗命拖雷率領一支精銳部隊渡過阿姆河，攻取呼羅珊地區諸城，到元太祖十六年（1221年）夏，馬魯、你沙不兒、也里等城被相繼攻陷。朮赤、察合台、窩闊台三兄弟被派去攻打玉龍傑赤，經過幾個月的激烈戰鬥，始攻克玉龍傑赤。成吉思汗自統大中軍攻取武耳迷等阿姆河沿岸諸城後，於元太祖十六年（1221年）初渡阿姆河，取巴里黑，進圍塔里寒寨，連攻七個月，拖雷率軍來會，才攻克。此時，花剌子模沙札蘭丁在哥疾寧重新集結了約十萬軍隊，進屯八魯灣川，打敗了失吉忽圖忽率領的三萬蒙古軍，聲勢復振，已被蒙古佔領的一些呼羅珊城市紛紛起義響應，殺死蒙古戍將。成吉思汗會合諸路軍隊，越過大雪山（興都庫什山），進攻札蘭丁，而札蘭丁卻因部下諸將爭權奪利紛紛離散，勢力轉衰，不敢抗擊蒙古軍，退卻到申河（印度河）。元太祖十六年（1221年）十一月，成吉思汗在申河北岸一舉擊潰札蘭丁軍，札蘭丁逃入印度。元太祖十七年（1222年）春、夏，蒙古軍繼續攻略申河一帶地區，鎮壓呼羅珊諸城叛亂。秋末，成吉思汗回師撒麻耳幹，在西域諸城設置了達魯花赤鎮守官；冬，啟程東還，元太祖二十年（1225年）春回到蒙古。

速不台、哲別率領蒙古軍完成了追擊摩訶末的任務後，繼續抄略波斯中西部諸城。元太祖十七年（1222年）春，攻入谷兒只（喬治亞）、失兒灣等地，由打耳班（今喬治亞巴庫西北捷爾本特）越過太和嶺（高加索山），進入阿速（又稱阿蘭，高加索北麓的伊朗語族部落）、欽察（突厥語部落，分布在裏海至黑海之北，東羅馬人稱之為庫蠻，俄羅斯人稱之為波羅維赤）之境，先後將阿速、欽察諸部各個擊破，遂駐冬於欽察之地。欽察首領玉里吉向斡羅思（俄羅斯）伽里赤王密赤思老求援，伽里赤王約集斡羅思諸王公到乞瓦（基輔）會商，決定與欽察人聯合起來抗擊蒙古，遂殺死速不台、哲別派來的議和使者。元太祖十八年（1223年）五月，蒙古軍與斡羅思、欽察聯軍會戰於阿里吉河（今烏克蘭馬里烏波爾市北）之東，斡羅思諸王公互不團結，不能協同作戰，終被蒙古軍一一擊潰。速不台、哲別統兵抄掠斡羅思南部諸地後，東還，經亦的勒河（伏爾加河），又攻掠不里阿耳國，然後由裏海、鹹海之北返回蒙古。

統一北方

滅西夏

元太祖二十年（1225年），成吉思汗結束西征東返後，決定先攻滅西夏，隨後集中力量從黃河上游渡河而南，東向攻伐金朝。元太祖二十一年（1226年），成吉思汗以西夏曾拒絕出兵助戰和不履行交納質子為理由，親率10萬大軍從東、西兩路向西夏發動了強大的鉗形攻勢。西路蒙古軍由大將阿答赤統帥，一路勢如破竹，連取沙州、肅州、甘州、西涼府等西夏重鎮；另一路大軍由成吉思汗親自統帥，自漠北南下，攻破黑水、無剌海等城，並於靈州（今寧夏靈武西南）附近黃河岸邊重創西夏軍主力，西夏天險喪失，夏獻宗李德旺驚悸而卒，夏人立南平王李睍為主。

元太祖二十一年（1226年）秋，蒙古軍取西涼府（今武威）及搠羅、河羅等縣。逐踰沙陀（沙漠）東進，至黃河九渡，取應理（今中衛市）等縣。元太祖二十一年十一月初九日（1226年11月29日），蒙古軍開始圍攻靈州。西夏主李睍以嵬名令公為前鋒，發自中興府，帥五十營救靈州。元太祖二十一年十一月十五日（1226年12月5日），成吉思汗揮兵踐水渡河迎擊。蒙古軍箭無虛發，大破西夏援軍。夏主遁回中興府。成吉思汗曰：「李晛經此敗，不能復振矣。」是役，戰況激烈，蒙古軍死者十之一，西夏兵死者十之三。元太祖二十一年十一月二十六日（1226年12月16日），成吉思汗駐蹕鹽州川（在今鹽池縣境）。

元太祖二十二年（1227年）正月，成吉思汗留一部分軍隊圍攻中興府，自己率師渡黃河而南，進入金朝境內，相繼攻破金朝控制的積石州、臨洮府、洮州、河州及西夏的西寧州，西夏和金朝的勢力由此退出河湟地區。元太祖二十二年（1227年）六月，成吉思汗駐軍甘肅清水（今甘肅清水縣）。元太祖二十二年七月十二日（1227年8月25日），病逝於軍中，遺言：「金精兵在潼關，南據連山，北限大河，難以遽破。若假途於宋，金，宋之世仇也，必許我，則由唐、鄧直搗大梁。金雖撤潼關之兵以自救，然千里赴援，士馬俱疲，吾破之必矣。」年六十六歲，在位二十二年。追謚聖武皇帝，後又加謚法天啟運聖武皇帝，廟號太祖。葬起輦谷。是月，西夏國主李睍因糧盡援絕，瘟疫流行，被迫獻城出降，被蒙古軍所殺，存續近兩個世紀的西夏王國宣告滅亡。

聯宋滅金

元太祖成吉思汗去世後，暫由幼子拖雷監國。元太宗元年八月二十四日（1229年9月13日），成吉思汗第三子窩闊台繼承汗位，史稱元太宗。此後，便集中力量攻打金朝，蒙古軍進入甘肅東部地區。到成吉思汗去世時，蒙古已在對金朝作戰中取得壓倒性優勢，金朝只能固守黃河防線，苟延殘喘。據載成吉思汗臨終曾擬定借道於南宋、迂迴從後方給金朝致命一擊的戰略計畫。元太宗三年（1231年），大蒙古國第二代皇帝窩闊台在官山（今內蒙古卓資北）大會諸王，議定分兵三路伐金。窩闊台自統中路軍由山西正面發起攻擊，鐵木哥斡赤斤統左翼軍由山東進兵，拖雷則統右翼軍從寶雞南下，繞道宋境，包抄金朝後方。這一年冬天，窩闊台攻破河中府（今山西永濟西），渡過黃河。拖雷從大散關入漢中，沿漢水東下，經過長距離的艱苦行軍，自鄧州（今河南鄧縣）繞出金朝背後。

元太宗四年（1232年）春，拖雷趁天降大雪之機，大破金軍主力於釣州（今河南禹縣）南邊的三峰山，北上與窩闊台會師，金朝滅亡的大局已定。大將速不台包圍金南京，金哀宗完顏守緒棄城出逃。元太宗五年正月二十三日（1233年3月5日），金京城西面元帥崔立殺留守完顏奴申等，獻南京降蒙古。金哀宗由歸德（今河南商丘）走蔡州（今河南汝南），蒙古與南宋達成協議，合兵將金哀宗圍困在蔡州城內。元太宗六年正月初十日（1234年2月9日），金哀宗慌忙傳位於元帥完顏承麟，不久，城陷，金哀宗自縊身亡，完顏承麟亦被亂兵誅殺。至此，金朝滅亡，但是在秦、功一帶的金朝勢力依然存在。為此，窩闊台命次子闊端從攻宋前線領兵而西，規復河隴地區。元太宗七年（1235年），當闊端率兵進抵鞏昌城下時，金朝鎮遠軍節都使、鞏昌便宜總帥汪世顯率眾歸附，得到闊端的嘉獎。在汪世顯的帶動下，秦、鞏一帶二十餘州，先後歸附蒙古。至此，金朝在西北的殘餘勢力，幾乎為蒙古軍所消滅。

金朝滅亡後，按照蒙、宋協約，蔡州以南歸宋；蔡州以北歸蒙古。於是，蒙古大軍北還，留速不台鎮守河南。可是南宋淮東制置使趙葵卻建議乘蒙古撤軍之機，出兵收復中原。這一建議得到宋理宗趙昀的允准，命趙葵率軍6萬取汴京，徐敏子西攻洛陽。速不台率軍擊退了宋軍的進攻，使南宋收復三京（汴梁、歸德、洛陽）的舉動遭到失敗。這次交戰，成為蒙古決心討伐南宋的導火線。

