Friendly Fire

Friendly fire is inadvertent firing towards one's own or otherwise friendly forces while attempting to engage enemy forces, particularly where this results in injury or death. A death resulting from a negligent discharge is not considered friendly fire. Neither is murder, whether premeditated or in the heat of the moment, nor is deliberate firing on one's own troops for disciplinary reasons, as in these cases there is no intent to harm the enemy. Similarly, inadvertent harm to non-combatants or structures, usually referred to as collateral damage, is also not considered to be friendly fire.

The term friendly fire was originally adopted by the United States military. Many North Atlantic Treaty Organization (NATO) militaries refer to these incidents as blue on blue, which derives from military exercises where NATO forces were identified by blue pennants, hence "blue", and units representing Warsaw Pact forces were identified by orange pennants.