You must be referring to the Battle of Agincourt, as Henry V was heading back to Calais after laying a too-prolonged siege of Harfleur, during the 100 Years War.
If it's Agincourt, then Bret talks about it quite a bit in the article. Essentially, it was the best case scenario for bows and even then both the French infantry and cavalry were able to advance and get to the English lines. However, both were weakened enough that they were defeated by the English forces waiting for them.
