What were Japan's motivations for attacking Pearl Harbor on December 7 1941?

Answer 1

Japan was engaged in a war with China. Early in 1941 the United States had stopped exporting oil to Japan. Oil is a strategic material for any mechanized military force, and Japan had no domestic sources of oil. To obtain petroleum to supply their army in China, the Japanese decided to occupy the Dutch East Indies (now indonesia), where oil fields were in operation. As the Netherlands was then occupied by Germany, this could also be seen as an action in support of an ally. Japanese planners believed that they would have to neutralize British forces in the region if they were to keep control of the Indonesian oil fields, and would thus have to control Hong Kong, Singapore and other British outposts, as well as the Philippines(then under US control). It had been a point of Japanese Naval doctrine for many years that Japan would eventually fight the United States. As an attack on British and Dutch possessions in east and southeast Asia, not to mention the Philippines, would surely bring the US into the war, the attack on Pearl Harbor was intended to destroy the US Pacific Fleet and thus prevent US interference in Japanese naval operations during the first half of 1942. Some planners hoped that a decisive destruction of the fleet would lead the US to seek peace in short order. As it happened, the battleship formation of the Pacific Fleet was severly damaged, but the aircraft carriers were at sea and not damaged at all. This left the US with a significant, though much reduced, naval presence in the Pacific. It also forced the US navy to use, and eventually accept, carrier tactics more quickly than would have been done had the battle ships not been so heavily damaged.