Top Japanese officials felt that war with the United States was inevitable, but with a large American fleet in the Pacific stationed at Pearl Harbor on the island of Oahu, war was going to be difficult if Japan was on the defensive. It would have been to Japan's advantage if they were the ones to pick the time and place of battle, as they went on to do. Admiral Isoroku Yamamoto came up with the idea of annihilating the entire American pacific fleet in one single blow (Essential Pearl Harbor).
Beginning in the early months of 1941, Japanese aircraft carrier pilots began training for a Top Secret mission involving an air raid on a fleet of ships using tactics that met two major criteria. The attack was to use a huge amount of naval aviation forces, and it was to achieve complete surprise on its enemy. Japanese leaders felt that if the attack met that criterion, Japan would dominate the Pacific Ocean and have control over all of the Far East. As the training continued, the plan became more and more detailed. In the latter part of February 1940, Adm. Isoroku Yamamoto gave Comdr. Minoru Genda, the Japanese Prime Minister, a detailed official report on the plan of the attack. It contained ten main proposals: It must be a surprise attack; U.S. carriers are the main objective; U.S. aircraft on the Island of Oahu are an objective; every available Japanese Carrier should take part in the operation; all types of attack aircraft should be used; Japanese fighters should play an active role in the attack; the attack should be early in the morning; refueling vessels at sea is necessary; all planning must be kept secret; and finally, it will be a full scale invasion. Yamamoto, who was one of the main contributors to the plan, wanted only to cripple the American pacific fleet while Genda wanted to obliterate it (Essential Pearl Harbor). .
In October of 1941, Commander Minotu Genda gave the final go ahead to Yamamoto's plan, which was to be commanded by Admiral Chuichi Naguro.