成吉思汗之後的擴張

窩闊台攻宋之戰

南宋發動端平入洛之役後，蒙古指責南宋「開釁致兵」，破壞盟約，並積極進行大舉南下攻宋的軍事準備。元太宗七年（1235年）春，窩闊台決策攻宋，蒙古軍三路南下，攻勢十分猛烈。西路軍橫掃東至三峽、西至大渡河之間的大片蜀地，曾一度佔領成都，迫使宋軍退守夔門；中路軍攻佔襄陽要地，兵圍江陵；東路軍在兩淮也前出至舒、廬，「謀搗江面」，引起江南震動。但是，由於各地宋軍的積極抗擊，蒙古軍未能進一步深入。

此次攻宋之戰，蒙古軍之所以未能達到滅宋的預期目的，主要有兩方面的原因：一是戰略指導有誤。同時開闢三大戰區，戰線過長，主攻方向不明，兵力分散，而無法實施各路軍協同作戰。二是蒙古軍深入江淮和巴蜀的河網高山地區，騎兵快速機動的特點難以發揮，而暴露了蒙古軍缺乏水軍的劣勢。如入蜀蒙古軍僅郝和尚拔都選驍勇9人乘輕舟往來於江上，卻無力順流而下，東攻兩湖。中路軍進至枝江，遂「自枝江、宜都競上，伐竹木，毀室廬，斧斤之聲日聞，直欲為渡江計」。然而，臨時造船，難以競渡。不建立一支強有力的水軍，蒙古難以實施滅宋計劃。

儘管如此，蒙古軍仍取得不小戰績。開闢了全面對宋作戰的戰場，摧毀了長江中上游地區的許多城防設施，達到了不佔有境土而破壞其生機的目的，為以後攻宋創造了條件。元太宗十三年十一月初八日（1241年12月11日）遲明，窩闊台病死，蒙古統治集團內部紛爭激烈，幾易其主，因此無暇全力部署攻宋，僅有零散的局部戰爭。直至蒙古內部穩定後，再次發動了對宋的攻勢。

第二次西征

元太宗七年（1235年），窩闊台召集諸王大會，決定征討欽察、斡羅思等國，命各支宗室均以長子統率出征軍，萬戶以下各級那顏也派長子率軍從征。諸王以朮赤子拔都為首，以老將速不台為主帥。元太宗八年（1236年）秋，滅不里阿耳。元太宗九年（1237年）春，滅欽察；秋，進兵斡羅思，攻取也烈贊（梁贊）城。元太宗十年（1238年），分兵四出，連破莫斯科、羅斯托夫等十餘城，合兵圍攻弗拉基米爾大公國首府，陷之。元太宗十一年（1239年），滅高加索山北麓之阿速國，攻入斡羅思南境；遣使至乞瓦（基輔）諭降，被殺。元太宗十二年（1240年），拔都親統大軍圍困乞瓦，四周架炮猛攻。其王米海依畏敵，先已逃入孛烈兒（波蘭），名將德米特爾領導乞瓦軍民進行了英勇抵抗，城破，德米特爾受傷被捕，拔都嘉其忠勇，赦之不殺，但乞瓦軍民則遭到殘酷屠掠。蒙古軍攻陷乞瓦後，繼續西進，攻佔伽里赤，其王逃入馬札兒（匈牙利）。

元太宗十三年（1241年）春，拔都分兵兩路，一路由諸王拜答兒、大將兀良哈台率領，攻孛烈兒；一路由拔都、速不台率領攻入馬札兒。拜答兒一軍破散多米兒城，抵克剌可夫，孛烈兒王棄城遁，蒙古軍焚毀其城，遂入西里西亞境。西里西亞侯集孛烈兒諸軍，與來援之捏迷思（日耳曼）軍聯合抗敵，激戰於里格尼茨，被蒙古軍擊潰。里格尼茨之戰使歐洲諸國十分震驚，感受到蒙古入侵的嚴重威脅。但由於教皇和德意志神聖羅馬帝國皇帝的尖銳矛盾，未採取一致的對策。蒙古軍獲勝後，又攻入莫剌維亞，南下與拔都軍會合。拔都軍在撒岳河（當即《元史》所載郭寧河）畔擊潰馬札兒軍，進拔佩斯城（當即《元史》所載馬茶城），分兵四出抄掠。有一支進至維也納附近的諾依施達。冬，拔都大軍渡過禿納河（多瑙河），攻陷格蘭城。元昭慈皇后元年（1242年）初，遣諸王合丹率一軍追擊馬札兒王貝拉四世。不久，窩闊台死訊傳來，拔都率軍東還，元昭慈皇后二年（1243年）初，到達伏爾加河下游的營地。從此拔都就在這裡立國，建薩萊城（今阿斯特拉罕附近）為國都。統有東起也兒的石河，西至斡羅思的遼闊地域，史稱欽察汗國（因以原欽察部地為中心而得名）。

征服吐蕃

隨著吐蕃國滅，出現了百餘年的分裂混亂，佛教亦一度衰敗，其後再度風行。它分裂成許多宗派，與地方的封建貴族勢力結合。它們中，主要有噶當派、薩迦派、噶舉派、寧瑪派等。由於薩迦派的款氏家族與西夏王室夙有姻親關系，據說成吉思汗在第一次出征西夏，取得了青海柴達木地區之後，即致書薩迦寺的大喇嘛，表明了對喇嘛教的尊重和遣軍入藏的意向。但是由於夏、金未滅，成吉思汗未遑遠略，以後又因迭次西征，征服西藏的問題一直未提上日程。然一些鄰近陝蜀的吐蕃首領，已陸續有一部份臣服。

元太宗十一年（1239年），窩闊台的兒子、受封領有青藏地區、駐戍涼州的闊端派將軍多達那波率軍入藏，直至拉薩北部的熱振寺、傑堆寺等地，隨即北撤，向闊端報告烏思藏各派的情況，說：「現在衛藏地方的噶當教派的寺廟最多；達壟教派（即達壟噶舉）的僧人戒律清整；止貢教派（即止貢噶舉）的京俄大師具大法力；薩迦派的班智達學富五明。」建議任命宗教首領來管理其地。元昭慈皇后三年（1244年），薩班（即薩迦班智達，Sa-skya-pandita的簡稱，panditax·為通明「五明」的人）奉召攜其二侄八思巴、恰那前赴涼州；元定宗二年（1247年），與闊端商妥了烏思藏歸順蒙古的條件，並發回了有名的、致烏思藏納里的僧俗首領的信。從此西藏正式歸屬蒙古帝國。

貴由與兩皇后稱制

元太宗十三年（1241年），窩闊台死，忽里勒台會議仍未馬上召開，由窩闊台的皇后乃馬真氏脫列哥那臨朝稱制。脫列哥那狡黠多權術，以濫行賞賜換取宗王大臣擁護，攝政達五年之久。成吉思汗幼弟鐵木哥斡赤斤企圖乘虛而入奪取汗位，但未能成功。元定宗元年（1246年），舉行忽里勒台選汗大會，雖然窩闊台生前曾指定其孫失烈門（窩闊台第三子闊出之子）為繼承人，但脫列哥那卻希望選立自己所生長子貴由。經她的活動，貴由遂被推舉為大汗。

貴由即位以後面臨的首要問題就是整頓朝政，鞏固和加強自己的最高統治地位。脫列哥那稱制期間，貶抑窩闊台時期的舊臣耶律楚材、鎮海和牙老瓦赤等人，使耶律楚材「憤恨而死」，鎮海、牙老瓦赤等人則逃亡，投靠了闊端和拔都。朝政由脫列哥那寵信的法提瑪和奧都合剌蠻把持。汗位虛懸，加上「庶政多親」，宗王貴族們便濫發牌符，遣使馳驛各地，隨意征財索物，汗廷和各地的正常統治秩序都受到嚴重影響。脫列哥那把貴由推上汗位，但仍然掌握著汗廷大權。貴由即位以後，處死了法提瑪，重新起用鎮海、牙老瓦赤等人，並當眾查收了宗王貴族們擅自發放的令旨牌符。貴由不顧脫列哥那的極力庇護，強行擒殺法提瑪，說明他從母親手中奪回了最高權力。母子反目，使脫列哥那不久就死去了。對公然想用武力奪取汗位的鐵木哥斡赤斤，貴由借宗王法庭之手將他處死。

貴由與朮赤之子拔都一向不和，在貴由西征時曾互相辱罵，一直爭執到窩闊台處。等到貴由正式即位，即派親信野里知吉帶出鎮波斯，圖謀對付駐守欽察草原的拔都。元定宗三年（1248年）三月，貴由親率軍隊西行，拔都亦嚴兵為備，但貴由在路上突然死去，醞釀中的內戰終未爆發。皇后海迷失稱制。元憲宗元年六月十一日（1251年7月1日），蒙古貴族立拖雷長子蒙哥為大汗，這就是元憲宗。自此，蒙古帝位復歸於拖雷一系。蒙哥汗命其弟忽必烈總掌富庶的漠南之地，又遷徙窩闊台汗子孫及諸王於邊地，將海迷失皇后賜死，從而鞏固了汗位。

