Following the annexation of Hawaii in 1898, the United States decided to expand its military presence in the pacific region.  As a result, it established a significant naval force in the area and developed a large naval base that would serve as the home for the US Pacific forces. Over time, the harbor was transformed into a critical military installation, complete with dry docks, ship repair centers, piers, and major battleship docking stations. By 1940, the base was an important part of the US naval forces and in the months leading up to the attack, the fleet had been placed on alert due to the rising threat from Japan’s military ambitions in the area. 

In the early 1930s, Japan began a military campaign in the Pacific to increase its military presence and influence in the region. By 1941 Japan had invaded major Pacific nations such as China and Korea and was actively seizing Pacific islands rich in natural resources. These moves by the imperial forces worried President Roosevelt who saw Japan as a potential threat to US interests in the pacific. In response, the US began imposing economic sanctions on Japan to attempt to slow down its military ambitions. However, tensions escalated when Japan invaded French Indochina in September 1940, prompting the US to impose an oil embargo on Japan. This had a significant impact on Japan, as 80% of its oil was imported from the US. Japan was faced with a difficult decision, as it had only 18 months of reserves available for its imperial forces. The options were either to withdraw from China to appease the Americans, or to launch an overwhelming strike against the US pacific forces in order to prevent them from interfering with Japanese military affairs. Following the embargo Japan began to see the US as a hostile nation and began to sever diplomatic relationships.