*** World War II : Imperial Japanese Navy

World War II: The Imperial Japanese Navy (1941)

Figure 1.--

Conspiracy theorists make the absurd charge that President Rooiselvelt and Secretary of War Marshall were responsible for the debacle at Pearl Harbor. Unsaid is the racist assumption that the Japanese on their own could not hsve carried out such a devestating attack. The simple truth, however, is that in 1941 the Japanese had the most powerful naval fiorce in the world. Not only did the Japanese have more carriers and carrier aircraft, their planes were superior to American and British carrier aircraft. (the British were still uding biplanes), And the Japanese pilots were better trained and more exoperienced. The real question is not how the Japanese succeeded at Pearl Harbor, but how the U.S. Navy managed to stop the Japanese only 6 months after Peal Harbor before American industry could provide the stream of plsanes and ships that would eventually destroy the Imperial Navy.

Japanese Strategic Concepts

The Japanese faced a quandry. They had achieved sucess after success in China, but still the war dragged on. The war in China put substantial demands on the Japanese economy. To make matters worse, their primary source of resources to conduct the war in China as the United States. This was especially true of petroleum. Japan would have to end the war in China or find alternative supplies of natural resources. German successes in Europe opened up the prospects of seizing the resource rich British, Dutch, and French colonies in Southeast Asia. But situated between the Home Island and those resources were the American Phillipine Islands and the implied threat threat of the Pacific Fleet which President Roosevelt had moved forward to Pearl Harbor. One of the not yet fully inderstood questions of World War II is why the Japanese did nor strike north at the Siviets after the Germans had destroyed much of the Red Army. Once the Japanese had decided on war with America. Their focus became the Pacific Fleet at Pearl Harbor. The Japanese strategic concept was to smash the Pacific Fleet and seize a huge empire with the resources it needed and then fortify it so that it would be enormously costly for the Americans to retake. The resources from the empire which the Japanese called the Greater East Asia Co-Prosperity Sphere were to be used to support the Japanese military. The Japanese with little knowledge of America were convinved that America would never make the sacrifices needed to retake the Japanese conquests. This strategic concept was fataly flawed. First, the attack on Pearl Harbor was a starteling military success, but a strategic blunder of incalcuable proportions. The attack turned a biterly divided America into a unified, mortal enemy. Second, the Japanese strategy had no provision for attacking the industrial base of the United States, an industrial base far exceeding the industrial capacity of Japan. This industrial base allowed American to build a military force that Japan could not possibly match. Third, the Japanese were unprepared for the American submarine campaign, a campaign which by 1943 was beginning to deny Japanese industry the resources from their newly won empire. The Japanese found their army bogged down in unwinnable campaigns in China and Burma and morooned on isolated Pacific islands that they could no longer supply or even defend. Nor could the resources of their empire be brought back to the factories on the Home Island. Japan at the time of its surrender in 1945 was approaching starvation.

Japananese Naval Policy

The major powers after World War I chastened by the incredible loss of life and destruction persued a policy of naval disarmament. The Treaties of Washington (1920) and London (1930) limited national fleets. Interestingly, Admiral Yamamoto suggested that battleships be scsrapped. I am not sure what the Japanese onjective was with this proposal. It was not taken seriously by the other naval powers. One result was that the Japanese began to take an interest in carrier which were not covered by the treaties. A naval building program was persued in viloation of the treaties, although I am not sure when this begun. Certianly the construction of Mustashi? and Yamato far exceeded the limitations (1937). The Japanese Navy was disturbed that the Japanese did not receive parity with the American and British fleet. Many advocated an aggressive preparation for war. Others such as Admiral Isoroku Yamamoto insisted that war with America and Britian would be suicidal because of their superioir industrial and technical capaboility. Yamaoto was for a time targeted for assasination. He was, however, appointed commander of the Imperial Navy. He was an inovative strategist and in particular propmoted the naval air wing.

