On 25 September 1943, Imperial General Headquarters drew a line that included the Kurile Islands, Ogasawara Islands, Mariana Islands, Caroline Islands, western New Guinea, and the Sunda Islands to Burma. This area was labeled the Absolute National Defense Zone. The new defensive perimeter thus excluded the Marshall Islands, the Solomon Islands, and eastern New Guinea. The army and navy General Staffs planned to reorganize and build up the military and naval forces inside the zone for a future decisive battle with U.S. forces.
On 30 September, the plan was officially declared in effect during a meeting at which Emperor Hirohito was in attendance. The plan called for the following: (1) establish an Absolute National Defense Zone to meet an Allied counteroffensive; (2) improve relations with the Soviet Union; (3) bring the war in China to a victorious conclusion; (4) strengthen relations with Germany; (5) educate the peoples of Japanese-occupied areas and develop the Greater East Asia Co-prosperity Sphere; (6) reorganize the nation for total war; and (7) intensify propaganda against the Allies.
Despite this plan, the Japanese army continued to be preoccupied with China to the detriment of the defense of the Pacific islands, and the navy persisted in holding Truk Island in the central Pacific, which was outside the defense zone. The failure of the army and navy to reach complete consensus regarding the defense zone was of considerable benefit to the Allies in 1944 and 1945.
Evans, David, and Mark Peattie. Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887–1941. Annapolis, MD: Naval Institute Press, 1997.; Kirby, Woodburn. The War against Japan. Vol. 3. London: Her Majesty's Stationery Office, 1958.; Van der Vat, Dan. The Pacific Campaign. New York: Touchstone, 1991.