蒙哥攻宋之戰

對於南方，與南宋間戰事也自元憲宗時代而加劇。金朝的討滅，名義上軍事同盟協力者南宋，實質無大助力，因而僅分得陳州（今河南省淮陽）與蔡州東南之地。南宋卻趁蒙古大軍北撤的河南空虛時刻，作軍事上投機，襲入汴京又圖進取洛陽，聞蒙古軍重返才急遽退歸，元太宗遣使責宋違約，戰釁開啟。但交戰只在南宋域內四川以至江淮間進退，大體呈現膠著，以後數年，戰爭性質且轉變蒙古軍的劫掠式蹂躪，攻略城市得手，殺俘居民與掠奪戰利品便退卻。

元憲宗即位六年，授權其弟忽必烈統轄漠南漢地軍、民、政三權，前代以來停滯的南宋領土侵略開始惡化，另一弟旭烈兀出征哈里發政權上一年的元憲宗二年（1252年），南宋經略的準備工作先已著手，忽必烈受命截切南宋四川西部之地南下，平定唐朝南詔國後身的雲南大理國，以及招降吐蕃成功。元憲宗七年（1257年），忽必烈奉召返蒙古本土，副統帥兀良哈台（速不台之子）續又進出中南半島，翌年征服交趾地方南宋屬國，替代李氏大越未久的陳氏安南國，從南宋北、西、南三方面大包圍作戰部署完成。

惟其如此，元憲宗八年（1258年），計劃下本格化南宋征服戰展開，元憲宗末弟阿里不哥留守和林，軍分三道，合四萬人號稱十萬。左翼軍忽必烈自河南南下，以長江中流域的鄂州（武昌）為攻略目標；右翼軍兀良哈台由交趾北上，向湖廣方面會合；元憲宗親自率的中軍，以甘肅省六盤山（成吉思汗崩駕所在）為前進基地，指向四川合州（重慶市以北四川省合川縣），準備奪取長江流域之地而沿江東進。不幸，元憲宗九年（1259年）夏秋之間，蒙古軍抵達四川時軍中痢疫大流行，元憲宗也被傳染不治，崩於合州前線釣魚山營中，年五十二歲，在位九年。南伐諸軍，乃全面北撤，也因猝然發生的元憲宗崩駕大變故，汗位爭奪再昇高層次，爆發同係拖雷位下的親兄弟鬩牆。

降服高麗

蒙古南下征服中國，為避免背後受敵，降服高麗成為必要戰略。從元太宗三年（1231年）至元憲宗九年（1259年），約三十年間蒙古六次出兵高麗。時高麗由武人崔氏主政，元太宗四年（1232年）將國都由開京遷至江華島作長期抗戰。元憲宗七年（1257年），以崔氏政權沒落為轉機，高麗放棄抗戰方針，高麗高宗以還舊都和遣太子入朝為條件請和。元憲宗九年（1259年）四月，太子王倎入朝，但高麗高宗尚未還都開京，元憲宗九年（1259年）六月即病死，元憲宗蒙哥汗則於元憲宗九年（1259年）七月圍攻四川合川城時病歿。元憲宗九年（1259年）閏十一月，忽必烈由襄陽班師北上，王倎奉幣迎謁於道。忽必烈驚喜曰：「高麗萬里之國，自唐太宗親征而不能服，今其世子自來歸我，此天意也。」乃命達魯花赤、束里大等，護送王倎歸國。

王倎於中統元年（1260年）四月即位，是為高麗元宗。時，江淮宣撫使趙良弼上言曰：「高麗雖名小國，依阻山海，國家用兵二十餘年尚未臣附。前歲太子倎來朝，適鑾輿西征，留滯者二年矣。供張踈薄，無以懷輯其心，一旦得歸將不復來。宜厚其館穀，待以藩王之禮。今聞其父已死，誠能立倎為王，遣送還國，必感恩戴德，願修臣職。是不勞一卒，而得一國也。」即建議「宜厚其館穀，待以藩王之禮」、「立倎為王，遣送還國」。陝西宣撫使廉希憲亦有類似之言。此為元世祖放棄對高麗長年用兵，改採懷柔之策的重要建言。

至元元年（1264年），蒙古遣使高麗，詔曰：「朝覲諸侯之大典也。朕纘承丕緒于今五年，第以兵興有所不暇。近西北諸王率眾欵附，擬今歲朝王公郡牧於上都。卿宜乘馹而來庸修世見之禮，尚無濡滯。」高麗元宗因之入覲，至元元年（1264年）十二月回國後，至元二年（1265年）正月遣廣平公王恂、大將軍金方慶、中書舍人張鎰等至蒙古「謝恩獻方物」。至元二年（1265年）五月，王恂等歸國，「帝厚慰遣之，中外稱慶」兩國關係漸親善。

第三次西征

成吉思汗西征時，並沒有徵服花剌子模沙札蘭丁。因此，在他返回蒙古時留下綽兒馬罕繼續追擊札蘭丁。元太宗三年七月十六日（1231年8月15日），札蘭丁敗亡。後來綽兒馬罕和拜住繼續率領蒙古軍隊在西亞和波斯用兵20年，卻並沒有全部征服這些地區。元憲宗二年（1252年）正月，蒙哥決定派其弟旭烈兀發動一次新的西征，以乃蠻人怯的不花為前鋒。這次西征除了動用諸王的士兵外，還抽調了一千多名中國的工匠從征，其中包括著名的火器專家郭侃。

元憲宗六年（1256年），旭烈兀進兵木剌夷國。木剌夷地處裏海之南，十一世紀末建國。蒙古軍入境後攻陷許多城堡，國主兀魯兀投降，木剌夷人民遭到殘酷屠殺。元憲宗七年（1257年），蒙古軍隊開始進攻報達（今伊拉克巴格達）。報達是黑衣大食阿拔斯王朝首都。黑衣大食建國已五百年，一度雖為塞爾柱突厥人佔領，但名義上仍為阿拔斯王朝哈里發統治。蒙古入侵時，哈里發穆斯台綏木是一個怯懦無能、只知享樂的統治者。旭烈兀致書哈里發，要他投降。哈里發自認為是「回教國的共主」，回書拒絕，但又不認真備戰。元憲宗八年（1258年）初，旭烈兀用火炮攻陷報達，哈里發投降，被殺。蒙古軍隊入城後劫掠七天，居民被屠殺的有數十萬人之多，阿拔斯王朝的藝術珍品和華麗的建築物遭焚毀，這座著名的古城被徹底破壞。旭烈兀繼續率軍西進，蹂躪了美索不達米亞，侵入敘利亞，逼近埃及。中統元年（1260年），蒙古軍攻陷阿勒坡和大馬士革，但埃及馬穆魯克蘇丹的軍隊在大馬士革以南阿音札魯特地方大敗蒙古軍，阻止了蒙古向埃及和非洲的擴張。

中統元年（1260年），忽必烈即大汗位，封旭烈兀於波斯，旭烈兀在自己的封地內建立了伊兒汗國。伊兒汗國東起阿姆河，西迄小亞細亞，北接欽察汗國，南至印度洋，都城在帖必力思，報達是陪都。除了上述欽察、伊兒兩個汗國外，窩闊台後裔的封地是以塔爾巴哈臺為中心的阿爾泰山地區，稱窩闊台汗國，察合台後裔的封地是包括阿姆河以東的中亞細亞、謝米列契和今天的新疆天山南北，稱察合台汗國。四大汗國名義上是元朝皇帝的藩屬，而欽察汗國和伊兒汗國實際上變成了獨立國家。

帝國分裂

蒙古的大汗，是各部族的共主，要由各部族公推，鐵木真的稱成吉思汗，便是各部族共上的尊號。其後，窩闊台之立，雖未經部族公推，但因有成吉思汗的遺命，部眾始無異議。到元定宗貴由繼位，已有爭端。元定宗歿後，元太宗及拖雷後人，各欲爭位，元憲宗（蒙哥汗，拖雷之子）因拔都及兀良哈台的援助，始得嗣位。元憲宗嗣位後，分遣宗室諸王於邊遠地區，而以其弟忽必烈領治漢地民戶，因此，元太宗子孫與拖雷子孫，遂生仇恨。窩闊台第七子名合失，嗜酒早卒。合失之子海都，封地在葉密立河（今新疆塔城南之額敏河）之海押立（現巴爾喀什湖東卡帕爾城附近）附近，地處金山（即阿爾泰山）之陽，天山之陰。海都自以為元太宗嫡孫，依前命言，元室帝位當屬於己，無人可以奪取，但卻被蒙哥剝奪，因而一直心懷不滿。

