Imperial Japanese Navy

2007 Schools Wikipedia Selection. Related subjects: Military History and War

Imperial Japanese Navy (IJN) 大日本帝國海軍 (Dai-Nippon Teikoku Kaigun)
Ensign of the Imperial Japanese Navy and Japan Maritime Self-Defense Force.
Active	1869- 1947
Country	Empire of Japan
Allegiance	Empire of Japan
Type	Navy
Battles/wars	Sino-Japanese War Russo-Japanese War World War I World War II
Commanders
Notable commanders	Isoroku Yamamoto, Togo Heihachiro, Hiroyasu Fushimi and many others.

The Imperial Japanese Navy (IJN) ( Kyūjitai: 大日本帝國海軍 Shinjitai: 大日本帝国海軍 Dai-Nippon Teikoku Kaigun  or 日本海軍 Nippon Kaigun) or sometimes referred to as the Japanese Navy or Combined Fleet was the Navy of Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes. It was the third largest navy in the world by 1920 behind United States Navy and Royal Navy, and perhaps the most modern at the brink of World War II. It was supported by Imperial Japanese Navy Air Service for aircraft and airstrike operation from the fleet.

The origins of the Imperial Japanese Navy trace back to early interactions with nations on the Asian continent, beginning in the early medieval period and reaching a peak of activity during the 16th and 17th centuries at a time of cultural exchange with European powers during the Age of Discovery. After two centuries of stagnation during the country's ensuing seclusion policy under the shoguns of the Edo period, Japan's Navy was comparatively backward when the country was forced open to trade by American intervention in 1854. This eventually led to the Meiji Restoration, a period of frantic modernization and industrialization accompanied by the re-ascendance of the emperor. The navy's history of successes, sometimes against much more powerful foes as in the 1895 Sino-Japanese war and the 1905 Russo-Japanese War, ended in almost complete annihilation during the concluding days of World War II. The IJN was officially dissolved in 1945.

Origins

Japan has a long history of naval interaction with the Asian continent, involving transportation of troops between Korea and Japan, starting at least with the beginning of the Kofun period in the 3rd century.

Following the attempts at Mongol invasions of Japan by Kubilai Khan in 1281, Japanese " Wakō" pirates became very active in plundering the coast of the Chinese Empire.

Japan undertook major naval building efforts in the 16th century, during the Warring States period, when feudal rulers vying for supremacy built vast coastal navies of several hundred ships. Around that time, Japan may have developed one of the first ironclad warships, when Oda Nobunaga, a Japanese daimyo, had six iron-covered Oatakebune made in 1576.

During the Japanese invasion of Korea (1592-1598), a navy of about 700 ships and manned by 10,000 sailors was organized by Toyotomi Hideyoshi for the transportation and support of a land force of about 160,000. The transportation ships were subject to the attacks of the powerful Joseon Dynasty navy. The Japanese Navy suffered a series of defeats, at the hands of Korean Admiral Yi Sun-sin, using turtle ships, or Geobukson. After re-organizing the Navy, Japan won an engagement against Admiral Won Kyun of the Joseon Dynasty navy, and several skirmishes against Admirals Yi Eok Ki and Choi Ho of the Ming China navy. The sea route between the Japanese mainland and the Korean south coast was maintained by the activity of the navy throughout the campaign, allowing for the circulation of men and goods.

Japan built her first large ocean-going warships in the beginning of the 17th century, following contacts with the Western nations during the Nanban trade period. In 1613, the Daimyo of Sendai, in agreement with the Tokugawa Bakufu, built Date Maru, a 500 ton galleon-type ship that transported the Japanese embassy of Hasekura Tsunenaga to the Americas, which then continued to Europe. From 1604, about 350 Red seal ships, usually armed and incorporating some Western technologies, were also commissioned by the Bakufu, mainly for Southeast Asian trade.

From 1640, Japan chose the policy of Sakoku (seclusion), which forbade contacts with the West, eradicated Christianity, and prohibited the construction of ocean-going ships on pain of death.

The study of Western shipbuilding techniques resumed in the 1840s during the Late Tokugawa shogunate ("Bakumatsu"). In 1853 and 1854, U.S. Navy Commodore Matthew Perry made a demonstration of force with the newest steam warships of the U.S. Navy. Perry finally obtained the opening of the country to international trade through the 1854 Convention of Kanagawa. This was soon followed by the 1858 " unequal" U.S.-Japan Treaty of Amity and Commerce, which allowed the establishment of foreign concessions, extra-territoriality for foreigners, and minimal import taxes for foreign goods.

