War game a military exercise carried out to test or improve tactical expertise; a simulated military conflict carried out as a game, leisure activity, or exercise in personal development. The term is recorded from the early 19th century, and is the equivalent of the German kriegspiel.
war to end wars a war which is intended to make subsequent wars impossible; in particular, applied to the First World War. The War That Will End War (1920) was the title of a book by H. G. Wells.
See also the dogs of war, all's fair in love and war, honours of war, just war, laws of war, truth is the first casualty of war.