ca·sus bel·li
noun/ˌkeɪsəs ˈbelaɪ/, /ˌkɑːsʊs ˈbeliː/
/ˌkeɪsəs ˈbelaɪ/, /ˌkɑːsʊs ˈbeliː/
(plural casus belli)
(formal)- an act or situation that is used to justify a war
交战理由;开战借口 Word OriginLatin, from casus ‘fall’ and belli, genitive of bellum ‘war’.