元憲宗七年（1257年），蒙古兵分道伐宋。元憲宗入蜀。忽必烈攻鄂。元憲宗九年七月二十一日（1259年8月11日），元憲宗在釣魚山（今四川合川縣）暴死。元憲宗九年九月初一日（1259年9月19日），忽必烈聞訊元憲宗去世，對侍臣說：「我奉命南來，哪能無功而還！」渡江圍困鄂州（湖北武昌）。元憲宗九年（1259年）十一月，忽必烈得訊，其弟阿里不哥密謀繼位。忽必烈召群臣商議。謀士郝經力主和守議和，迎元憲宗靈樞，收皇帝印寶，北上爭位。正好這時宋丞相賈似道等派密使北上，願意以長江為界，每年貢銀、銅各20萬。忽必烈許可，引軍北還。中統元年（1260年）三月，忽必烈統兵到達開平（今內蒙古多倫縣北）。諸王和左右侍從勸忽必烈在開平即皇帝位，不要前往和林召開忽里勒台（即蒙古選汗大會）。忽必烈同意，宣布即大汗位，這年45歲。阿里不哥不服，也宣布為大汗，調兵遣將。海都也不服，依附阿里不哥。忽必烈平定關成後，親自統兵討伐阿里不哥。中統二年（1261年）十一月，兩軍在和林南南戈壁大戰，阿里不哥敗北。江淮大都督李璮叛亂，忽必烈統兵討伐，一舉平定。中統五年八月十四日（1264年9月5日），定都於燕（今北京），改稱中都。

中統元年（1260年）四月，阿里不哥得知忽必烈先發制人，搶先宣布繼承汗位，於是便在和林召集另一個忽里勒台，在另外一些支持他的諸王的擁戴下，也宣布繼汗位。這樣，一場汗位爭奪的鬥爭，便在忽必烈與阿里不哥兄弟二人之間展開，為此爆發了長達四年之久的戰爭。中統五年七月二十八日（1264年8月21日），走投無路的阿里不哥率領支持他的諸王玉龍答失、阿速帶、昔里吉與大臣不魯花、忽察、禿滿、阿里察、脫忽思等到開平，向忽必烈投降。忽必烈與阿里不哥爭奪汗位的戰爭，由於忽必烈依靠中原漢地人力、物力的支持，最後取得了勝利。它在實質上，是主張「附會漢法」的蒙古貴族對守舊派的勝利。忽必烈獲勝的結果，使漠北與中原地區歸於統一，從而奠定了忽必烈統一全國的基礎。

至元元年（1264年），忽必烈接受阿里不哥歸降時，曾鄭重地遣使通告欽察汗別兒哥、伊兒汗旭烈兀、察合台汗阿魯忽等宗王，邀請他們按照蒙古傳統慣例，一同東來參加正式的忽里勒台選汗大會。但三汗很快相繼去世，他們的繼承人各主一方，對於共同選舉蒙古汗一事不感興趣，卻糾纏於彼此之間的領土爭端，大動幹戈，形同敵國。正在崛起當中的海都，也一再拒絕忽必烈召其入翼的要求。這次忽里勒台會議的流產充分表明，過去那個統一的大蒙古國已經不復存在了。代之出現的，除了忽必烈以漢地為中心建立的元王朝外，就是各自獨立發展的欽察、伊兒、察合台、窩闊台四大汗國。當然，在以後大部分時間裡，忽必烈及其子孫然被尊為成吉思汗的正統繼承人、「一切蒙古君主之主君」，元王朝也在名義上被視為各汗國的宗主國。元代史料經常籠統地稱四大汗國的統治者為「西北諸王」，把他們置於「宗藩」的地位。

大元大蒙古國

建立元朝

忽必烈於中統元年三月二十四日（1260年5月5日）即皇帝位於開平，並以「中統」為年號。「中統」意為「中華正統」，即忽必烈以中原正統標榜自己的新建王朝。在與阿里不哥的較量中，開平起到極為重要的基地作用，忽必烈自己也常駐開平，處理政務。但開平一直以來有都城之實而無都城之名。為了確保開平汗廷的統治地位，同時向全民灌輸一種新的意識，中統四年五月初九日（1263年6月16日），忽必烈將擴建改造後的開平，正式加號為上都。從而不論是在人們的意識當中，還是實際上，上都成為了當時蒙古草原政治權力的中心。新建的帝國雖然開宗明義宣布「祖述變通」，但直至十年後，仍沿用原國號「Yeke mongyol Ulus」，即「大蒙古國」。這一點對雄心勃勃致力於改革的忽必烈而言，不無遺憾。如同王惲《建國號事狀》所言：「伏見自古有天下之君，莫不首建國號，以明肇基之始。方今元雖紀而號未立，蓋未有舉行之者，是大闕然。」忽必烈只因考慮到蒙古貴族的認同程度，將「變通」的步伐邁得慢而穩。經過十年的經營，忽必烈意識到自己的地位已經逐漸穩固，便加快了變革的步伐。建國號、定都邑、立朝儀等一系列工作隨之展開。

中統五年（1264年），改年號為「至元」。至元八年十一月十五日（1271年12月18日），漢臣王惲請建國號，漢臣劉秉忠取《易經》「乾元」之義，奏號大元，漢化女真人徒單公履受命擬詔，於是乃有新的漢式國號「大元」。元的國號，「大元」是全稱，「元」是簡稱，而蒙古語中將「大元」復加於原國號前，並稱「Daion Yeke mongyol Ulus」，即「大元大蒙古國」。國號的變更正是體現了忽必烈「祖述變通」的思想。既要藉助漢法，致力於「天下一家」和大一統的目標，還要繼承祖宗偉業，弘揚蒙古傳統，保持蒙古人的本色，堅守蒙古人的價值觀。從而建立一個蒙、漢二元的政治文化秩序。

統一中國

忽必烈建國號大元，明確表示他所統治的國家已經不只屬於蒙古一個民族，而是中國歷代封建王朝的繼續。至元九年二月初三日（1272年3月4日），忽必烈採納劉秉忠遷都的建議，改中都為大都，正式定其為元朝首都。忽必烈於至元十一年正月初一日（1274年2月9日）在大都正殿接受文武百官的朝賀，大都從此成為元朝的政治中心。元朝建立後，元世祖繼續進攻南宋，主力集中在襄陽、樊城一線。南宋軍民在襄陽、樊城堅守了6年之久。元軍攻佔襄、樊後，分水陸兩路大舉東下，於至元十三年正月十八日（1276年2月4日）攻佔臨安。南宋大臣文天祥、張世傑、陸秀夫在福州擁立益王趙昰繼續抗元。趙昰死後，又擁立廣王趙昺為帝，最後退到南海崖山建立流亡政權。至元十六年二月初六日（1279年3月19日），元將張弘範進攻崖山，宋軍大敗，陸秀夫負帝投海而死，南宋滅亡。至此，元朝統一了全國。

成吉思汗的先祖以一束箭不易折斷的道理，來教導兒子團結的重要性，可是成吉思汗的後代為了權力和利益，卻引起了蒙古帝國分裂的危機。成吉思汗死後，他的兒子和孫兒繼續開拓蒙古帝國的版圖，並相繼成立自己的汗國，這些汗國都是蒙古帝國的一部分。後來，忽必烈與阿里不哥為了爭奪汗位而開戰，內戰維持了四年，最後忽必烈勝出，成為了蒙古帝國的大汗，並建立元朝。可是，忽必烈一直主張漢化，引起了蒙古各派的不滿，窩闊台汗國和察合台汗國都反對忽必烈，漸漸成為獨立的汗國，而欽察汗國早在蒙哥在位時已得到獨立，四大汗國之中只有伊兒汗國承認忽必烈為大汗。此後四大汗國一直各自為政，甚至互相攻伐。直至忽必烈的孫子元成宗繼位，蒙古各派意識到彼此之間的鬥爭是破壞祖先留下來的基業，於是四大汗國與元朝達成和議，重新承認元朝的宗主地位，開設驛路，關塞恢復往來，蒙古皇室內部的紛爭遂告結束。

帝位爭奪

元憲宗死後，元世祖忽必烈更打破公推的慣例，自立於開平。元世祖季弟阿里不哥不服，自即汗位於和林，元世祖自將兵擊降。繼而元太宗孫海都叛變，元師討之，雖獲克捷，但因其地險遠，終元世祖之世，未能將他平定。元世祖鑒於以前汗位繼承的紛爭，乃仿效漢制，定傳子之局。然元世祖以後皇位繼承的鬥爭，仍不因傳子之局而稍減。

