From Halopedia, the Halo wiki
War is any protracted, large-scale, violent conflict; containing several battles. By extension, the word can be used for any long-term struggle. A group of combatants and their support is called an army on land, a navy at sea or in space, and air force in the air. Wars may be prosecuted simultaneously in one or more different theaters. Within each theater, there may be one or more consecutive military campaigns. A military campaign includes not only fighting but also intelligence, troop movements, supplies, propaganda, and other components. A smaller continuous conflict is traditionally called a battle, although this terminology is not always applied to conflicts involving aircraft, missiles or bombs alone, in the absence of ground troops or naval forces.
List of wars