Isoroku Yamamoto

Isoroku Yamamoto (1884-1943) was an admiral of the Imperial Japanese Navy, whose final assignment was Commander-in-Chief, Combined Fleet

Early career

Graduating from the Naval Academy in 1904, he was an ensign during the Russo-Japanese War. During the Battle of Tsushima Strait, he lost two fingers to an explosion. In 1913, he was assigned to the Staff College, indicating he was slated for high rank.

Contact with the West

He was a student at Harvard University betwee 1919 and 1921. He then taught at the Staff College, and then to the air training center.

In 1926, he went to Washington, DC as the Naval Attache. Returning to Japan in 1928, he was promoted to Rear Admiral, in the Naval Affairs Bureau, and was a delegate to the London Naval Conference in 1930.

Navy Ministry

From 1933 to 1936, he headed Japanese naval aviation. In 1936, he was named Vice Minister of the Navy Ministry.

As Vice-Minister, he supported the development of airpower and a halt to building new battleships. At the policy level, he was against the invasion of Manchuria and an alliance with Germany. He apologized personally to the U.S. Ambassador to Japan, in 1937, when the USS Panay was bombed.

Death

On April 13, 1943, American communications intelligence intercepted messages, in a relatively low-level cryptosystem, giving the inspection itinerary of Admiral Isoroku Yamamoto, commanding the Japanese Combined Fleet. There were points along his inspection tour where long-range fighters could intercept and shoot down his aircraft.

The concern was not especially with the idea that this would be an inappropriate assassination. If the interception was successful, it would be a meeting of military warplanes from both sides, and shooting down a senior commander, in uniform, while in a combat theater. One concern was that the Japanese might realize that the U.S. had broken their secure communications, which would cause them to change systems and risk a major source of intelligence. Another would be Yamamoto's successor -- might a more able admiral replace him? Edwin Layton, the Pacific Command intelligence officer, presented the risks and benefits to Nimitz. Layton, who personally knew Yamamoto, wrote that he said there was "only one Yamamoto." Layton also wrote "it was impossible for me not to feel for Admiral Yamamoto with a certain sense of fondness." Nevertheless, Layton considered that, if Japan lost an immensely admired commander as well as their best strategist, the effect would be equivalent to a major fleet victory. Layton believed that the U.S. could leak a report that Yamamoto's tour had been reported by Australian coastwatchers, and probably make the Japanese, who were generally overconfident about their communications security, believe their cryptosystem was secure. No operations were planned in the short term, so U.S. forces would have time to attack a new cryptosystem if the Japanese did change. Nimitz, after clearing the decision with the Secretary of the Navy and the President, authorized the mission.

On April 18, Yamamoto died when a force of 18 U.S. Army Air Force P-38 Lightning fighters intercepted and shot down the two bombers carrying staff officers, which were escorted by six Japanese fighters.

There was only one Yamamoto, and no one is able to replace him His loss is an unsupportable blow to us — Adm. Mineichi Koga, Yamamoto's successor

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