Third Naval Replenishment Program (1937)

Somw of Japan's most powerful ships were built as a result of the Third Naval Replenishment Program. Gicen the time required to build major naval vessels. This was the last major ship building program bgan by the Japanese to deliver capital ships to the Imperial Navy during the Paciufic War. Carriers Zuikaku and Shokaku were added to the fleet and participated in the Pearl Harbor attack. Both damaged in the Coral Sea engagement were not a Midway. Also authorized were the giant battleships Yamoto and Musashi. These ships were designed without treary restructions, they were built with the idea of having no foreign rival. As it turned out, both Zuikaku and Shokaku were outclassed by the American Essex clas carriers and a new generation of powerful American aircraft. Yamoto and Musashi spent most of the war as obsolete hulks, hising from American submarine and carriers.

The Japanese Army

Admiral Yamamoto and many other, but not all, naval officers appreciated the industrial potential of America and were notanxious to launch a naval war in the Pacific. As a result, Yamamoto had to be guarded and careful of his movements outside of naval bases. Japanese Army commanders had no such apprecition for the potential power of America. They saw a country trying to avoid war and onterpreted it as evidence of the weakness of the Ametican character. In addition, the Japanese Army dominated by the Strike North Faction fought an undeclared war with the Soviets along the Manchurian-Mongolian border (July 1939). The superior industrial output of the soviet Union produced artillery and tanks that outclassed Japanese weaponry. The Japanese Army suffered substantial losses and, as a result, were not anxious to pursue another campaign against the Soviets. Amazingly, the defeat at the hands of the Soviets, did not cause the Japanese militrists to rethink their commitment to military aggression, only to change targets. The Strike South Faction in the Imperial Army began looking at America, an even greater industrial power, and the only country in 1941 capable of conducting war on a global scale. This has to be the greatest strategic blunder in the history of warfare. (Of course the American military for its part badly underestimate theccapabilitues of the Japanese.) American support for China caused Army officers to advocate a war with America. Many in the Army had convinced themselves that fighting spirit could over come American industrial superiority. As the British were engaged in Europe and France and the Netherlands occupied, their colonies with key natural resources needed by resource-poor Japan seem easy prey. The only other creditable force in the Pacific was the American Pacific Fleet at Pearl Harbor. The Army in 1941 dominated the Japanese Government and thus the Imperial Navy would have to acceed to decisions made by the Army leadership.

The Imperial Navy (1941)

The Japanese Imperial Navy (Nihon Kaigun) by 1941 was the dominant naval force in the Pacific. The Japanese had a large well-trained navy with excellent ships. There was no peace-time neglect as the British and U.S. navies experienced. The American Navy was aware that the Japanese had a modern effective navy, but did not fully understand the capabilities of the Imperal Navy or the danger posed by the sizeable carrier fleet. The Japanese Imperial fleet was superbly trained with outstanding night fighting capabilities. Not only was the fleet well trained and included modern vessels, many of the Japanese vessels and naval aircraft were superior to American and British vessels in many aspects. Japan led the world in operational aircraft carriers and carrier aircraft. (The British in 1941 were still using Swordfish biplanes on their carriers and American planes, especially the fighters were slower and less manuerable. The Japanese Mitsubishi Type 00 fighter, the Zero, was both faster and more maneuverable than either the U.S. Navy carrier fighter, the Grumman F4F Wildcat. The full extent of the threat was in part obscured by American racial sterotypes and wide-spread belief that the Imperial Navy was not an effective force. In reterospect, the only suprising question about the attack on Pear Harbor and Japanese offensive in the South Pacific, is not how they succedded, but how America managed to stop the Japanese after only 6 months of victories. The two glaring weakeneses were the lack of radar and the ineffective fire supression systems. Not well understood is that Japan had a very substantial submarine fleet.

Japanese Naval Forces

Japans superbly trained carrier force with its Zero fighters threatened to totally destroy the Pacific fleet in the early months of the War. The Imperial fleet also included thectwo largest battle ships of the War, Yamato and Musake> One of the greatest strengths of the Imperial Navy was its superb cruisers and crews trained for night fighting. They proved extremely effective before radar was fully implemented by the U.S. Navy. Japanese destroyers also proved very effective, but like other Imperial Navy vessels were forced to fight at axdusadvantage without radar. The greatest disappointment of the Imperial Navy was its substantial submarine force. Not only were the Japanese subs poorly constructed, but Jaoanese naval doctrine was flawed.

