wartime collaboration

Wartime collaboration is the voluntary cooperation of local populations, officials or combatants with the enemy against their own state, often for personal gain, ideology or survival. It is widely considered as a form of betrayal and a crime (treason) as it is viewed as a breach of loyalty that compromises the safety of the citizens and sovereignty of the state. As historian Gerhard Hirschfeld says, it "is as old as war and the occupation of foreign territory".

The term collaborator dates to the 19th century and was used in France during the Napoleonic Wars. The meaning shifted during World War II to designate traitorous collaboration with the enemy. The related term collaborationism is used by historians who restrict the term to a subset of ideological collaborators in Vichy France who actively promoted German victory.