Isoroku Yamamoto, Commander in Chief of the Japanese Combined Fleet, had few illusions about the ultimate success of a war against the United States. He had studied at Harvard and served as a naval attaché in Washington and knew America’s strength. But if war had to come he meant “to give a fatal blow to the enemy fleet” when it was least expected, at the outset. By that act he hoped he could win his country six months to a year during which it might establish its Greater East Asia Co-Prosperity Sphere and dig in.