September 17, 1941 
Memorandum for the Assistant Chief of Staff, W. P. D.: 
Subject: Combat Estimate, Japan. (With map showing disposition armed 

In compliance with verbal request, this date, from the Assistant Chief of Staff, W. P. D., there is attached hereto (Tab A) a brief Combat Estimate on Japan, with a map showing the disposition of Japan's armed forces and the Asiatic area at present occupied by the Japanese.

                                                SHERMAN MILES
                                      Brigadier General, U. S. Army,
                                   Acting Assistant Chief of Staff, G-2.
   Tab A
   Map [1]

[1] Omitted.

Page 1355


Japan has an active army of about 2,000,000, including an air force of 55,000, and a trained and partly trained reserve of 3,500,000 men.

The active forces are deployed over a wide area from Karafuto and Manchoukuo in the north to the Southern French Indo-China-Thailand border in the south. The estimated number of active divisions or their equivalent is 68, plus 15 depot divisions in Japan Proper. Japan has recently mobilized approximately 500,000 reserves which have been utilized as replacements and in forming new units included in the above estimate.

Japan has been withdrawing a considerable number of her troops from China and despatching them to Indo-China and Manchuria. Some of these have been replaced by Manchurian and Wang Ching-wei's puppet troops. Since the outbreak of the Russo-German war, the forces in Manchoukuo have been increased from 8 to 21 divisions with auxiliary troops including 4 tank regiments and 4 cavalry brigades, totalling about 500,000 officers and men. The Japanese army is well trained and an efficient fighting force. Officers are well qualified to perform their various duties in peace and war. The staff has functioned well during difficult tactical operations in China. The enlisted men, although somewhat lacking in initiative, are well trained, experienced in combat, well disciplined, courageous and aggressive to the point of recklessness. The Japanese have been consistently successful in China from a tactical point of view and only combat with a modern army can determine Japan's relative efficiency compared to occidental modern armies. Japan's army is physically hardy and psychologically inspired by loyalty to the Emperor, devotion to duty and a fanatical patriotism which make it a dangerous foe on the Asian continent or nearby islands.

The Japanese Army and Navy air forces have made rapid progress since 1937. Personnel strength of Army and Navy is 55,000 officers and men and the two services have a combined plane strength of approximately 3,743 combat planes. The Army squadrons number 114 and the Navy has 124 squadrons. Plane design has lagged, but lack of formidable opposition has left them undisputed air superiority. Four years of continuous air operations have increased the efficiency of Japanese aviation no small degree. Recent acquisition of German planes and technical advisors has contributed to Japanese air proficiency.

The Japanese Army is the best equipped army in Asia. Its equipment, however, is inferior to that of any of the modern European armies. Shortage of raw materials and production capacity will limit the number of new divisions which can be organized, even though Japan's partially trained manpower is ample for her anticipated needs. Personal equipment appears to be sufficient and in good condition but there is a shortage of organization equipment such as tanks, and other mechanized equipment, antiaircraft weapons and modern artillery.


Japan has a navy consisting of approximately 180,000 men and officers exclusive of about 20,000 in the naval air corps. The naval vessels have over a million tons already built and nearly 500,000 tons in the process of building. The navy is divided into two main divisions: The Combined Fleet and the Japanese Naval Forces in China. The latter consists of the North Central and South China Fleets. The Combined Fleet is based in home waters.

The Japanese naval personnel is well trained-equal to that of the British and American navies. The Japanese navy is modern, well balanced, and ready for prompt service. It is relatively strong in aircraft carriers and tenders; it would be a formidable opponent to the navy of any power or those of any combination of powers attempting offensive operations in the western Pacific area.

Japan, because of her geographic location blocks all sea approaches, north of Saigon, to the southeastern coast of Asia; flanks all routes from the east to the eastern and northeastern coast of the mainland; and is in a remarkably strong strategical position for defense against any distant naval power. Furthermore her geographic position is such that her navy, on the strategical defensive, could from time to time successfully assume the tactical offensive.