warfare, violent conflict between armed enemies. In modern times warfare has usually been conducted by the armed forces (e.g., army, navy, and air force) of a nation or other politically organized group. The way in which war is carried out is governed by the principles of strategy and tactics, by the type of weapons employed (see articles on individual weapons), and by the type of communication and transportation facilities available. Thus, throughout history the methods of warfare have changed. See air forces; amphibious warfare; chemical warfare; biological warfare; fortification; mechanized warfare; trench warfare; guerrilla warfare; siege.