The United States had recently embargoed the Japanese because of their war in China and a number of other actions that had antagonized the United States (the Panay incident , seizing French Indochina). The Japanese needed American oil to continue their war effort (Japan was not rich in resources). So the Japanese decided to attack Pearl Harbor in order to force the Americans into war, and hopefully win, which would give Japan dominance in the pacific and allow them to get oil both from trade with America but mostly from the Dutch East Indies.

Pearl Harbor was chosen because it was the base for the United States pacific fleet, and it held the oil reserves for the pacific fleet. Taking out these would cripple America's war effort for a significant amount of time. Unfortunately for Japan, when they attack Pearl Harbor the Carriers were out doing experiences and the Japanese did not attack the Oil reserves, meaning Pearl Harbor in the grand scheme of things accomplished very little.

Sources: John Keegan-The Second World War

John Costello- The Pacific War

Edward Drea- Japan's Imperial Army

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