The primary cause of Pearl Harbor was Japanese Aggression. Japan, under Emperor Tojo, had formed alliances with the other two Axis powers, Germany and Italy. The belief was the the war in Europe gave a nation such as Japan the perfect element of diversion to be able to control the Pacific Island nations. While Europe was trying in desperation to stave off Hitler, the efforts were not very successful. For its part, America was firmly committed to pursing a policy of isolationism, not wanting to involve itself in the "affairs of Europe." However, privately, President Roosevelt and the government knew American entry into the war was inevitable. America had been giving support to Britain in its fight against Hitler and Mussolini with acts such as The Lend- Lease Act. Military advisers also were aware of increased Japanese aggression in the Pacific and were mindful of this, also. The Japanese, in an attempt to weaken the U.S. Navy and seize control of natural resources such as oil and rubber, and solidify their control of the Pacific Rim nations attacked American Naval Forces at Pearl Harbor, in Oahu, Hawaii on the morning of December 7, 1941.
Through an unprecedented air attack on American soil and screaming "Babe Ruth will die," Japanese bombers caught the Americans by surprise. American cryptographers were able to decipher telegraph communication between Tokyo, capital of Japan, and the Japanese Embassy in America, as well as analysis that suggested Japanese Aggression was increasing, but these warning signs were interpreted too late to prevent a staggeringly brutal attack on America. The attack on Pearl Harbor did something that all the Fireside Chats in the world could not do: It galvanized America into action. The morning after Pearl Harbor, American civilians flooded into Selective Service offices ready to serve their nation and ushered American entry into World War II. The Japanese achieved their goal of complete surprise. Yet, they ultimately paid the price for it, as American entry into the war was the decisive action that ended up spelling victory for the Allies and defeat for the Axis powers, something that was viciously felt by Japan, itself, when America dropped the Atomic Bomb on the towns of Hiroshima and Nagasaki about four years after Pearl Harbor and causing Japanese surrender.