In medieval Europe, how did heavily armored knights know friend from foe in the battlefield in close combat after their armies have clashed?

by diabolic_soup

To me all plate armors look the same. Did each army wear any particular insignia? In the peak of the fight how could they know who to attack?

Goiyon

This question has seen immense interest since the Netflix premiere of The King. Luckily, it has been answered rather extensively by u/Henry_V_Rex himself during the Day of the Dead event and even more recently with a contribution by u/AlviseFalier.