Results of The Attack On Pearl Harbor - Germany and Italy Declare War

Germany and Italy Declare War

See also: German American internment, Italian American internment, and German-Japanese relations

On December 11, 1941, Nazi Germany and Fascist Italy declared war on the United States, and the United States reciprocated, formally entering the war in Europe.

German dictator Adolf Hitler and Italian dictator Benito Mussolini were under no obligation to declare war on the United States under the mutual defense terms of the Tripartite Pact. However, relations between the European Axis Powers and the United States had deteriorated since 1937. Earlier in 1941, the Germans learned of the U.S. military's contingency planning to get troops in Continental Europe by 1943; this was Rainbow Five, made public by sources unsympathetic to Roosevelt's New Deal, and published by the Chicago Tribune. Moreover, with Roosevelt's initiation of a Neutrality Patrol, which in fact also escorted British ships, as well as orders to U.S. Navy destroyers first to actively report U-boats, then "shoot on sight", American neutrality was honored more in the breach than observance.

Having been unaware of Japanese plans, Hitler was initially furious that the United States had been dragged into the war at a time when he had not yet acquired full control of continental Europe. Hitler, who had previously declared the Japanese "Honorary Aryans" claimed that this is what happens when your allies are not Anglo-Saxons. However, he decided war with the United States was unavoidable, and the Pearl Harbor attack, the publication of Rainbow Five, and Roosevelt's post-Pearl Harbor address, which focused on European affairs as well as the situation with Japan, probably contributed to the declaration. Hitler underestimated American military production capacity, the nation's ability to fight on two fronts, and the time his own Operation Barbarossa would require. Similarly, the Nazis may have hoped the declaration of war, a showing of solidarity with Japan, would result in closer collaboration with the Japanese in Eurasia, particularly against the Soviet Union. Regardless of Hitler's reasons, the decision was an enormous strategic blunder and allowed the United States to enter the European war in support of the United Kingdom and the Allies without much public opposition.

Author Ian Kershaw records Hitler's initial reaction to the attack, when he was first informed about it on the evening of 7 December at Führer Headquarters: "We can't lose the war at all. We now have an ally which has never been conquered in 3,000 years". Well before the attack, in 1928 Hitler had confided in the text of his then-unpublished Zweites Buch that while the Soviet Union was the most important immediate foe that the Third Reich had to defeat, the United States was the most important long-term challenge to Nazi aims.

Hitler awarded Imperial Japanese ambassador to Nazi Germany Hiroshi Ōshima the Grand Cross of the Order of the German Eagle in Gold (1st class) after the attack, praising Japan for striking hard and without first declaring war.