至元三十一年正月二十二日（1294年2月18日），元世祖死，太子真金已先死，故諸王中覬覦帝位者，頗不乏人。重臣伯顏，奉元世祖遺命，立真金第三子鐵穆耳，是為元成宗，諸王始無異議。元成宗在位十三年而死，太子德壽先卒，左丞相阿忽臺等謀奉皇后臨朝聽政，而以宗室阿難答為帝。元成宗之侄愛育黎拔力八達與右丞相哈剌哈孫遣使迎其兄海山於漠北，並殺阿忽臺等。海山至大都（北平市），殺皇后及阿難答與諸王，然後即位，是為元武宗，而立其弟為太子。元武宗在位四年死，其弟愛育黎拔力八達繼位，是為元仁宗。元仁宗本有傳位元武宗子和世㻋之承諾，因奸相鐵木迭兒進言，乃有傳子之意，因於延祐二年（1315年），出和世㻋鎮雲南。元武宗舊臣皆感憤怒，遂於延祐三年（1316年）十月奉和世㻋謀叛，事敗走漠北，依察合台汗國，元仁宗乃立皇子碩德八剌為太子。延祐七年（1320年），元仁宗死，太子即位，是為元英宗。

元英宗推行新政，引起蒙古、色目貴族中保守派的不滿。至治三年八月初四日（1323年9月4日），元英宗自上都南還大都，途中駐蹕於南坡。御史大夫鐵失、知樞密院事也先鐵木兒等趁元英宗熟睡之機，以阿速衛兵為外應，發動政變，刺殺元英宗和拜住，此即「南坡之變」。也孫鐵木兒即帝位於龍居河，詔改次年（1324年）為泰定元年（史稱他為泰定帝）。致和元年（1328年），泰定帝病死。其子阿剌吉八即位於上都，改元天順，史稱天順帝。同時，留守大都的燕鐵木兒發動政變，立元武宗之子圖帖睦爾為帝，改元天曆，是為元文宗。之後，兩都之爭由此展開。天順元年十月十三日（1328年11月14日），上都陷落，元天順帝失蹤。天曆二年正月二十八日（1329年2月27日），和世㻋即位於和林，是為元明宗。天曆二年八月初六日（1329年8月30日），元明宗暴斃於王忽察都之地（被元文宗和燕鐵木兒毒死）。天曆二年八月十五日（1329年9月8日），元文宗再即帝位。之後，他又做了近4年皇帝，於至順三年八月十二日（1332年9月2日）病逝於上都，因其後悔毒死元明宗，遺詔傳位於元明宗之子。至順三年十月初四日（1332年10月23日），年僅7歲的元明宗次子懿璘質班即帝位，是為元寧宗，但在位43天就去世，是元朝諸帝中最為短命的皇帝。這樣，在10年中（1323年～1332年），元朝前後更換了5個皇帝。元寧宗死後，元王朝開始步入其統治的晚期。

元末失國

至順三年（1332年），元文宗、元寧宗相繼去世。燕帖木兒請立元文宗子燕帖古思。元文宗皇后卜答失里欲立妥懽帖睦爾，遂遣使靜江迎回。然為權相燕帖木兒所疑問，遷延數月不得立。決策國事皆由燕帖木兒及元文宗皇后，至燕帖木兒死。至順四年六月初八日（1333年7月19日），妥懽貼睦爾即皇帝位於上都（今內蒙古正藍旗東）。改元元統。即位後，清除燕帖木兒勢力。以伯顏為右丞相，獨擅相權，把持朝政，肆行貪暴，天下貢賦多入伯顏家。又仇視漢人，排斥儒士。至元元年（1335年），停止科舉取士，大量起用蒙古、色目人為官，又擅貶宗王，引起朝野不滿。至元六年（1340年）二月，妥歡貼睦爾支持脫脫逐走伯顏，以脫脫為右丞相。脫脫執政，改變排漢政策，恢復科舉制，提倡文治和經史，史稱「脫脫更化」。但因朝政積弊過深，連年水旱災荒，使國庫空虛。以致濫印190萬錠，至元鈔10萬錠，使鈔法敗壞，物價上漲，社會矛盾激化，各地起義不斷。至正二年（1342年）始，黃河泛濫，沿河州郡災荒連年。至正十一年四月初四日（1351年4月29日），以工部尚書賈魯發河北、河南、山東等地15萬民工治河，導致各地農民大起義。

14世紀中葉，在元朝統治下的中國開始了反抗蒙古人統治的鬥爭。至正八年（1348年），鹽商方國珍首先掀起了反抗，接著由宗教秘密結社的白蓮教徒組織的紅巾之亂在各地興起。由此引起了元朝政權的衰落。至正二十八年（1368年），紅巾軍餘黨朱元璋登大明皇帝位，攻擊元大都，元順帝妥懽貼睦爾逃往開平府，後退至內蒙古的應昌府。至正三十年（1370年），明軍追擊至應昌府，元順帝病死，皇太子愛猷識理達臘勉強脫走後繼帝位，這就是元昭宗。此後，元昭宗以喀喇和林為根據地，對明朝進行防禦。這時，元朝殘餘勢力依舊強大。宣光二年（1372年），明軍15萬人分三路進入漠北蒙古高原，在土拉河方面遭到元軍迎擊，數萬人戰死後退卻。宣光八年（1378年），元昭宗愛猷識理達臘死去，繼承他的是被認為是其弟的天元帝脫古思帖木兒。天元九年（1387年），明軍進入東北地區，木華黎國王的後人納哈出率領的20餘萬元軍降於明軍。為了挽救由此產生的東部戰線的危機，脫古思帖木兒親自前往捕魚兒海湖畔，打算與高麗取得聯繫夾擊明軍。然而在天元十年（1388年）卻遭到明軍奇襲而大敗，在數十騎的陪伴下，向喀喇和林落荒而逃。途中，在土拉河畔被阿里不哥後人也速迭兒的軍隊殺死。也速迭兒殺死北元皇帝，廢棄大元國號，自立為汗，稱蒙古可汗，明人稱韃靼可汗。

至於蒙古帝國的四大汗國則在十四世紀面臨著截然不同的命運：國祚最短的窩闊台汗國於至大二年（1309年）被元朝和察合台汗國瓜分而滅亡；位於西亞的伊兒汗國第九任君主不賽因（1304年—1335年）年僅十二歲便繼承汗位，在位雖不到二十年，卻堪稱伊兒汗國的黃金時代。由於他英年早逝，未留下子嗣，在元統三年（1335年）駕崩後，伊兒汗國便因內部長期的王位爭奪戰爭而陷於分裂局面，最後走向滅亡一途。擁有蒙古帝國西部和北部疆土的欽察汗國是蒙古四大汗國中，維持得最久的一個。直到十五世紀，它才因為俄羅斯沙皇國、波蘭王國和立陶宛大公國的壯大而瓦解。從欽察汗國分裂出來的國家當中，以克里米亞汗國的國祚最長，遲至清乾隆四十八年（1783年）才被俄羅斯帝國女皇凱薩琳大帝消滅。位於中亞的察合台汗國則在至元四年（1338年），因為內部對於該如何在伊斯蘭化和成吉思汗所留下的傳統之間折中取捨的問題爭執不休，最後分崩離析。後來帖木兒（1336年—1405年）以武力接收了察合台汗國的領土，他學習成吉思汗出征四方，並且在十四世紀末葉創立了帖木兒帝國。只不過這個帝國也沒有維持多久。

疆域

美國人斯塔夫里阿塔斯在《全球通史—1500年以前的世界》一書中講：「由於蒙古帝國的興起，陸上貿易發生了一場大變革。歷史上第一次，也是唯一的一次，一個政權橫跨歐亞大陸，即：從波羅的海到太平洋，從西伯利亞到波斯灣。14世紀中葉，義大利一本小冊子通過描寫一條起自頓河河口的塔那（Tana，今日亞速 Azov）、橫穿中亞的商路，概述了蒙古和平時商業的重大意義。」

行政區劃

蒙古在被征服地區仿效中國的金朝設立行台尚書省。成吉思汗在位期間就設立了燕京等處行尚書省，燕京行省最初的管轄範圍是金國北部故土；成吉思汗去世後，繼承成吉思汗蒙古大汗之位的窩闊台先後消滅了西夏和金國，至此，西夏故土和金國南部故土全部成為了燕京行省的一部分。1251年蒙哥汗在庭州設立了別失八里等處行尚書省；在呼羅珊設立阿母河等處行尚書省。汗廷管轄東至太平洋，南至印度洋，北達欽察草原的大部分地區，其他地區分封給黃金家族的諸王作為兀魯思（含有屬民的封地）。

政治制度

外交

蒙古帝國建立後征伐不斷，與周邊各國也有大量使臣往來，13世紀時有不少歐洲人從西方來到東方，其中最著名的是意大利人馬可·波羅。早于馬可波羅二三十年就已有不少歐洲傳教士曾從西方來到東方，其中有兩位西歐傳教士柏郎嘉賓和魯不魯乞，就曾分別于1246年和1253一1254年來到蒙古地區，並記載了有關蒙古社會各方面情況的行記。