Japanese Carrier Force (1941)

Japan in 1941 had a massive superiority in carrier forces. The extent of this superiority and importance was before Pearl Harbor not fully appreciated by the U.S. Navy and the Royal Navy. Nor did many Japanese naval commanders fully appreciate it. The Japanese superiority was staggering. The Imperial Navy's was composed 10 aircraft carriers and 1,500 superbly trained aviators. Japan not only possesed the most carriers, but the most effective carrier-based fighter (the Zero) and the best trained and most experienced pilots. The Imperial Navy, partly because of the Wasington Treaty limitations, had been a pioneer in naval aviation. The Imperial Navy built the first carrier designed to be a carrier from keel-up, the Hosho. The Imperial Navy during the 1920s and 30s placed great emphasis on naval aviation. The fleet carrier arm was impressive. It consisted of six large carriers and several more light carriers, Akagi Class: Akagi (1927). Kaga Class: Kaga (1928). Ryujo Class: Ryujo (1931). Shokaku Class: Shokaku (1941) and Zuikaku (1941). Soryu Class: Soryu (1937) and Hiryu (1939). Taiyo Class: Taiyo (1941). The Japanese, largely under the leadership of Admiral Yamamoto, gave primacy to their carrier force and grouped the most powerful naval force in the world--the First Air Fleet. This was a policy to the German Pazer formations, the carriers were grouped together rather than dispersed thrughout the fleet. The Japanese were not only numerically superior, but entirely unappreciated by the U,S. Navy was the competence of the Japanese aviators. The Japanese had a rigorous pilot training program which produced the most skilled naval aviators--although the program was a lengthy demanding one. The combination od highly traied avitors and a first class, modern plane proved a devestating combination.


The Imperial Navy, like other World War II navies, still attached considerable importance to big-gun battleships (戦艦 Senkan). As part of thar doctrine, they decided to build two super bttleships--Yamato and its sister ship Musashi . These wee the largest battleships with the heaviest armament ever built. They were not reeady for nattle until after Japan launched the war and even them the Japanese held these ships back for prestige reasons. Many of the Japanese battleships were older ships. nd the lack of radar put them at a significant disadvantage. The Japanese battleships did not play an important role in the War until the American landings on Guadalcanal opend the South Pacific campaign. The Japanese used their battleships and cruisers to try to knockout Henderson Field, but had to do it at night because of the possibility of air attack during the day. As terrific naval battles were fought around Guadalcanal, the Japanese began to lose battleships. Enterprise air groups sank Hiei and American battleships sank Kirishima in a rare battleship to battleship duel durng the naval Battle of Guadalcanal (November 15, 1942). This and damage to the carriers convinced th Japanese to withdraw the Imperial Fleeet fom the south Pacific. It was not until the U.S. Navy approched the Marianas that the Imperial fleet deployed agin for a major battke. The Japanese battleships did not play an important, but they did in the subsequent Battle of Leyte Gulf (October 1944). Rear Admiral Jesse Oldendorf of the U.S. 7th Fleet attacked the Japanese southern force destroyed Yamashiro and Fusō in the Surigao Strait. Then air groups attacked the Central Force, sinking Musashi . Vice Admiral Takeo Kurita commanding the Center Force turned his force back toward Leyte Gulf. It still included Yamato, Kongō, Haruna, and Nagato and their cruiser escorts, but again turned away because of an incredibly small force of American destroyers and escort carriers. The last important naval action of the war was a kamikaze attack by Yamato off Okinawa (April 1945).



