Asked in September 1940 by Prime Minister Fumimaro Konoe about projections for a Japan-U.S. war, Admiral Yamamoto replied as follows: “If I am ordered to do it with full effort, I am sure I will be able to run wild for the initial six months or one year. But I am not confident at all if I can do that for two or three years.” By saying so, Yamamoto urged Konoe to avert a war with the United States.
Furthermore, Yamamoto wrote a letter to Navy Minister Shigetaro Shimada after the Hawaii operation was approved. The letter, dated October 24, 1941, stated: “I don’t have any clues as to how the operation will turn out if we employ only an ordinary strategy. In short, we will be forced to simultaneously fight the Battle of Okehazama, the Hiyodorigoe attack and the Battles of Kawanakajima.”
In April 1942, after the successful Pearl Harbor attack, the Naval General Staff vehemently opposed the Midway operation planned by the Combined Fleet. But after heated debates, Yasuji Watanabe, a Combined Fleet staff officer said, “Yamamoto intends to quit his post if this plan is not accepted.”
It was Watanabe’s words, not strategic debates, that prodded the Navy to go ahead with the Midway operation. Chief of the Operations Bureau of the Naval General Staff Shigeru Fukutome said, “If the Commander-in-Chief went as far as saying so, we will leave the matter to him.” His subordinate Seiichi Ito also agreed.
Yamamoto, who knew the national strength of the United States, had only supported the idea of a short, decisive war. He worked out plans for the Pearl Harbor attack and the Midway operation so that Japan could inflict tremendous damage on the enemy fleet, thereby lowering the fighting morale of Americans and bringing them to the negotiation table for peace. But Yamamoto did not make sufficient efforts to ensure that the leaders of the Naval General Staff and the Combined Fleet understood his intentions. According to Toshio Yoshida, a former staff officer of the Imperial Headquarters, Yamamoto “did not think they would understand his true intentions and wanted to avoid trouble caused by misunderstandings.”
Assaults on Midway Island by the Japanese Navy were meant to lure the enemy’s strike forces. But in the actual execution of the operation, the seizure of the island became the foremost goal. The over-confidence and over-optimism of Yamamoto and his staff exacerbated the inconsistencies in the goals of the operation, which resulted in a devastating defeat.