Ultra in the Pacific : How Breaking Japanese Codes and Cyphers Affected Naval Operations Against Japan 1941-45

Ultra, the name given to information gained from the deciphering of messages passed by the enemy in code during World War II, was an invaluable asset to the Allies. But its application gave rise to other problems. If the information gained was used too freely, the enemy would soon suspect that their radio traffic was being intercepted and read, and would take the necessary counter-measures. Fortunately for the Americans in the Pacific, the Japanese believed that it was not possible for Westerners to learn their language. Lulled by this misapprehension into a false sense of security, they could only ascribe to luck or coincidence the remarkable frequency with which the Americans intercepted their plans. The war in the Pacific has had many chroniclers, but the secret of Ultra remained guarded for many years and only recently has it become possible to assess its effect in detail. John Winton's analyses of the records now available are here combined with his knowledge of the naval history of World War II to tell what exactly the Allies did learn from Ultra in the Pacific War, and to what use that knowledge was put. Winton is a novelist and historian who specializes in stories of the sea. His books include "Ultra at Sea" (to which this is a companion volume), "The Forgotten Fleet" (a history of the British Pacific Fleet in 1944-45) and "Air Power at Sea 1939-45".