noun, noun or participle which takes 'suru'
return fire; shoot back
Military or combat term for firing back at an enemy who has fired first. Often used in the pattern 応射する.
敵の攻撃に対して直ちに応射した。
They immediately returned fire against the enemy attack.
反撃 is a broader counterattack, not limited to shooting. 応射 specifically means returning fire with guns or artillery.
Compound of 応 (respond) and 射 (shoot). The exact historical derivation is uncertain, but the kanji combination transparently conveys 'shoot in response'.