1240年代起，羅馬教皇英諾森四世、法國國王路易九世等便多次派出傳教使團到蒙古地區去了解蒙古的各方面情況，併到蒙古傳教，停止進攻基督教世界，其中最早率領使團前往蒙古地區的是柏郎嘉賓。1245年4月，六十多歲的柏郎嘉賓從法國里昂出發，經過波希米亞、波蘭到達基輔，然後從基輔出發經過欽察草原、南俄羅斯草原，于1246年4月到達伏爾加河畔拔都的營帳里，拔都無法做決定，讓他繼續東行，到哈拉和林去見蒙古帝國的最高統治者。1246年7月，柏郎嘉賓到達即將舉行登位大典的蒙古大汗之位繼承者貴由處。8月他參加了貴由的登位大典。他在貴由的駐地昔刺斡耳朵住了4個月左右。同年11月，他帶著貴由答覆教皇的蒙文詔書及波斯文譯文啟程，沿著原路返回歐洲。1247年秋，柏郎嘉賓回到里昂，將貴由的答覆書交給英諾森四世，並交上這次出使的詳細報告。用拉丁文寫成的報告後來以手抄本形式流傳于世，並以《蒙古史》或《普蘭·迦兒賓行記》的書名留傳至今。

1247年小亞美尼亞的國王海屯一世派了他的兄弟森帕德到蒙古帝國的中心哈拉和林商議結盟。1254年森帕德帶回了邀請海屯國王回訪的消息，當時拔都正駐紮在伏爾加河流域下游，他召集作為蒙古附庸的海屯去朝拜蒙哥大汗。蒙古大汗蒙哥賜予亞美尼亞王海屯一份詔書，不許任何人欺負亞美尼亞人，並授予了亞美尼亞地區教堂的自治權。亞美尼亞人將此次出訪記錄在了《海屯王中亞記行》。

大蒙古國和南宋因為都與金國為敵，曾短暫建立聯盟滅金，然而在端平入洛之後雙方敗盟，郝經等人作為大蒙古國的使者被南宋拘留。

軍事

公元1204年，鐵木真在消滅克烈部王汗之後，利用與乃蠻部決戰前夕的戰鬥間隙，把軍馬集中在合勒合河旁進行整編。鐵木真下令所有軍隊依十進制組成十戶、百戶、千戶，並委派了各級那顏為各級軍事首領一即十戶官、百戶官、千戶官。這就是整編中正式確立的千戶制，成吉思汗將全蒙古百姓劃分為95千戶。它改變了過去部落聯盟的鬆散性，形成了高度集中的軍事組織形式。並採用功臣後代宿衛斡耳朵的方式建立怯薛用以拱衛汗廷。

經濟

蒙古帝國在鼎盛時期統治從東亞到中亞、西亞、東歐的前所未有的巨大帝國。蒙古帝國的建立加速了東西方的文化、技術交流，促進了多民族的文化交流。整個絲綢之路第一次也是唯一一次被只有一個帝國控制，這使得東西方的商貿往來比其他分裂時期要容易得多。

商業

成吉思汗統治後期，他造成一片和平安定的環境，實現繁榮富強，道路安全，騷亂止息：因此，凡有利可圖之地，那怕遠在西極和東鄙，商人都向那裡進發。因為蒙古人沒有定居於任何城鎮，商旅也沒有在他們那裡彙集，所以衣物在他們當中非常缺乏，跟他們做買賣所得到的利益，人所共知。

蒙古人在絲綢之路沿線設立驛站，歐亞大陸統一在一個政權之下便利了商業的發展和商人的活動。交易的主要商品大致可分為三類：一類是高價格低重量、易運輸的貨物，如香料（不僅包括胡椒、生薑和肉桂等香辛料，還包括芳香料、染料和藥物）、絲綢、珍珠、寶石、貴金屬和毛皮等；二類是大宗商品，包括穀物、木材、黑色金屬、蠟、布匹、酒、糖、鹽、魚等；三類是奴隸和牲畜。印度及遠東地區出產胡椒、生薑、藏紅花、絲綢、珍珠、棉花和亞麻等。蒙古帝國時期歐亞貿易的北部路線重新暢通，卡法、塔納成為黑海北部重要的貨物集散地。貿易發展的促使一些商業重鎮的崛起或複興，伊爾汗國首都大不里士就是其中的典型代表。

畜牧業

蒙古草原的自然環境一直是適宜畜牧生產的，除少數地方覆蓋有很稀疏的森林外，其他地區均為盛產野草的天然放牧區。「這裡不適合種植作物，卻適合飼養畜群，即便算不上十分理想，至少也是相當適宜的。」大蒙古國的牧民們牧養牛、馬、羊和駱駝等牲畜，「逐水草放牧」為其主要經濟活動。對於草場的選擇，當時已經有了較清楚了認識，懂得什麼地方更適合放養牲畜。夏天人們遷到氣候涼爽、水草豐美的山地，冬天遷到比較溫暖的草甸。為了保護草場，蒙古人頒布了法令，「禁草生而斸地者，遺火而爇草者，誅其家」。破壞草原、燒荒毀草的人，要被處以誅其家的重刑，懲治相當嚴厲。窩闊台汗當政時期，「在沒有水的地方挖掘出井，使百姓得到水和草」，這在一定程度上改善了畜牧環境、擴大了草場，促進了草原畜牧業的發展。

技術及手工業

當蒙古人攻下一座城市或者王國時，如果他們發現了有技能的人，例如工匠、手藝人或技師等，這些幸運的靈魂就能免遭屠戮，並被送往特定的地點，為蒙古人工作。他們可能會加入蒙古軍中，並成為炮兵或技師，其他工匠則被派去為蒙古宮廷製造物品。其中最著名的可能是金銀匠巴黎人威廉·比希耶（William Buchier），據魯布魯克記載，他曾在哈剌和林設計並製造了著名的銀製酒噴泉。

除了哈剌和林，最著名的地方是鎮海城。鎮海是蒙古朝廷中的一名高官，他於元太祖七年（1212年）在蒙古草原的中西部建造了這座城，起初是作為軍事據點。這座城市逐漸擴張，城中有一座頗具規模的作坊，裡面有漢人工匠，其中很多人在至元二年（1265年）左右被允許回到華北，在大都和上都附近工作。這可能是忽必烈戰勝阿里不哥並拒絕給予海都等人技術資源的一個結果。另一座城市拜八里（意為「富饒之城」）建於色楞格河畔，成為珠寶與金器的設計和製造中心。在蒙古草原上建立這些製造中心是個合乎邏輯的選擇，這也使後勤制度的建立變得必要，以向居民供應食物和工作。當然，這也增加了前往蒙古草原的交通運輸。

而蒙古草原並不是唯一的工業生產地。蒙古人在葉尼塞河上游支流沿岸建立了一座絲織品製造中心。西伯利亞在歷史上並不以產絲聞名，但是這顯示了蒙古人的能力，不僅遷移了工人，也給他們提供原材料，由此控制了奢侈品的生產。這裡和其他一些地方生產的主要產品是蒙古宮廷極為熱衷的織金錦，又稱「納失失」。生產這種織物需要大量的絲和黃金。絲基本上來自中國，而生產中心則設在蒙古草原和西伯利亞，相對靠近蒙古草原西部的阿爾泰山和葉尼塞河流域的金礦。這樣一來，就降低了製造納失失的成本。1盎司黃金能夠變為長80公里的線，纏在一條基線上，則可以產出長1,600公里的線。儘管生產納失失所需的黃金並不多，但是使納失失生產中心靠近更為昂貴的黃金的產地是說得通的。絲也十分昂貴（確實是絲而不是黃金成了元帝國通貨的準備金），但是用駝隊運輸大包的絲顯然比運輸小包的黃金更加容易，因為黃金比絲更容易消失。

當然，要想獲得黃金，除了強力的後盾還需要有技術的勞動力。蒙古在列格尼茨戰勝波蘭和條頓騎士團等勢力的聯軍之後，蒙古諸王不里帶走了所獲的俘虜，其中有數量很大的一隊日耳曼金礦工人。這些戰俘在中亞度過了餘生，在距今塔什幹東北約270公里處的塔剌思附近為不里工作。蒙古通過入侵花剌子模帝國一戰，也獲得了數以千計的技術工匠。儘管不應完全相信拉施德丁的估計，他說蒙古人將10萬名工匠遷往「東方之地」（bilad-i sharqi），但毫無疑問，到來的工匠確實是數以千計的。

