Les Misérables vocabulary

"When your American friends come to Rome," she said coldly—as though I were in the habit of importing Yankee girls wholesale—"they must do as Rome does." But when I at last pointed out that Ida, as an American citizen, could appeal to her minister if I attempted to turn her out, and that we might find ourselves the centre of an international quarrel—possibly even a casus belli—she finally yielded with a struggle.

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No quarter, war to the death! a pretty woman is a casus belli; a pretty woman is flagrant misdemeanor.

Victor Hugo. Les Misérables