casus belli


plural casus belli
: an event or action that justifies or allegedly justifies a war or conflict

Examples of casus belli in a Sentence

Recent Examples on the Web In the run-up to the Iraq War, diplomacy and weapons inspections became a means to an end: building a casus belli. Foreign Affairs, 18 Oct. 2012 State media claimed without providing any evidence that the hospital was being used as a base for the Azov Battalion, a small far-right nationalist group often used as casus belli by Putin for false claims that the Ukrainian government is rife with Nazis. Michael Biesecker, Erika Kinetz, Beatrice Dupuy, Anchorage Daily News, 26 Mar. 2022 In each instance, the casus belli is complicated stuff. Anthony Lane, The New Yorker, 14 Oct. 2022 Critical voices challenging Putin’s casus belli and highlighting Russia’s isolation, the atrocities committed daily by Russian troops and the disastrous costs of the conflict for Russia have been all but silenced. Daniel Beer, Washington Post, 29 Sep. 2022 Less can be said of the muddled casus belli, as Dahomey’s struggle for independence unpersuasively evolves into a proto-pan-African struggle for abolition. Julian Lucas, The New Yorker, 16 Sep. 2022 By exposing this plan, the Biden administration sought to undermine its emotional power and stop the Kremlin from manufacturing a casus belli, or justification for war. Scott Radnitz, The Conversation, 17 Feb. 2022 India was itching to intervene militarily but lacked a cast-iron casus belli. Tunku Varadarajan, WSJ, 18 Mar. 2022 The Tonkin Gulf incident, which provided a casus belli for the Vietnam War, gets a single sentence. Fred O’Brien, National Review, 3 Mar. 2022 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'casus belli.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


New Latin, occasion of war

First Known Use

circa 1841, in the meaning defined above

Time Traveler
The first known use of casus belli was circa 1841

Dictionary Entries Near casus belli

Cite this Entry

“Casus belli.” Dictionary, Merriam-Webster, Accessed 2 Dec. 2023.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!