There is a great video that depicts the actions of both sides in the battle of Agincourt:
Interestingly enough, the reason for the English victory over such great odds, was the English bowmen and the invention of the horse collar.
Farm fields were plowed by using oxen, which worked well but was slow. If you tried to plow with horses, the oxbow that attached to the plow, would hit the horse across the throat and cut off his air. The invention of the horse collar put the weight of the plow across the horses shoulders allowing the English peasants to plow with horses at a much faster rate… giving the average English farm worker something he never had before… Free Time!
The king ordered that all English men had to use this new found free time to become proficient in the use of the long bow. Towns would organize long bow competitions, then competitions against neighboring towns, which added to the interest and skill of the English bowmen.
Those same English bowmen turned the tide of the outnumbered English to victory. (Had the English lost the battle, these posts would probably be written in French, not English!
(1) French had been the official language of England for most of the 350 years before Agincourt, but was being replaced by English, since English had always been the language of the common folk. (Or at least since the Angles, Saxons and Vikings had pushed out the Celtic-speaking British.)
(2) Defeat at Agincourt would have meant that the English kings would have lost their French territory a bit more quickly – not that the French would have invaded England.
When I saw the Branagh version of Henry V I became curious about the date of St. Crispin’s Day. I decided, though, that I wouldn’t look it up, I’d just wait until I stumbled across it somewhere.