At first Paulus refused to collaborate with the Soviets. However, after the attempted assassination of Hitler on 20 July 1944, he became a vocal critic of the Nazi regime while in Soviet captivity, joining the Soviet-sponsored National Committee for a Free Germany appealing to Germans to surrender. He later acted as a witness for the prosecution at the Nuremberg Trials. He was allowed to move to the German Democratic Republic in 1953, two years before the repatriation of the remaining German POWs.