農業

在大蒙古國時期，作為遊牧經濟區的蒙古草原很早便發展起了農業生產。蒙古建國前後的不斷征戰，使不少農耕民族的人們成為俘虜被運回草原，特別是蒙古人「掠中國之人為奴婢」，並將他們運回草原，這些漢人因為「必採食而後飽」的飲食習慣，在水源相對充足的地區開闢出小片耕地，草原上出現了農業生產活動。對於這些農事活動，窩闊台是支持的。在和林境內，有個人種植蘿蔔，獲得了一些收成；另有一人在和林附近種植了一些柳樹和杏樹苗，並長出了嫩芽（由於嚴寒，樹在當地很難生長）。因為這些成績，窩闊台對這2個人給予重賞。此後，這種耕作活動不斷得到發展，到元定宗二年（1247年）張德輝應忽必烈徵召北上和林時，和林的居民已「多事耕稼，悉引水灌之，間亦有蔬圃」了。

貨幣制度

大蒙古國根據被征服地區的傳統鑄造了不同種類的金銀幣，並廣泛使用紙鈔作為貨幣。

賦稅與徭役

蒙古大汗窩闊台即位之初，接受建議，初定地稅之法，地稅的稅率「上田畝稅3.5升，中田3升，下田2升，水田5升。」由于蒙古統治者的重視，設立專職官員負責商業稅的徵收。

社會文化

宗教

蒙古族原來信奉薩滿教，這是原始的萬物有靈信仰。除了主要信奉的薩滿教，也有一部分信奉景教（基督教的一支），宗教是他們精神生活的主要內容。成吉思汗建立大蒙古國以後，向外擴張，接觸到佛教、道教、伊斯蘭教、基督教等多種宗教。大蒙古國的諸汗，認識到宗教有利于統治的鞏固，對各種能為自己「告天祝壽」的宗教原則上都是保護和支持的，當然有時也根據需要和愛好而有輕重之分。蒙古統治者對于各種宗教原則上都採取兼收並蓄的態度，多種宗教的興盛，是蒙古前四汗時期文化的一大特色。

思想

原金朝統治下的北方農業地區，當時稱為「漢地」。成吉思汗對金用兵，奪取了包括金中都（今北京）在內的大片土地，金朝被迫遷都南京（今河南開封）。窩闊台汗時期，蒙古滅金，實現了對「漢地」的統治。「漢地」歷來占主導的是以儒學為核心的中原傳統文化。成吉思汗接觸過個別「漢地」士人，如契丹人耶律楚材，以及佛、道二教的代表人物，但中原傳統文化在他的心目中是沒有地位的。窩闊台汗曾接受耶律楚材的建議，採取過一些保護「漢地」文化的措施，如以考試方式確定儒戶、立經籍所、封衍聖公等，但隨著耶律楚材在政治上失勢，這方面的措施沒有再推行下去。此外，窩闊台汗還曾下令在燕京（今北京）興辦學校，培養翻譯人才，此事指定全真派的道士負責。這是蒙古學校教育的濫觴。貴由汗在位時間很短，忙于統治集團內部的爭鬥。繼起的蒙哥汗「自謂遵祖宗之法，不蹈襲他國所為」，「酷信巫覡卜筮之術」，對「漢地」的儒學沒有興趣。他曾問：「儒者何如巫、醫？」實際是認為儒者無用。在蒙古上層，他的這種想法是普遍存在的。「漢地」的道教、佛教，得到蒙古統治者的扶持，聲勢日盛。因為利益衝突，佛、道二教在蒙古統治者主持下舉行兩次辯論，成為當時「漢地」思想文化領域的一件大事。另一方面，「漢地」的漢人世侯，如東平（今山東東平）嚴氏、真定（今河北正定）史氏等，在自己管轄範圍內做過一些招徠儒士文人、整治學校的舉措，對于儒學的延續，起了有益的作用，當然規模是有限的。

文學、史學與語文

蒙古族生活在漠北草原，從事遊牧生活。原來沒有文字，成吉思汗在建國前夕滅乃蠻部，俘獲畏兀兒人塔塔統阿，命他用畏兀兒字母書寫蒙古語，從而創立了回鶻式蒙古文，這是蒙古族文明發展過程中的一件大事。

《蒙古秘史》是用畏兀體蒙文寫成的蒙古第一部史書，它的出現是史學的一件盛事，產生了深遠的影響。伊爾汗國的史學家拉施德丁則根據《金冊》等蒙古宮廷記錄編撰了著名的蒙古史書籍《史集》。

在金朝統治下，士人們熱衷于詩詞歌賦，關心理學者極少。反之，理學在南宋統治地區得到很大發展，朱熹是南方理學的代表人物。窩闊台汗七年（1235）蒙古對南宋用兵，攻陷德安（今湖北德安）等地，大肆俘掠。儒生趙複、硯堅等因此北上，趙複在燕京開辦太極書院，硯堅等在各地教授學生，南方理學得以北傳。許衡、姚樞等人都成了理學信徒，後來相繼入忽必烈幕府。在詩文方面，一批金朝「遺民」的創作，成為文壇的主流。遺民文學的特點，不外是懷念故國，感懷身世，有的還對蒙金戰爭造成的災難進行批判。元好問是他們中最有影響的代表。異軍突起的是新西域詩，耶律楚材和丘處機以詩歌記述他們的西域見聞，為當時的文壇增添了光彩。一種新的藝術形式——雜劇開始成型，在城鄉演出。在史學方面，金史特別是金朝亡國史的編纂成為一時風氣，而多種蒙古和西域行記的出現，應視為這一時期文化的一個特點。

人口

成吉思汗曾夢想「讓青天之下皆成蒙古人之牧場」。很多古代文獻都記載，在蒙古的擴張過程中，無數的古代文明遭到毀滅，無數城市被摧毀，根據R. J. Rummel估計，在蒙古帝國的入侵下有3000萬人被殺。在蒙古帝國對西方的擴張過程中有2,000萬人被屠殺；整個亞洲的人口分布亦發生重大變化。David Nicole 在The Mongol Warlords中說，「恐怖和大規模滅絕反對者是蒙古人屢試不爽的戰術」。伊斯蘭世界的東半部經歷了恐怖的死亡與毀滅。從1219年到1260年，由于大屠殺和饑荒，波斯的總人口從1200萬下降到110萬。在中亞河中地區和大呼羅珊，自希臘—巴克特利亞王國時期建立的水利灌溉系統被徹底毀滅，同時也伴隨著無數良田荒蕪和成為沙漠；在西亞，自阿卡德帝國和古巴比倫時期建立的水利灌溉系統被徹底毀壞，大量良田荒蕪。據統計，西亞地區的耕地面積至今未恢復到蒙古人入侵之前的60%。中亞、西亞及東歐至少七十多個城市遭到蒙古軍屠城，有的城市甚至被多次屠城，給當地人民造成巨大災難和痛苦記憶。歷史學家估計匈牙利王國（1241年—1242年）當時200萬人口中的一半死于蒙古入侵。基輔羅斯幾乎所有的城市均被摧毀，投降者作為奴隸，大部分因繁重的勞役很快死去，戰俘則加入蒙古軍隊繼續西征。其人口同樣有大約一半死于蒙古入侵。此外，Colin McEvedy的《世界人口史地圖集》（1978）估計俄國歐洲部分的人口從入侵前的750萬下降到700萬。中國地區的人口在蒙古入侵的七十年間明顯下降。在蒙古入侵以前（1200年），中國（包括金朝、西夏、南宋、大理國）人口約有1億4千4百萬，甚至更多，而到1278年（1279年完全占領）只有7,000萬人。但學術界今天對此也有不同看法，認為人口數量的劇烈下降同樣有人口統計的不完善和大規模遺漏或者蒙古軍隊帶來的傳染病的原因。

然而蒙元史學家傑克·威澤弗德（Jack Weatherford）指出成吉思汗允許民眾自由地傳播有關他或蒙古人的最壞的和最難以令人置信的傳聞，當時成吉思汗意識到，傳播恐怖的最好方式不是通過士兵的行為，而是通過文人的筆。蒙古人操縱宣傳的機器並且經常誇大戰爭中的死亡人數，意圖散播恐懼。他亦指出：「儘管蒙古軍隊實行的是一種前所未有的殺戮，並幾乎是將死亡當作一種政策，而且可以肯定的是，他們還將死亡當作是製造恐怖的一種思考方式，但他們卻以一種影響重大而又令人吃驚的方式，脫離了那個時代的普通慣例。蒙古人並不實施嚴刑拷打、毀傷肢體或使人殘廢。在那個時代，戰爭通常是以一種恐怖的形態來進行的，而且同時代的其他統治者，通過公開拷打或駭人聽聞的斷肢毀體方式，使用原始而又野蠻的策略，向民眾灌輸恐怖和驚悸……從中國到歐洲，文明世界的統治者和宗教領袖都依憑這些駭人聽聞的手段，通過恐怖來統治自己的民眾，通過驚駭來打擊敵人的信心。」；「與同時代文明軍隊的恐怖行為相比較，蒙古人並不是通過兇猛而又殘忍的行為來引起恐怖的，而是由於他們快速而又有效的征服，以及他們似乎完全輕視富人和有權勢者的生命而引起恐怖。」；「與傳播的恐怖傳聞相比較，起初向蒙古人投降的那些城市，得到了寬大而又仁慈的對待，於是那些城市居民就天真地懷疑起蒙古人的能力。投降之後，很多城市起初都忠順地服從，而一旦蒙古人離開他們的國家，他們就馬上反叛。由於蒙古人僅留下少數幾位官員進行管理，而且又沒有駐紮小部隊留守城市，居民們誤以為蒙古人的撤退是虛弱的表現，並且想當然地以為蒙古主力部隊將再也不會原路返回。對於這些城市，蒙古人是毫不留情的；他們迅速返回叛亂的地方，並徹底地摧毀它們。一個被徹底毀滅的城市是無法再次叛亂的。」