Japan began the Pacific War with the fiest destroyersc fleet in the world. Modern design, combined with marvelouslt trained crews and the long-lance torpedo. It was a deadly combination. It was a formidable force to recon with and not matched by the American Pacific fleet until the Fletcher-lass destoyers began to arrive. As was the case in other areas. The Americans an British were uawarev of the leathality of the Japanese destoyers until after Pearl Harbor and surfce engagements began. Ship and weeapon designwas at the cutting edhe of technology and the long-lnce torpedo was far superior to anything in the Allied asrsenl. This was important because the torpedo is the destroyer with its small guns, its major weapon. Disgracefully, ASmerican tiorpedoes oftenm did not work. The Japanese were esopecially skilled in nigh-fighting. The Japanese worked extensively on ship design, until what they referred to as 'Special Type' was adopted as a standard design (1937). The resulting Japanese destoyers were lrger asnd more powerful than the Allied (Anmericam=, British, and Dutch destoyers they faced. Thiswas soon apparent in the disaterous results in the Java Sea (February 1942). It at first thought that the Japanese only suceeded at Pearl Harbor because it was aneak artack. It should became apparent that the Allies faced a foormidable naval force. The potential of the Japanese destroyers were sjown at Tassafaronga (November 1942). After this the American force began to grind down the Japanesec destoyers. This would have been an important contribution to a Japanesevivtoiry had the Pacific War been a short one as they had expected. But it was not. Imprtant factors for the Japanese included included 1) loss of air protection, 2) ineffective anti-aircraft armament, 3) ineffective anti-submarine weaponry. 4) poor radar, 5) overly aggressiveness tactics, 6) diversion for dangerous supply missions to Guadalcanal and other islands in the Solomons. 【Evans and Peattie】 On the American side, factors inckluded: 1) Flether-class destoyers, 2) greatly increased numbers, 3) more exoerienced crews, 4) increasingly effectiuve radar, 4) expanding air power, 5) torpedies that worked, and 6) increasingly aggrsive submarne operations. Allm ofvthis changed the dymamic of destroyer operations. Adm. Arleigh Burke was at the vforefront of the Pacific Fleets evolving destroyer operations. The Jaoanese launced the Pacific War withb 68 front-line Special Type destroyers. An additional 64 were added durung the war. More than half of this fleet was lost before late-1943 in heavy surface actions in the Solomons. The Imperial Navy was unprepared for American submarines armed with torpedoes that actually exploded. Japanese interests were in large destou=yers that coukd play an imprtantv role in a major surface action. And Japan unlike the Americans did not launch small escort destoyers that could be used for convoy escorts. As a result,. Japanese war factories were cut off from the ra materils they needed, largely by American sumarines. Japan was also cut off from needed food imports. Only 31 Japabnese destroyers survived the War. 【Whitley, pp. 187–208.】


The Japanese Navy got its first submarines from the United States, buying them from the Electric Boat Company in the early 20th century. More sophisticated submarines were obtained as part of the World War I peace settlement. The Allies gave thge Japanese a number of German U-boats. After the War, the Japanese Navy began to focus on the American Navy as its most likely future opponent. The Japanese began building an advanced sibmarine, the I-class submarines. This submarine reflected the empire that Japan began to conceive in Southeast Asia and the Pacific. The I-boats were very large submarines, reflecting the vast distances involved in Pacific operations. The I-class were 350 ft long and had rangds of 20,000 miles, more than twice that of 7,000-8,000 mile range of the German U-boats. The Japanese had smaller subs for coastal patrol, but the backbone of the fleet was the I-class boats. Surprisingly the sunstantial Japanese submarine fleet had little impact on the Pacific campaign. Unlike the Americans, the Japanese began the War with the effective Type 93 Long-Lance Torpedo. The Japanese Navy never used their submarines to interdict American supply vessels. Rather they were used to target fighting ships with only limited success because of their tactical deployment. The Japanese used theor submarines as scouts and to targer warships. As the American offensive moved toward the Home Islands, the Japanese used their submarines to supply bypassed island garisons, some of which were near starvation. They were also used to supply bypassed islasnd bases where garrisons were close to starvation. They also managed to get some secret German military technology to Japan late in the war (1944). The Japanese developed especially large sunmarines that could carry a few planes. They were planning an attack on the Panama Canal until the sumarines were redeployed to defend Okinawa (1945).


