Casus Belli
/ˈkɑː.sus ˈbɛl.i/noun
An event or act that provides a justification for war.
Did you know?Casus belli is a classical Latin legal phrase, and its power comes from the Roman habit of framing war as a response to an “incident” rather than naked aggression.
Etymological Timeline
Proto-Indo-European
PIE
*gʷelH-
“to strike, wound; the root behind violence and war-related Latin words”
Proto-Indo-European
PIE
*deuk-
“to lead; source of Latin ducere, which appears in related war-and-legal vocabulary like inducement and deduction”
Latin
LA
casus
“a fall, chance, occurrence, event”
Latin
LA
bellum
“war”
Classical Latin
LA
casus belli
“an occasion or event for war; a legal pretext for conflict”
Modern English
EN
casus belli
“a justification or pretext for war”
Explore more surprising origins