Titus Livius (Livy), The History of Rome, Book 44
Alfred C. Schlesinger, Ph.D., Ed.

41. ... led... the battle. The men were stirred by the prestige of his office, the fame of the man, and above all by his age, for though he was over sixty he kept assuming functions of men in their prime in undergoing an outstanding amount of toil and danger. The legion filled the space between the light infantry and the phalanxes and broke the enemy line. [2] In the rear were the light infantry; the consul faced a unit with metal shields —these were called the Bronze Shields. Lucius Albinus the ex-consul was ordered to lead the second legion against the White Shield phalanx¹ ; this was the centre of the hostile line. [3] On the right wing, where the battle had begun near the river, the consul brought up the elephants and the squadrons of the allies; and from this point the flight of the Macedonians first began. [4] For, as frequently men's new inventions appear strong when described, but in actual trial, when there is need for action rather than a description of how they will act, these inventions disappear without achieving any result, so in this battle the anti-elephant corps was [p. 229]a mere name without practical effect.² [5] The charge³ of the elephants was followed up by the allies of the Latin Name, who routed the left wing. [6] In the centre the charge of the second legion scattered the phalanx. No reason for the victory was more obvious than the fact that there were many scattered engagements which first threw into confusion and then disrupted the wavering phalanx. The power of this formation when closed up and bristling with spears extended is irresistible; [7] but if by attacks at several points you compel them to swing their spears about, unwieldy because of their length and weight, they become tangled in a haphazard mass; and if indeed some sort of uproar is heard on a flank or from the rear, [8] they are involved in utter confusion. Such was the case on this occasion, when the phalanx was compelled to meet the Romans who were attacking in groups, while the Macedonian line was broken at many points. The Romans for their part kept infiltrating their units wherever gaps presented themselves. [9] If they had attacked frontally in solid line against an orderly phalanx, as happened to the Paelignians who at the beginning of the battle recklessly met the light infantry, the Romans would have spitted themselves on the spears and would not have withstood the solid line.⁴