There were limititations that the Japanese did not appreciate. U.S. Navy code breakers were in the process of cracking the Imperial Navy's code. This was especially important in carrier warfare because the first side to locate and strike at the opposing carriers had the best chance of success. Also the Japanese did not have radar. Because of the Japanese focus on ofense, reklarively little attention was devioted to fire supression and damage control. Despite the Imperial Navy's superority, these factors would lead to disaster 6 months after Pearl Harbor.

Commitment to War

To this day, Japanese historians often say that the United States forced Japan into World War II. Some even claim that the America tricked Japan into attacking Pearl Harbor. This is of course simply not true. Japan decided on war in the 1930s. There was a battle for power between the treaty forces seeking a peacefuil role in the world and thev militarists who saw Japan's future as being achieved through force. By the early 1930s the militaristrs had prevailed. Japan chosen war as an instrument of national policy years before Pearl Harbor and any American sanctions. Japan invaded Manchuria (1931) and China (1937), not to mention the Sioviet Union (1939). Japan also renounced the Washington Naval Treaties (1934). Even by 1941, America did not force Japan to make war. America was making no demands like the NAZIs made on Czechoslovakia or Poland. America was demanding that Japan stop its invasion of China and expansion into Southeast Asia. Japan was not forced to make war, it chose to do so.

The Pacific War

It was the Japanese carrier attack on Pearl Harbor that brought America into the War. The Japanese Imperial Fleet was a superbly trained force with modern, well designed vessels. Many did not fully appreciate the effectivness of the Imperial Navy. The lack of radar, however, proved a huge disadvantage. Allied radar and many other technical advances were the result of close cooperation between American and British scientists anf joint development projects that began even before America entered the War. There was no comparable Axis technical cooperation or even coordination of military campaigns. The Kriegsmarine had very effective radar on its surface ships like Bismarck yet advanced German technology like radar, jet engines, and other equipment was not provided to the Japanese until very late in the War, too late to be of any effectiveuse to the Japanese war effort. While Pearl Harbor was a stunning tactical victory, it was a strategic blunder by the Japanese of incaluable proportions. The Jpanes were able to seize much of Southeast Asia, but the stunning American carrier victory at Midway, significantly reduced the strike capability of the Imperial Navy. This provided the time for American industrial capacity to reated a naval force with which Japan's limited industrial capacity could not cope. While the German submarine campaign in the North Atlantic failed, the American submarine campaign in thePacific proved spectacularly successful. The Japanese merchant marine was almost completely destroying, cutting the country's war industries off from supplies and bringing the country close to starvation. Amercan industrial strength enabled America to build a naval force capable of leap froging from island to island. The Navy by 1944 had seized islands from which the Japanese Home Island could be bombed. The Navy also enabled the Army to retake tNe Guinea and the Phillipines and by 1945 Okinawa. Naval and Army forced were preparing for a full-scale amphibious invasion of the Home Islands when two atomic boms were dropped (August 1945) and Japan finally surrendered (September 1945).


Evans, David C. and Mark R. Peattie. Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887–1941 (Annapolis, Md.: Naval Institute Press, 1997), 663p.

Schom, Alan. The Eagle and the Rising Sun: The Japanese-American War 1941-1943 (Norton, 2003).

Stille, Mark E. The Imperial Japanese Navy: In the Pacific War (2014), 400p.

Whitley, M.J. Destroyers of World War Two: An International Encyclopedia. (London: Arms and Armour Press, 2000.


Navigate the CIH Worl War II Section:
[Return to Main World War II naval campaign page]
[Return to Main Japanese Navy page]
[Biographies] [Campaigns] [Children] [Countries] [Deciding factors] [Diplomacy] [Geo-political crisis] [Economics] [Home front] [Intelligence]
[POWs] [Resistance] [Race] [Refugees] [Technology] [Totalitarian powers]
[Bibliographies] [Contributions] [FAQs] [Images] [Links] [Registration] [Tools]
[Return to Main World War II page]
[Return to Main war essay page]
[Return to CIH Home page]

Created: 1:31 AM 11/15/2004
Last updated: 5:04 AM 1/9/2024