Why didnt the US think that Japan would attack Pearl Harbor?

Answer 1

In 1940, the US Navy's Battleship Fleet transferred to Pearl Harbor, from it's old base in Los Angeles (Long Beach), California. Obtain the book: "Day of Deceit: The Truth About FDR and Pearl Harbor." (2000); By Robert B. Stinnett.

Answer 2

Japanese naval strategy before the war was to wait for the US to attack with their battle fleet, the Japanese navy would attack the US Navy as they sailed across the Pacific, gradually whittling them down before they came within striking distance of Japan.

The US knew this, so an attack at Pearl was not contemplated until it was too late.

Answer 3

The Japanese knew that the US was already aiding Britain against Germany, Japan's ally, and might enter the war at any time. But before the US was prepared for open conflict, the base at Pearl Harbor presented an opportunity to delay any intervention by the powerful US Navy. This would allow Japan to complete their conquests and establish strong bases in the occupied territories, from which the US would find it impossible to remove them.

If the attack had fully succeeded, the mainly isolationist US might have been deterred from an unpopular war, or been more concerned with defending its own coasts and territories. But, as the Japanese Admiral Yamamoto had feared, the attack backfired, and the US, its public outraged, geared up its armed forces to strike back at the Japanese Empire.