応おう戦せん

noun, noun or participle which takes 'suru', intransitive verb

fight back; return fire; counter-attack; accept a challenge

Used for military combat, sports, arguments, or any situation where one responds to an attack or challenge. Often implies a defensive-to-offensive shift.

• 敵てきの攻こう撃げきに応おう戦せんした。

  We fought back against the enemy's attack.

• 相あい手てチームの挑ちょう発はつに応おう戦せんして、乱らん闘とうになった。

  They responded to the other team's provocation, and it turned into a brawl.