More can always be said on the matter, of course, but as this exact question of combat identification is one of the more common warfare questions on the sub, here's a few previous posts for your perusal:

• u/WARitter goes into the various means of identification combatants had then;
• u/Goiyon looks at the same, and also notes the dimensions of combat then;
• but this, clearly the best answer, is one straight from His Majesty u/Henry_V_Rex.