(Monday, December 1, 1941; six days before the Japanese surprise attack on Pearl Harbor) — Japanese Emperor Hirohito approved a “war against United States, Great Britain and Holland” today during an Imperial Conference to commence with a surprise attack on the U.S. Pacific Fleet at its main forward base at Pearl Harbor in Hawaii.

On Nov. 30, 1941, Prince Takamatsu warned his brother, Hirohito, the navy felt the Empire could not fight more than two years against the United States and wished to avoid war.

But after consulting with Marquis Koichi Kido, Lord Keeper of the Privy Seal of Japan, and Prime Minister of Japan Hideki Tojo, the Emperor called Admiral Shigetaro Shimada and chief of the IJN General Staff Fleet Admiral Osami Nagano, who reassured him that war would be successful.

On Dec. 2, 1941, a radio signal containing the code words “Niitaka yama nobore” (Climb Mount Niitaka) was received by Vice-Admiral Chuichi Nagumo aboard his flagship Akagi, ordering the Japanese aircraft carrier strike force to attack Pearl Harbor on Sunday, December 7, 1941 (Monday, Dec. 8 in Tokyo).