Before military uniforms, how did warriors know which side everybody was on once the two armies met for sword combat? Was it common to accidentally kill somebody from one's own side?

Hello,

Not to dissuade further conversation on this topic, but there are 2 threads on this subject listed in the FAQ for this subreddit:

u/400-Rabbits has an excellent answer here regarding Mesoamerican history and u/vonstroheims_monocle has another answer to this question here.

edit- formatting, always mix up the brackets and parentheses