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Synonyms

casus belli

American  
[key-suhs bel-ahy, bel-ee, kah-soos bel-lee] / ˈkeɪ səs ˈbɛl aɪ, ˈbɛl i, ˈkɑ sʊs ˈbɛl li /

noun

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


casus belli British  
/ ˈkɑːsʊs ˈbɛliː /

noun

  1. an event or act used to justify a war

  2. the immediate cause of a quarrel

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

Noun Inflected Forms

Etymology

Origin of casus belli

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

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

In his speech announcing the war, Mr. Trump explained the extensive casus belli to the American people.

From The Wall Street Journal Mar. 2, 2026

Rather, this narrow goal may be intended to serve as an official casus belli, giving Russian diplomats something to cite, however implausible, particularly at the United Nations.

From New York Times Feb. 24, 2022

In such a febrile atmosphere, the risk of a misunderstanding or unplanned escalation is greater, and Russia could use such an incident as a casus belli.

From Reuters Jan. 14, 2022

He could well seize on some alleged affront in the negotiations themselves as a casus belli.

From Washington Post Dec. 14, 2021

Others attacked this conclusion, and the skeletons became one of the casus belli of the evolution wars.

From "1491" by Charles C. Mann

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