The antonyms for "de-militarize" are "militarize," "fortify," "strengthen," "arm," "equip," and "prepare for war." All of these terms hint at the act of increasing and strengthening a military presence, whether it be the arming and training of troops or the building and fortifying of military bases. Unlike "de-militarize," these words suggest an increase in military power and force, rather than a decrease. They also imply a more aggressive and confrontational stance, where the emphasis is on defense and readiness for potential conflict, rather than on peace, compromise, and disarmament.