casus belli
/ˌkeɪsəs ˈbɛlʌɪ
/ /ˌkɑːsʊs ˈbɛli /noun (plural same)
An act or situation that provokes or justifies a war.As the Romans liked a casus belli to justify their aggressive activities, it is not always possible to be certain about the real circumstances behind their intervention....
- France countered by getting Russia to propose a general congress, intended to isolate Austria and provoke a casus belli.
- The failure to disarm is probably a casus belli.
Origin
Latin, from casus (see case1) and belli, genitive of bellum 'war'.