Nouns

(n)combatant, battler, belligerent, fighter, scrappersomeone who fights (or is fighting)

Adjectives

(s)aggressive, belligerentcharacteristic of an enemy or one eager to fight“aggressive acts against another country”, “a belligerent tone”
(s)belligerent, militant, war-ridden, warringengaged in war“belligerent (or warring) nations”