belligerent (adj.)

1570s, "waging war, engaged in hostilities," from Latin belligerantem (nominative belligerans), past participle of belligerare "to wage war," from bellum "war" (see bellicose) + gerere "to bear, to carry" (see gest). The noun meaning "party or nation at war" is from 1811. Related: Belligerently.