bel·lig·er·en·cy /bə-'li-jə-rən-sē/ n: the state of being at war or in conflict; specif: the status whereby a recognized military force is granted the protection of the international laws of war
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.
affray, aggression, aggressiveness, altercation, animosity, antagonism, assault, attack, battling, bellicosity, belligerance, clashing, combat, combativeness, conflict, contentiousness, contestation, controversy, disagreement, discord, disputation, dissension, disturbance, embroilment, encounter, enmity, feud, fighting, fracas, hostility, impugnation, impugnment, inimicality, malevolence, martiality, melee, militancy, opposition, oppugnancy, oppugnation, pugnaciousness, pugnacity, resort to arms, revengefulness, riot, rivalry, scuffle, siege, sparring, state of siege, state of war, strife, time of war, tumult, tussle, unpeacefulness, violence, warfare, warlikeness, wartime, wrangle
associated concepts: adverse possession, belligerency de facto, international law, national defense
argument (contention), conflict, ill will, strife
Burton's Legal Thesaurus. William C. Burton. 2006
the state of carrying on war.
Collins dictionary of law. W. J. Stewart. 2001.