Etymology
From Latin cāsus (“occasion”) + bellī (“for war”, literally “of war”).
Pronunciation
- IPA(key): /ˈkeɪ.səs ˈbɛl.aɪ/, /ˌkɑː-/, /-ˈbɛl.i/
Noun
casus belli (plural casus belli or casus bellis)
- An act seen as justifying or causing a war; an act of war.
In ancient times, repeatedly failing to pay tribute by a vassal state was often used as a casus belli by the patron.
1897, Congressional Record, U.S. Government Printing Office, page 664:The Executive, however, can do many acts which would constitute a casus belli, and thus indirectly result in war; but this does not imply in the Executive a concurrent power to declare war, and the war which would result would be one declared by a foreign power.
1977, Alistair Horne, A Savage War of Peace, New York: Review Books, published 2006, page 309:Algiers seethed, and this was the casus belli for the ‘ultras’ to attempt a general strike.
2002, Colin Jones, The Great Nation, Penguin, published 2003, page 138:Furthermore, if the French had airily waved away one potential casus belli, more than enough causes of potential conflict remained embedded in the Aix-la-Chapelle Treaty.
2010, Christopher Hitchens, Hitch-22, Atlantic, published 2011, page 290:Had Saddam taken only the Rumaila oil field and the Bubiyan and Warba islands, there would have been no casus belli.
2022 March 1, Mary Elise Sarotte, “I’m a Cold War Historian. We’re in a Frightening New Era.”, in The New York Times, →ISSN:And Washington needs to communicate clearly with not only its allies but also the American public on the risks involved if spillover from Ukraine into Article 5 territory verges on a casus belli — an event that provokes a war.