In 1941, Harnack sent the Soviets information about the forthcoming invasion. That same year, he wrote for the resistance magazine, "Die innere Front" ("The Inner Front"), the twice-monthly newspaper written in six languages that was created by John Sieg. In 1942, Harnack produced a study called "Das nationalsoialistische Stadium des Monopolkapitalismus" (The National stage of monopoly capitalism), published in "Die innere Front", which described the Gestapo as a tendentious and antigovernment economic treatise, and was read as far as Munich and Hamburg.