Based on archival documents, the book compares the national policy of the USSR and the policy of Nazi Germany towards the Soviet peoples in the pre-war period, including the realization of the political aspirations of the Soviet Union in Western Ukraine, Western Belarus and the Baltic States, the deployment of Nazi policy in the occupied territory of the USSR and countermeasures of the national policy of the Soviet Union, as well as the collaboration of citizens of the USSR, the religious issue in the occupied territory, the ethno-political consequences of Hitler's occupation and the struggle of the Soviet authorities with the nationalist movement in the liberated territory of the country.