Richard Sorge was a German enraptured with communism. In 1929, he became a Soviet spy in the Far East. Operating in Japan from 1933 until his arrest in late 1941, Sorge became a close adviser to the German ambassador in Tokyo and built a formidable espionage machine at a time when all foreigners were under close scrutiny from Japanese authorities. Sorge’s main mission was to find out whether Japan was planning to attack the Soviet Union. But his most famous report was one that warned of Germany’s imminent invasion in 1941—a warning that was dismissed by his bosses, who were fearful of contradicting Stalin’s belief that Hitler would not breach the Nazi-Soviet Nonaggression Pact. Matthews’ meticulously researched book draws in particular on materials from Soviet intelligence archives that have never before been accessed by a Western historian. These documents show that, despite the vital intelligence he provided, the Soviets always regarded Sorge as a potential traitor. Matthews’ book is a spy thriller that doubles as an enthralling history of revolutionary Germany in the 1920s, Tokyo during the country’s prewar militarization, and Moscow in the 1930s, where Stalin’s mass terror consumed, among others, seven of Sorge’s military intelligence bosses.