對後世的影響

蒙古帝國和黑死病

通常認為，1346年，在蒙古欽察汗國軍隊進攻黑海港口城市卡法（又譯克法，現烏克蘭城市費奧多西亞）時，用拋石機將患鼠疫而死的人的尸體拋進城內，這是西方社會有紀錄以來第一次細菌戰。鼠疫原產中亞，其攜帶者是土撥鼠。在蒙古帝國之前鼠疫曾多次傳入中國，所以雖然中國也曾發生過地區性鼠疫傳染，但中醫在與鼠疫的反覆鬥爭中逐漸累積起經驗，而歐洲人則在此之前從未接觸過鼠疫。在卡法的一個熱那亞商人將帶病的跳蚤無意間帶到意大利的熱那亞共和國，于是鼠疫在歐洲廣泛傳播，最終在1348年—1349年造成2,000萬人死亡，成為令人聞之色變的「黑死病」，因為鼠疫患者皮下淤血、全身發黑而死。

也有一種說法認為鼠疫是絲綢之路上的商人把病菌帶到中東，然後又傳播到歐洲的。

黑死病使得中世紀的歐洲失去三分之一的人口，而對人關心的人文主義隨之覺醒。歐洲人文主義文學的第一部代表作《十日談》就是喬凡尼·薄伽丘（Giovanni Boccaccio，1313年－1375年）在黑死病最氾濫猖獗的時期寫成的，描述至正八年（1348年）發生在義大利的可怕瘟疫。然而也是在此時，歐洲竟迎來文藝復興的曙光。

對各國的影響

俄羅斯

蒙古人來到俄羅斯前，俄羅斯的中心在基輔（今烏克蘭首都），蒙古人來到俄羅斯後摧毀了基輔，並一手扶植起莫斯科，把莫斯科打造成俄羅斯的政治、軍事和經濟的中心，而現在的俄羅斯，正是莫斯科的延伸。今天，世界上最大的國家俄羅斯的形成有明顯的當年蒙古的因素。1920年代，俄羅斯的歐亞主義就說：「俄羅斯與西方不相干，與斯拉夫（Slavdom）也無關。」瓦西里·奧西波維奇·克柳切夫斯基和他的學生認為俄羅斯的統一，蒙古至少有一半功勞。另一位歐亞主義哲學家尼古拉·特魯別茨柯伊在他的經典著作《論俄羅斯文化中的圖蘭成份》指出「莫斯科要感謝蒙古統治，俄羅斯政府制度也是蒙古式的。從本質上說，俄羅斯是一個東正教蒙古國家。俄羅斯人的日常生活深受蒙古影響，有大量蒙古語借字、郵政、稅收、服飾也受蒙古影響，軍法制度也是從蒙古學的。」

西亞

受到第四代大汗蒙哥命令的旭烈兀，率領軍隊前往征服阿拉伯世界，攻陷並徹底破壞了曾經是世界大都市、領導世界史、為阿拉伯世界中心的巴格達。結果，阿拔斯王朝滅亡，阿拉伯世界的中心轉移到了埃及的開羅。蒙古人以新都大不里士為中心，在西亞建立了伊兒汗國。

歐洲

元太祖十三年（1218年），成吉思汗藉口蒙古商隊在中亞細亞的花剌子模國境被殺掠，率大軍開始西征。成吉思汗西徵令歐洲諸國極為震撼，中國與歐洲諸國也開始普遍接觸。蒙古大軍所進行的大規模的東西兩方戰役，幾乎從印度河一直延伸到第聶伯河。從他進攻中原的第一次戰役開始，到元太祖十八年（1223年），在12年之內，蒙古軍隊曾經到達太平洋、印度河和黑海。在13世紀歐洲受到極大震動，以城堡為中心的歐洲正把基督教世界的邊界向前推進，並與伊斯蘭教為敵。在此階段裡，伊斯蘭教仍然是基督教歐洲畏懼的唯一敵人。蒙古人的突然出現，不僅是一個晴天霹靂。用一位外國史學家的話來說：「由於我們的罪惡，我們不知道的部落來到了，沒有人知道他們是什麼人，他們是從哪裡來的，也不知道他們的語言是什麼，他們是什麼種族，他們信仰的宗教是什麼——只有上帝知道他們是什麼人，知道他們是從哪裡跑出來的。」「韃靼人從第聶伯河折回了，我們不知道他們是從哪裡來的，也不知道他們再一次躲藏在哪裡。由於我們的罪惡，上帝知道，他是從哪裡把他們接來懲罰我們的。」歐洲人對蒙古大軍的恐懼心態可見一斑，這影響到後來包括英國。這後來構成19世紀末20世紀初席捲西方的「黃禍」論的歷史起因之一。如清光緒三十一年二月二十五日（1905年3月30日）出版的《東方雜誌》上有一篇文章就說：「白人所謂黃禍之說，不知其起於何時。說者謂成吉思汗以鐵騎蹂躪歐洲，西歐婦孺亦嘗震驚於黃人之大創，而黃禍之說以起。」

日本

元滅宋時，當時日本正值北條氏控制的鐮倉幕府統治時期。元世祖忽必烈欲收日本為藩屬，於至元三年到至元十年（1266年～1273年）的七年間，先後七次遣使招降日本未果，遂於至元十一年（1274年）、至元十八年（1281年）兩次渡海遠征日本，都以失敗告終。而鎌倉幕府雖然擊敗了蒙古人，但同時也背上了沉重的財政包袱，無力給予各地御家人土地和金錢上的賞賜，幕府與武士之間的關係日漸鬆懈，反抗幕府統治的實力逐漸形成。50年後日野俊基等發動勤王運動，推翻鐮倉幕府。不久足利尊氏崛起，與勤王派為敵，雙方相持不下，歷時50多年，史稱南北朝時期（1336年～1392年）。至足利尊之孫義滿時，南北朝對峙局面始告結束，但武人專政依然如故。足利義滿設幕府於京都室町，稱室町幕府（1336年～1573年）。

在明治維新後，日本國內對蒙古帝國入侵日本的歷史進行了重新評價。在當時尊王攘夷論的史觀下，元征日本失敗不僅被政府支持的神道教渲染為「神風護國」；封建武士在對抗蒙古入侵者時頑強抵抗的表現也被宣傳為武士道的楷模。在此兩點宣傳影響下，使當時不管是政府或是民間都普遍相信日本是受到天照大神庇佑的「神國」，能夠在對抗外國威脅時戰無不勝。而隨著其後日本躍升為亞洲強國，並在其後近百年的各種對外戰爭中屢次獲勝，更加深了日本人對這個神話的迷信，一直至二戰後日本戰敗「神風護國」論才息微。

朝鮮半島

高麗政權持續了約500年，但在末期時國土卻遭到元朝的大軍侵略，不得不成為臣從。高麗也跟著元朝過海攻打日本，即「元寇」事件。當元朝因紅巾之亂而衰退後，高麗便與元朝斷交。廢掉元朝幹預之下所設置的行政機關，並重建高麗時代的各種制度。然而，隨著明朝在中國的崛起，高麗的政權也分成親明派與親元派而混亂不堪，親明派的國王被親元派所暗殺、喪失了統治能力。親明派的高麗武官李成桂眼見情勢不妙，於是當機立斷地發起政變、廢黜親元派的國王。接著，更迫使做為傀儡被拱上王位的國王讓位，建立朝鮮王朝，成為初代國王「朝鮮太祖」。李成桂所成立的朝鮮，被冠上其家族姓氏而稱為「李氏朝鮮」。繼高麗之後，李氏朝鮮也存續了500年。

其他影響

據英國《星期日泰晤士報》2004年6月13日報導，英國牛津大學遺傳科學家布萊恩·賽克斯在當年6月推出了有關男性Y染色體研究的新書《亞當的詛咒》，他在書中聲稱，成吉思汗可能是歷史上最成功的「播種者」。追溯歷史，成吉思汗率領的蒙古騎兵將中國版圖擴張至歷史最大，同時也使其子孫在歐、亞兩洲的土地上繁衍，現在全球至少有1600萬男性，與成吉思汗有血緣關係。英倫三島也可能有他的子孫，其中還包括英國皇室家族。

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