casus belli

in a sentence

Perhaps we can prevent the establishment of a German naval base to the south not by declaring war on Turkey, which seems rather a roundabout way of doing it, but by informing the Germans that it would be casus belli.†  (source) Mark Helprin, A Soldier of the Great War, 1991

a pretty woman is a casus belli; a pretty woman is flagrant misdemeanor.†  (source) Victor Hugo, Les Miserables, 1862