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 Korea,^[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]