Molotov-Ribbentrop pact
About 250,000 to 454,700 Polish soldiers and policemen were captured and interned by the Soviet authorities. About 125,000 were imprisoned in camps run by the NKVD, and 43,000 soldiers born in western Poland, which was under German control, were transferred to the Germans. In turn, the Soviets received 13,575 Polish prisoners from the Germans, which showed how close the co-operation was between the Germans and the Soviets.