What did Hitler think when the Japanese attacked Pearl Harbor?

Answer 1

Hitler was happy when the Japanese attacked the United States on December 7, 1941. He rushed back to Berlin, Germany from the Eastern Front to declare War on the United States on December 11, 1941. He incorrectly assumed that the Japanese would keep the United States too busy to stop Germany in Europe. In the end, it was a mistake to declare war on the US. The United States used about 25% of its economic & military power to defeat Japan, and used the remaining 75% against Germany.

Answer 2

Hitler was surprised. The Japanese had neither consulted the Germans, nor even bothered to inform them of their plan to attack the US.

Nevertheless the Germans declared war on the US four days after the attack, and three days after the US declared war on Japan. This was the only time Germany declared war on anybody during the entire war. Usually they just invaded your country and let you figure out you were at war. But, with no shared border with the US that wasn't possible.

Under the terms of the Axis alliance Hitler was not obligated to go to war on Japan's behalf. The treaty of alliance obligated Germany to come to Japan's aid only if some other nation attacked Japan, not if Japan did the attacking. But Hitler had little regard for the US, or for president Roosevelt ("That cripple" he called him), and had been irked by US policies such as Lend-Lease, the 50 navy destroyers the US had given to Britain to fight German submarines, and the US Navy's escorting convoys of ships carrying Lend-Lease supplies to Britain as far as the mid-Atlantic, where British escorts took over. There had been an undeclared naval war in the Atlantic that fall of 1941, with US sub-chasers several times attacking and depth-charging suspected U-Boats, and one US destroyer torpedoed and sunk by the Germans, and another torpedoed and damaged with heavy loss of life.

Germany had entered into the alliance with Japan because they hoped the Japanese would go to war with Soviet Russia when the Germans did, and drub the Russians like they did in the Russo-Japanese War of 1905. But, the Japanese did not oblige. They had their own plans, but would have been happy to gather the fruits of victory from Russia's Pacific coast if the Germans had managed to finish off the Russians for them. So instead of getting help with the Soviets, the Germans got the brunt of the US war effort. 85% of America's war effort was directed at Germany until Germany was beaten. That also points up the madness of the Japanese in attacking the US - using only 15% of its strength the US was able to battle all the way across the Pacific to Japan's doorstep.