December 7th

The more I learn about WWII in general and Pearl Harbor in specific, the more surprised I am that the Japanese ever attacked us. Yamamoto came up with the idea of a sneak attack, but he had no faith that Japan could win a long, protracted war. Many people believe he said "I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve." Historians doubt that he ever actually said this, but it probably does reflect his thoughts about the war. He did actually say on a number of verifiable occasions "I can run wild for six months...after that, I have no expectation of success."

The Reluctant Admiral relates that "Yamamoto alone" (while all his staff members were celebrating) spent the day after Pearl Harbor "sunk in apparent depression." He is also known to have been upset by the bungling of the Foreign Ministry which led to the attack happening while the countries were technically at peace, thus making the incident an unprovoked sneak attack that would certainly enrage the enemy.

In the end he was right. Midway, the critical naval battle considered to be the turning point of the war, did indeed occur six months after Pearl Harbor, ending June 7th, exactly 6 months later.

Military.com has an interesting story on Pearl Harbor - 9/11 parallels.