WordNet sense 1 (an aggressive willingness to compete):

competitiveness

WordNet sense 2 (exert oneself continuously, vigorously, or obtrusively to gain an end or engage in a crusade for a certain cause or person; be an advocate for):

agitate, campaign, crusade, press, push

WordNet sense 3 (make a strenuous or labored effort):

struggle

WordNet sense 4 (the act of fighting; any contest or struggle):

combat, fighting, scrap, combat

WordNet sense 5 (fight against or resist strongly):

defend, oppose, fight back, fight down

WordNet sense 6 (be engaged in a fight; carry on a fight):

contend

WordNet sense 7 (a hostile meeting of opposing military forces in the course of a war):

battle, conflict, engagement, conflict