War II. In 1941, two years after the border war, Japan and the Soviet Union signed a neutrality pact. Later in 1941, Japan would consider breaking the pact when Nazi Germany invaded the Soviet Union (Operation Barbarossa), but they did not, largely due to the defeat at Battle of Khalkhin Gol, even though Japan and Nazi Germany were part of the Tripartite Pact. At Yalta in February 1945, Stalin promised Roosevelt that the USSR would enter the war against Japan 90 days after the defeat of Germany, which took place in May. It met that timetable by shifting large forces across Siberia. In April 1945, Moscow annulled the neutrality pact. The Soviet invasion of Manchuria began on August 8, 1945, after the atomic bombing of Hiroshima (August 6). The Soviet Union planned an invasion of Hokkaido, but it was never carried out because of opposition from the United States. Richard Sorge: Invaluable spy Richard Sorge (1895 – 7 November 1944) was a German journalist and Soviet military intelligence officer who was active before and during World War II and worked undercover as a German journalist in both Nazi Germany and the Empire of Japan. His codename was "Ramsay" (). A number of famous personalities considered him one of the most accomplished spies. Sorge is most famous for his service in Japan in 1940 and 1941, when he provided information about Hitler's plan to attack the Soviet Union in 1941. Then, in mid-September 1941, he informed the Soviets that Japan would not attack the Soviet Union in the near future. A month later, Sorge was arrested in Japan for espionage. He was tortured, forced to confess, tried and hanged in November 1944. Stalin declined to intervene on his behalf with the Japanese. He was posthumously awarded the title of Hero of the Soviet Union in 1964. 1946–1960s: Restoration of relations Due to the invasion, 56 islands of the Kuril chain, as well as the southern half of Sakhalin (i.e. the Northern Territories), were in 1946 incorporated into the Soviet Union. The USSR created a South-Sakhalin Province in the Khabarovsk Region of the Soviet Union. This annexation was never recognized by Japan and prevented the conclusion of a Soviet-Japanese World War II peace treaty and the establishment of closer relations between the two states. The Soviet Union refused to return these territories claiming that it feared that such a return would encourage