Why Did Japanese Attack Pearl Harbor

This surprise attack was incredible because U.S. Army rader site at Opana Point, on Oahu, was tracking incoming aircraft, and the Navy discovered a submarine close to Pearl Harbor. Furthermore, US was able to break a Japanese code, which allows them to read messages of Japanese Navy. It was a well-prepared attack by the Pearl Harbor Task Force, the Kido Butai, which allowed them to execute airstrikes before the detection.

In January 1941, Admiral Isoroku Yamamoto proposed a attack on Pearl Harbor using aircraft carriers even though the strategy of Japanese navy was intended to be defensive, not offensive. This meant that they were planing to defeat US ships close to the main land of Japan until US navy weakens its power. This proposal made significant change in the Japanese navy. US naval intelligence was not able to detect this significant shift of the
Their activities helped to hide that the Japanese navy changed its strategy. Furthermore, it hindered the location of Japanese carriers. As a result, the American stations in Hawaii and the Philippines was sending summaries to Admiral Kimmel as "nothing on the carriers" or "no information." US navy was uncertain where the ships were because of almost no transmissions. They concluded that there was no immediate threat to pearl Harbor. Another institution that was critical to the success was Japanese radio intelligence. It keeped the Kido Butai informed of any changes of US forces in Hawaii and warned if its presence was known.

The United States was aware of the Japanese threat to attack in Southeast Asia, but they thought Japan's main target was Malaya or Philippines, not Pearl Harbor. It was not a part of their calculations. In summary, I could say that preparedness of Japanese navy and unpreparedness of US navy led the result of the successful attack. Gathering information was critical to prepare the