Casus Belli

Casus Belli may be described as the last political straw that breaks the camel's back, and may consist of any act on the part of one nation towards another which forms the pretext for a war. Sometimes it is a well-understood step, at others the veriest trifle may determine a war. In the war between England and America in 1812 a claimed right of search, in the Crimean question the crossing of a river, in the Franco-German war a slight to an ambassador, formed the pretext.