Dec 7th 1947

In the summer of 1941, after Japanese expansion into French Indochina, the U.S. ceased oil exports to Japan, in part because of new American restrictions on domestic oil consumption. President Franklin D. Roosevelt had earlier moved the Pacific Fleet to Hawaii and ordered a buildup in the Philippines, hoping to deter Japanese aggression in the Far East. The Japanese high command was certain, though mistakenly so, an attack on the United Kingdom's colonies would bring the U.S. into the war, so a preventive strike appeared to be the only way Japan could avoid U.S. interference in the Pacific. While the attack accomplished its intended objective, it was completely unnecessary--unbeknownst to Isoroku Yamamoto, who conceived the original plan, the U.S. Navy had decided to abandon any intention of 'charging' across the Pacific towards the Philippines at the outset of war back in 1935 (in keeping with the evolution of War Plan Orange). They instead adopted "Plan Dog" in 1940, which emphasized keeping the Imperial Japanese Navy (IJN) out of the eastern Pacific and the shipping lanes to Australia, while the U.S. concentrated on defeating Nazi Germany.

The attack was one of the most important engagements of World War II. Occurring as it did before a formal declaration of war, it pushed U.S. public opinion from isolationism to an acceptance war was unavoidable, as Roosevelt called December 7, 1941 "... a date which will live in infamy."