Within nations occupied by the Axis powers in World War II, some citizens and organizations, prompted by nationalism, ethnic hatred, anti-communism, antisemitism, opportunism, self-defense, or often a combination, knowingly collaborated with the Axis Powers.Some of these collaborators committed war crimes, crimes against humanity, or atrocities in the Holocaust.

The Ukrainian collaborationist forces were composed of an estimated number of 180,000 volunteers serving with units scattered all over Europe. Russian émigrés and defectors from the Soviet Union formed the Russian Liberation Army or fought as Hilfswillige within German units of the Wehrmacht primarily on the Eastern Front . [7]