In 1940 the U.S. Army Signal Intelligence Service broke the Japanese diplomatic code. In 1975 Ōshima Hiroshi, Japan's ambassador to Berlin during World War II, died, never knowing that the hundreds of messages he transmitted to Tokyo had been fully decoded by the Americans and whisked off to Washington, providing a major source of information for the Allies on Nazi activities. Resurrecting Ōshima's decoded communications, which had remained classified for several decades, Carl Boyd provides a unique look at the Nazis from the perspective of a close foreign observer and ally. He uses Ōshima's own words to reveal the thought and strategies of Adolf Hitler and other high-ranking Nazis, with whom Ōshima associated. In addition to providing illuminating insight into Nazi activities and attitudes—military buildup in North Africa, the unwillingness to accept a separate peace with the Soviets—Boyd illustrates the functions of MAGIC. He demonstrates how that intelligence, gathered by teams of American cryptographers, influenced Allied strategy and helped bring about the downfall of Hitler and his Japanese confidant.