Released from detention in July 1939, Saefkow went back to the illegal political work. In Berlin, after the attack on the Soviet Union in 1941, he built up the biggest KPD resistance group, called the "Operative Leadership of the KPD". In 1944, he, Bernhard Bästlein and Franz Jacob led the Saefkow-Jacob-Bästlein Organization which agitated against the war in Berlin munitions plants, and called on people to commit sabotage.