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Decisive Battle Doctrine

The Japanese Navy's Decisive Battle Doctrine (Kantai Kessen) was the counterpart to the American Plan Orange. The plan assumed that Japan would quickly seize control of most of the Philippines, both to neutralize the Asiatic Fleet before it could attack Japanese communications and to provoke the Americans into a hasty counterattack. It was assumed that this would take the form of a counteroffensive by the U.S. Navy across the Mandates, with the goal of relieving Manila and blockading Japan. The American Fleet would be met by the Japanese Fleet somewhere in the western Pacific for a decisive battle on the model of the battle of Tsushima in the Russo-Japanese War of 1905.

Both sides assumed a numerical superiority of  3:2 in battleships in favor of the Americans, as established by the naval disarmament treaties. Under the square law of combat effectiveness, this all but guaranteed an American victory in the final decisive battle. The Japanese therefore put heavy emphasis on attrition tactics (zengen sakusen) to weaken the American battle line during its long voyage across the Pacific. These were based on night torpedo attack by destroyers and cruisers, and, as they became more capable, aircraft

Japanese submarine strategy was largely shaped by the imperatives of attrition tactics. Japanese submarines were built with relatively high surface speed, typically 23 knots, in the belief that this would be sufficient to allow Japanese submarines to repeatedly sweep around and achieve firing position on an American force advancing at economical cruising speed. However, fleet exercises showed that the speed advantage was simply not sufficient and a submarine would get just one chance to attack any American force it made contact with. This constituted a serious flaw in the Japanese attrition strategy.

Other flaws in the Japanese strategy became evident when the Americans finally launched their counteroffensive. The islands of the central Pacific were sufficiently far apart that they were not mutually protecting, and air units in the islands were easily defeated in detail by the American carrier forces. The long-range attack bombers on which the Japanese pinned so many hopes could not be adequately escorted by fighters and proved highly vulnerable. After a near debacle at Tarawa, the Americans became proficient at neutralizing beach defenses with naval fire support, and together with the island hopping strategy, made a shambles of the Japanese perimeter. When the two fleets finally met in the Philippine Sea, it was the Americans who won the decisive victory.

Decisive Battle Doctrine became so ingrained in Japanese naval thinking that it became difficult for the Japanese to conceive of any other course for the war (Zimm 2011):

In one seminar after a joint Army-Navy wargame, an officer raised the possibility that the Americans might do something other than make a move to relieve the Philippines — for example, thay might immediately launch an attack against the Japanese mainland. Surely different eventualities should also be studied? A Naval General Staff officer supervising the maneuvers replied:

The campaign against the Philippines has already been decided on as operational policy by the imperial navy, and as such is under study in collaboration with the army. It is highly regrettable that one should hear arguments rejecting it. We must not forget that to coordinate ideas on strategy is one of the aims of these exercises.

This astonishing inflexibility in doctrine would figure prominently in the Japanese defeat in the war.

However, not all Japanese naval leaders were so inflexible. In his 7 January 1941 memorandum "Views on military preparations" (Gumbi ni kansuru shiken), Yamamoto Isoroku correctly predicted that the ascendancy of aircraft and submarines meant that the single great decisive battle would never take place, and he called for the Navy to expand its air forces and better train its commanders for the numerous small engagements that would take place instead. However, with war less than a year away, there was not enough time for Yamamoto to fully press his case and for such sweeping changes in doctrine to be made.

The Pearl Harbor attack was a major departure from Decisive Battle Doctrine. It was also an enormous gamble and a diversion of much of the Navy's striking power from the main drive into southeast Asia. Nor did the Navy General Staff believe the attack was necessary: They argued that the most likely response of an undamaged Pacific Fleet to the drive into southeast Asia would be an attack on the Marshalls, and Navy General Staff believed the Japanese Navy was well prepared to intercept such a move and deliver a crushing counterattack.

The temporary crippling of the American battle line ensured that the Americans would not stage an early drive west to relieve the Philippines. Instead, the Americans adopted a strategy of raids and local counterattacks on the Japanese perimeter that culminated in the decisive Guadalcanal campaign. By the time the Americans began the central Pacific campaign of 1943-1944, which followed the basic outline of Orange, the Japanese Navy was itself so worn down by attrition that it no longer had any hope of winning a decisive battle.

References

Evans and Peattie (1997)
Miller (1991)

Zimm (2011)



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