friendly fire 
noun [mass noun] Military
Weapon fire coming from one’s own side that causes accidental injury or death to one’s own forces.Although he was mortally wounded by friendly fire, the flank attack continued under Stuart the next day, joining up with Lee....
- Although the combatant forces are heavily intermixed, friendly fire does not appear to have been an issue during the actual battle.
- And then there is the added danger of mines, hidden weapons, friendly fire and the environment itself.