WordNet sense 1 (a militant reformer):

activist

WordNet sense 2 (disposed to warfare or hard-line policies):

hawkish, warlike

WordNet sense 3 (engaged in war):

belligerent, fighting, warring, war-ridden

WordNet sense 4 (not peaceful):

unpeaceful

WordNet sense 5 (showing a fighting disposition):

competitive

WordNet sense 6 (having or showing determination and energetic pursuit of your ends):

aggressive