User:RealKorgi/Sandbox (Simple Wikipedia)

Planning for an attack on Pearl Harbor had been planned since early 1941. Isoroku Yamamoto came up with the plan in order to protect Japan's attack on Southern Asia. He got permission to plan and train for an attack. To do so, he had to argue with the Imperial Japanese Navy General Staff. He only got permission because he threatened to quit his job. Full-scale planning started in Spring 1941. The planning was under the guidance of Rear Admiral Ryūnosuke Kusaka, with assistance from Captain Minoru Genda. The planners looked to the 1940 British air attack on the Italian fleet at Taranto for help. This was because the British had successfully attacked ships in port there.

Over the next several months, things progressed as planned. However, Emperor Hirohito did not approve the attack plan until November 5. This is because he wanted to discuss the matter over a set of Imperial Conferences. Final approval was not given until December 1st. This was because a majority of Japanese leaders warned the emperor about the "Hull Note. They said it would, "destroy the fruits of the China incident, endanger Manchukuo and undermine Japanese control of Korea".

By late 1941, many people thought war between the U.S. and Japan would come soon. A Gallup poll just before the attack on Pearl Harbor found that 52% of Americans expected war with Japan, 27% did not, and 21% had no opinion. Many U.S. bases in the pacific were put on alert in this period. However, U.S. leaders doubted that Pearl Harbor would be attacked. They expected Japan to attack the Philippines. This was because the Philippines were in a important position in the Pacific. The islands had many air bases and a large naval port. These would threaten Japanese shipping in Southern Asia. They also incorrectly thought Japan wasn't capable of multiple attacks at once.