What is "co-belligerence"

Co-belligerence is the waging of a war in cooperation against a common enemy without a formal treaty of military alliance.

Co-belligerence is a broader and less precise status of wartime partnership than a formal military alliance. Co-belligerents may support each other materially, exchange intelligence and have limited operational coordination. The aims of war in which co-belligerents participate may differ considerably.

The term co-belligerence indicates remoteness between the co-belligerent parties, cultural, religious, ideological or otherwise, whereas alliance indicates a corresponding closeness.