Prior to the Attacks
The relationship between the U.S. and Japan wasn't always bad, they were actually allies in World War I. The U.S were an ally to China too, and watched the war unfold between China and Japan. Then in 1937, the Japanese invaded Nanjing, China and attacked a U.S. battleship, which killed three and wounded dozens. This event produced many disturbing videos, ruining America's vision of Japan. In hopes of stopping further attacks on China, the U.S. invaded Japan and took their military necessities. To their dismay, Japan raided French Indochina in 1940.
Pearl Harbor five weeks before attacks, United States Navy
In July of 1941, then U.S. President, Franklin D. Roosevelt announced a trade embargo on oil. At the time, Japan relied on imported oil for 90% of their supply. When this was no longer available, their military was unable to run. The Japanese were furious with America for interfering with their plan to dominate Asia and felt the only option was to attack the U.S., claim Asia's resources, and take over.
Japanese Military, Keystone-France/Gamma-Keystone/Getty Images
Japanese Leader Isoroku Yamamoto
The Japanese military trained and prepared for a year before the attack. Their military attack forces included 420 planes and six aircraft carriers. Imperial Navy Officer, Admiral Isoroku Yamamoto, was one of the few people who thought that attacking America would be a success. He lived in the U.S. for several years and came to understand the military and economic power there. He came up with a grand plan that called for hundreds of planes to be brought with carriers all around Pearl Harbor. His plan also involved bombers, fighter planes, and a big torpedo.