“The French men-at-arms then hit the English men-at-arms, and had some success, but this is when the English archers counter-charged and absolutely massacred the French men-at-arms.” How do archers counter-charge, they might have some side weapon but they’d be lightly armored and up against enemies in plate?

You jump someone from a direction they’re not expecting, while they’re busy fighting somone else, you knock them down into the mud, step on their chest or back, and then put one of these

through the eyeslits of their helm, or up under their armpits or their groin where there was likely to be only chainmail, or into the join between two plates, over and over again:

This is a kind of stiletto that was called a misericorde, and while the name is meant to signify a merciful killing stroke, they were carried by common soldiers to, in the words of Ambrose Bierce, “remind an unhorsed knight that he was mortal.”