friendly fire

Noun

friendly fire (uncountable)

1. Weapons fire coming unintentionally from allied or friendly forces rather than from enemy forces, usually that which causes damage or casualties.
   • It is clear that the firing of very heavy guns, or the enemy's fire in return, would very seriously interfere with an abbatis, or anything of that kind, and it will be only something of the lightest character, or something that is placed at a considerable distance from the friendly fire, the fire...1867 June 3, A[lexander] Moncrieff, quoting Jasper Selwyn, “[Evening Meeting.] Further Particulars Regarding [Colin Scott-]Moncrieff's Protected Barbette System.”, in Journal of the Royal United...
   • The slaughter of one's own troops by being fired into by their friends in rear. We are very much concerned over the question of avoiding loss from the enemy's bullets while passing through the danger zone, but what have we done to avoid our bravest fellows, the survival of the fittest, those who...1910 May–June, P. E. T., “[Reviews and Exchanges.] The Franco-German War.”, in T[heophilus] F[rancis] Rodenbough, editor, Journal of the Military Service Institution of the United States, volume...

   Synonyms:

   blue-on-blue