casus belli

[key-suhs bel-ahy, bel-ee, kah-soos bel-lee]

noun

plural

casus belli 

1. an event or political occurrence that brings about a declaration of war.

casus belli

/ ˈkɑːsʊs ˈbɛliː /

noun

1. an event or act used to justify a war

2. the immediate cause of a quarrel

Word History and Origins

Origin of casus belli¹

1840–50; < New Latin: literally, occurrence of war

Word History and Origins

Origin of casus belli¹

literally: occasion of war

Example Sentences

Polk’s maneuvering into war with Mexico in 1848, complete with a phony border incident as a casus belli, bears comparison with Hitler’s attack on Poland for its purposeful aggression.

Read more on Salon

The reaction was insanely excessive and motivated by some longstanding policy goals that had little to do with the attack but the casus belli wasn't conjured up out of thin air.

Read more on Salon

Only in the past several months has “religious freedom” gained momentum as a casus belli, appearing in Ukrainian and U.S. religious media and now embraced by evangelical Republicans.

Read more on Salon

"We will not respond by talking about 'casus belli' or not, we will respond with concrete actions," he said.

Read more on Reuters

Having lied to her own constituents, fanning their fears of a rigged election, she then claimed their suspicions as a casus belli.

Read more on New York Times

Related Words

• affront 
• harassment 
• indignity 
• insult