friendly fire

The firing of a weapon by one's own forces resulting in casualties of an ally or a member of one's own troops. Miscommunication between the two military units meant each was unaware of the other's presence in the area of conflict, resulting in friendly fire that led to the deaths of two soldiers. If that guy keeps treating his men so poorly, he better watch out for friendly fire, that's all I'm saying. By some miracle, there were no casualties in the instance of friendly fire between the two units.