Undeclared war

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An undeclared war is a military conflict between two or more nations without either side issuing a formal declaration of war. The term is sometimes used to include any disagreement or conflict fought about without an official declaration. Since the United Nations' police action in the Korean War,^[1] some governments have pursued disciplinary actions and limited warfare by characterizing them as something else such as a military action or armed response.

Under customary international law, it is not necessary to declare war—simply beginning hostilities is sufficient to make belligerent intentions clear.^[2]