Various writers have speculated that the information allowed the release of Siberian divisions for the Battle of Moscow, where the German Army suffered its first strategic defeat in the war. To that end, Sorge's information might have been the most important military intelligence work in World War II. However, Sorge was not the only source of Soviet intelligence about Japan, as Soviet codebreakers had broken the Japanese diplomatic codes and so Moscow knew from signals intelligence that there would be no Japanese attack on the Soviet Union in 1941.