A question that has been in the back of my mind for sometime now. Obviously throughout our storied and bloodied history, there have been many instances of confused and drastic hand-to-hand combat between forces similar in uniform (I say uniform here meaning an actual military dress or just basic peasant clothes) and physical appearance.

Factoring into consideration night time battles, smoke, fog, and mud, were there any established methods of discerning friend from foe between individual combatants during a heated melee? Do you know of any battlefield commanders who took this problem into account?

My frame of reference for this question comes from thinking about how Japanese samurai would sometimes fight with the flag of their lord attached to themselves. Whether to show their power or for some other reason, this definitly would have had an effect on reducing friendly fire incidents, blue-on-blue incidents. I wonder if there were ever any sort of concious consideration of this issue on other battle fronts across the globe.