Casus belli

A casus belli ('occasion for war') is an act or event that provokes or is used to justify war. A casus belli involves direct offenses or threats against the nation declaring the war, whereas a casus foederis involves offenses or threats against its ally—usually one bound by a mutual defense pact. Either may be considered an act of war.

Casus belli

A casus belli ('occasion for war') is an act or event that provokes or is used to justify war. A casus belli involves direct offenses or threats against the nation declaring the war, whereas a casus foederis involves offenses or threats against its ally—usually one bound by a mutual defense pact. Either may be considered an act of war.