Aside from a general troop or company standard, how would individuals on a battlefield identify an enemy combatant from a friendly combatant? Especially for land battles during mid-engagement where formal battle lines would become less distinct. From what I can tell general field attire and armour were fairly similar between European armies during the Medieval time period. The addition of heavy armour and it's limitations on vision would seem to further compound the problem of identifying "who's who" during an engagement. Was there any system in place to assist with this or was their some aspect of uniform that helped with identification?