Isokoru Yamamoto, the son of a schoolmaster, was born in Japan on 4th April 1884. He attended the Japanese Naval Academy and graduated as seventh in his class. He joined the Japanese Navy and as an ensign he took part in the Russo-Japanese War. Yamamoto was on board a cruiser during the destruction of the Russian Fleet at Tshushima in 1905.
In 1914 Yamamoto was promoted to lieutenant commander and assigned to the Imperial Navy Headquarters in Tokyo. Two years later he was sent to the United States where he studied economics at Harvard University. While in America he also took a keen interest in military aviation.
In 1930 Yamamoto took command of the 1st Air Fleet and the following year was promoted to rear admiral in charge of the navy's technical service. Yamamoto, who had learnt to fly, became convinced that future wars would be decided by air power and embarked on a massive new building programme.
In 1934 the Japanese built around 445 aircraft. This increased to 952 (1935), 1,181 (1936), 1,511 (1937), 3,201 (1938), 4,467 (1939) and 4,768 (1940). This included fighters, torpedo-bombers and dive-bombers. The most important of these were the fighters Mitsubishi A5M, Nakajima Ki-27, and the Mitsubishi A6M and the bombers Mitsubishi ki-21 and Mitsubishi G3M.
As vice minister of the Japanese Navy Yamamoto arranged for the building of two modern aircraft carriers, Shokaku and the Zuikaku.
In 1938 Yamamoto was appointed a Minister of the Navy and the following year Yamamoto was promoted to admiral and became commander in chief of the Combined Fleet. In this position he attempted to improve the training of men in the Japanese Navy. However, he made a crucial mistake of not fitting Japanese ships with radar.
Yamamoto was opposed the signing of the Tripartite Pact with Nazi Germany as he feared it would lead to war with the United States. He told the Japanese prime minister, Fumimaro Kondoye, that the navy would do well during the first six months but did not believe the country could win a long-term war.
In the early months of 1941, Yamamoto, under instructions from his government, began planning the war with the United States. Yamamoto feared that he did not have the resources to win a long war and therefore advocated a surprise attack on the US Pacific Fleet at Pearl Harbor. Yamamoto's plan was eventually agreed by the Japanese Imperial Staff and the strike force under the command of Vice Admiral Chuichi Nagumo sailed from the Kurile Islands on 26th November, 1941.
Nagumo's fleet was positioned 275 miles north of Oahu. On Sunday, 7th December, 1941, 105 high-level bombers, 135 dive-bombers and 81 fighter aircraft attacked the the US Fleet at Pearl Harbor. In their first attack the Japanese sunk the Arizona, Oklahoma, West Virginia and California. The second attack, launched 45 minutes later, hampered by smoke, created less damage.
In two hours 18 warships, 188 aircraft and 2,403 servicemen were lost in the attack. Luckily, the navy's three aircraft carriers, Enterprise, Lexington and Saratoga, were all at sea at the time. The following day, President Franklin D. Roosevelt and a united US Congress declared war on Japan.
In the summer of 1942 Yamamoto decided to try and capture the US base on Midway Island. He believed that the Japanese Air Force would be able to launch air attacks on the US Fleet at Pearl Harbor. Yamamoto devised a complex plan where the Combined Fleet was split into eight task groups. Two of these groups made a diversionary attack on the Aleutian Islands. The rest of the fleet led by Yamamoto, Vice Admiral Chuichi Nagumo and Vice Admiral Nobutake Kondo, would head for Midway.
Unknown to Yamamoto the US intelligence service and broken the Japanese communication code and informed Admiral Chester Nimitz of the Japanese plans. Nimitz was able to assemble two task forces under Admiral Frank Fletcher and Rear Admiral Raymond Spruance. With the carriers Yorktown, Enterprise and Hornet, eight cruisers, and fifteen destroyers, they also headed for Midway.
On 3rd June, 1942, 100 aircraft from Nagumo's carrier force bombed Midway. The US Marine fighters were outnumbered and were unable to stop extensive damage being caused. While the Japanese aircraft were being rearmed they were attacked by carrier planes from Spruance's Task Force.
While this was taking place Yorktown and Enterprise arrived and scored hits on the Japanese ships, Akagi, Soryu and Kaga. The Hirpu managed to sink the Yorktown before it was set afire by the Enterprise. The Japanese Navy had now lost all four of her aircraft carriers and Yamamoto was forced to order a withdrawal.
Yamamoto now had to organize what was left of his forces to support the 15,000 Japanese troops blockaded on Guadalcanal. Attempts to land large numbers of Japanese troops ended in failure in October 1942. The naval battle at Guadalcanal (12-14 November) ended Japanese efforts to recapture the island.
Yamamoto made plans to visit the Japanese controlled Bougainville on 18th April. He sent out details of his itinerary and this information was intercepted by US intelligence. When Admiral Chester Nimitz heard the news he consulted with William Knox, the Navy Secretary, and Admiral William Halsey, and it was decided to try an assassinate the man responsible for Pearl Harbor.
Operation Vengeance began on 18th April 1943, when 18 aircraft led by Major John W. Mitchell, went out to find the plane carrying Yamamoto. At 9.30 am the US pilot, Thomas G. Lamphier, identified Yamamoto's aircraft approaching Kahili Field on Bougainville. Two bursts from his guns hit the target and the aircraft crashed into the jungle.
The Japanese government did not announce the death of Isokoru Yamamoto until 21st May 1943. He was replaced as commander in chief of the Combined Fleet by Mineichi Koga.