According to President Roosevelt, why was Japan’s attack on Pearl Harbor such a surprise? Japan and the United States were looking for ways to solidify peace in the Pacific. Japan was an ally of the United States in World War II. Japan and the United States were supposed to attack China together. Japan and the United States had positive foreign relations.

The attack on Pearl Harbor was a surprise military offensive by the Imperial Japanese Navy against the United States naval base at Pearl Harbor (Hawaii) on the morning of Sunday, December 7, 1941. The attack was intended as a preventive action aimed at to avoid the intervention of the United States Pacific Fleet in the military actions that the Empire of Japan was planning to carry out in Southeast Asia against the overseas possessions of the United Kingdom, France, the Netherlands and the United States. The Japanese made this offensive coincide with the attack on the possessions of the British Empire in Hong Kong, Malaysia and Singapore, which were already in their possession in mid-February 1942.

The attack deeply shocked the American people and led directly to the entry of the United States in World War II, both in the theaters of war in Europe and the Pacific. The day after this offensive, December 8, the United States declared war on the Empire of Japan. The internal support in North America for the non-intervention in the world conflict, which had been strong, disappeared, while the clandestine assistance to the United Kingdom was replaced by a full alliance. Nazi Germany and Fascist Italy declared war on the United States on December 11, in response to operations launched against the Asian power of the Axis.