After watching The King on Netflix and the Battle of Agincourt I was left wondering how did the knights on both sides tell who was who in the heat of battle. I would have thought it would be near impossible as the armor on both sides would look similar but at the same time they would need to be able to tell the difference unless they wanted to attack their own country men.
Sorry if this was asked before
The best answer is clearly the one straight from the horse's mouth. Hearken to the words of His Majesty u/Henry_V_Rex, precisely in response to The King's depiction of Agincourt.
There is also in the VFAQ this post from u/vonstroheims_monocle examining the various means of identification available to Medieval combatants. Though care should be exercised reading the links provided in that thread, all of them being from the dark days of pre-2014.