War

War is a conflict involving the organized use of weapons and physical force by states or other large-scale groups. Warring parties usually hold territory, which they can win or lose; and each has a leading person or organization which can surrender, or collapse, thus ending the war. Until the end of World War II, participants usually issued formal declarations of war.

The term is also used in constructs naming other forms of conflict, where the goal is the submission of one part by the other: trade war, psychological war, cold war.The word war is sometimes used rhetorically to refer to a campaign against something, without territory to capture or an authority to defeat; e.g. the war on drugs, the war on terror.
Other terms for war, often used euphemistically, include armed conflict, hostilities, and police action (note). A time when no formal war is taking place, although there may be international and internal tensions, is called peacetime or peace.

Wars usually take the form of a series of military campaigns between two opposing sides involving a dispute over, amongst others issues, sovereignty, territory, resources, religion, or ideology. A war to liberate an occupied country is called a "war of liberation"; a war between internal factions within a state is a civil war.