Pearl Harbor

On 9 and 10 September, Hirohito had meetings with Hajime Sugiyama about the mobilization for the planned southern advance operation and his fears about a two-front war. Answering to the Emperor's questions about his fears "if pressure comes from the North", on the Soviet front, Sugiyama said "Once we have begun the southern operation, we cannot pay attention to anything else. We have to keep pushing forward until we achieve our objectives. Your Majesty, we need your understanding. If something happens in the north, we will transfer troops up from China but we must not stop the southern operation halfway."

Military leaders like Hideki Tojo, Sugiyama and Nagano were more willing to take military actions and by stating that the time has run out and negotiations didn't bear any fruit, while Prime Minister Fumimaro Konoe saw himself losing his argument of more negotiations and possible concessions to avert possible war. Tojo stated during the negotiation phase that

To yield to the American demand and withdraw their troops, would wipe out all the fruits of the China War, endanger Manchukuo, and jeopardize the governing of Korea. To accept troop withdrawal in name only would not benefit Japan either. Withdrawal would mean retreat. It would depress morale. A demoralized Army would be as worthless as no Army. Our troops in China are the "heart of the matter." Having made one concession after another, why should Japan now yield the "heart?" "If we concede this, what is diplomacy? It is surrender … a stain on the history of our empire!

On October 16, 1941, Fumimaro Konoe resigned and proposed prince Naruhiko Higashikuni as his successor. Higashikuni was also the choice of the Army and the Navy. Hirohito choose instead Hideki Tojo as Prime Minister of Japan since, as he told to Konoe, he was worried about having the imperial house being held responsible for a war against Occident.

On November 3, after many meetings with emperor Hirohito about the military strategy, IJN general staff Osami Nagano explained to him in detail the final version of the attack plans of Pearl Harbor. On 5 November, Hirohito approved in imperial conference the operation plan for a war against the United States, Great Britain and Holland which was scheduled at the beginning of December if no significant changes were achieved through diplomacy.

With the Hull note of November 26, 1941, Japan's leaders decided not to cancel the Pearl Harbor attack, in planning for 10 months and in serious training for most of the year. The fleet had been assembling in the Kuriles, and indeed sailed the day the Hull note was sent. US and UK demands to back down from its actions in China, at the exclusion of Manchukuo and French Indochina, were seen as meaning a loss of international prestige for Japan, "losing face," losing national pride, and most of all losing everything gained in the Second Sino-Japanese war and losing access to oil, despite the heavy investments in the military and the five year war with China.

On 30 November 1941, prince Nobuhito Takamatsu warned his brother Hirohito that the Navy felt the Empire could not fight more than two years against United States and wished to avoid war. After consulting with Koichi Kido(who advised him to take his time until he was convinced) and Tojo, the emperor then called Shimada and Nagano who reassured him that the war would be successful. On December 1, Hirohito finally sanctioned a "war against United States, Great Britain and Holland" in another imperial conference.