What is a Casus Belli?
Casus belli is a Latin phrase which literally means “occasion for war.” It is often translated as a “cause for war” or a “case for war,” and it is used to describe an incident which becomes a catalyst for a military conflict. As a general rule, a nation must provide the international community with a casus belli before making war on another nation, and if a nation expects to invoke the assistance of allies, a casus belli is critical. The term “casus bellum” is also used in the same way. In some cases, a casus belli may be an incident which directly provokes a war, such as a preemptive strike or invasion. In this case, the international community often supports the conflict, under the argument that a nation must defend itself when it is threatened. In other cases, a casus belli may be a pretext or justification for war, in which case the grounds for war may be a bit more murky, and a nation may have trouble convincing the international community that its actions are appropriate.