As soon as Japan agreed to open up to foreign influence, the Tokugawa shogun government initiated an active policy of assimilation of Western naval technologies. In 1855, with Dutch assistance, the Shogunate acquired its first steam warship, the Kankō Maru, which was used for training, and established the Nagasaki Naval Training Centre. In 1857, it acquired its first screw-driven steam warship, the Kanrin Maru. Naval students were sent to study in Western naval schools for several years, such as the future Admiral Takeaki Enomoto (who studied in the Netherlands from 1862–1867), starting a tradition of foreign-educated future leaders such as Admirals Heihachiro Togo and, later, Isoroku Yamamoto. In 1865, the French naval engineer Léonce Verny was hired to build Japan's first modern naval arsenals, at Yokosuka and Nagasaki.

By the end of the Tokugawa shogunate in 1867, the Tokugawa navy was already the largest of Eastern Asia, organized around eight Western-style steam warships and the flagship Kaiyō Maru, which were used against pro-imperial forces during the Boshin War, under the command of Admiral Enomoto. The conflict culminated with the Naval Battle of Hakodate in 1869, Japan's first large-scale modern naval battle, and ended with the defeat of the last Tokugawa forces and the restoration of Imperial rule.

Creation of the Imperial Japanese Navy (1869)

From 1868, the restored Meiji Emperor continued with reforms to industrialize and militarize Japan to prevent the United States and European powers from overwhelming her. On 17 January 1868, the Ministry of Military Affairs (also known as the Army-Navy Ministry) was established, with Iwakura Tomomi, Shimazu Tadayoshi and Prince Komatsu Yoshiakira as the First Secretaries. On 26 March 1868, the first Naval Review was held in Japan (in Osaka Bay), with 6 ships from the private domainal navies of Saga, Chōshū, Satsuma, Kurume, Kumamoto and Hiroshima participating. The total tonnage of these ships was 2252 tons, which was far smaller than the tonnage of the single foreign vessel (from the French Navy) that also participated. The following year, in July 1869, the Imperial Japanese Navy was formally established, two months after the last combat of the Boshin War.

In 1871, the private domainal navies were abolished, and their 11 ships were added to the 7 surviving vessels of the defunct Tokugawa bakufu navy to form the core of the new Imperial Japanese Navy. In 1872, the Ministry of Military Affairs was replaced by a separate Army Ministry and Navy Ministry. In October 1873, Katsu Kaishu became Navy Minister. The new government drafted an ambitious plan to create a Navy with 200 ships organized into 10 fleets. It was abandoned within a year due to lack of resources. Domestic rebellions, especially the Satsuma Rebellion (1877) forced the government to focus on land warfare. Naval policy, expressed by the slogan Shusei Kokubō (Jp:守勢国防, lit. "Static Defense"), focused on coastal defenses, a standing army, and a coastal Navy, leading to a military organization under the Rikushu Kaijū (Jp:陸主海従, Army first, Navy second) principle.

British support

During the 1870s and 1880s, the Imperial Japanese Navy remained an essentially coastal defense force, although the Meiji government continued to modernize it. The Jho Sho Maru (soon renamed Ryūjō Maru) commissioned by Thomas Glover was launched at Aberdeen, Scotland on March 27, 1869. In 1870, an Imperial decree determined that Britain's Royal Navy should be the model for development. Ships such as the Fusō, Kongō and the Hiei were built in British shipyards specifically for the Imperial Japanese Navy. A British naval mission visited Japan in 1873, headed by Comdr. Archibald Douglas. Later, Comdr. L.P. Willan was hired in 1879 to train naval cadets. Private construction companies such as Ishikawajima and Kawasaki also emerged around this time.

Two large warships were ordered from British shipyards. Naniwa and the Takachiho were 3,650 ton ships. They were capable of speeds up to 18 knots (33 km/h) and were armed with 2 to 3-inch deck armor and two 10.2-in (260 mm) Krupp guns. The naval architect Sasō Sachū designed these on the line of the Elswick class of protected cruisers but with superior specifications. An arms race was taking place with China however, who equipped herself with two huge German battleships of 7,335 tons ( Ting Yüan and Chen-Yüan). Unable to confront the Chinese fleet with only two modern cruisers, Japan resorted to French assistance to build a large, modern fleet which could prevail in the upcoming conflict.

Influence of the French "Jeune Ecole" (1880s)

During the 1880s, France took the lead in influence, due to its " Jeune Ecole" ("Young school") doctrine favoring small, fast warships, especially cruisers and torpedo boats, against bigger units. The Meiji government issued its First Naval Expansion bill in 1882, requiring the construction of 48 warships, of which 22 were to be torpedo boats. The naval successes of the French Navy against China in the Sino-French War of 1883–85 seemed to validate the potential of torpedo boats, an approach which was also attractive to the limited resources of Japan. In 1885, the new Navy slogan became Kaikoku Nippon (Jp:海国日本, lit. "Maritime Japan").

In 1886, the leading French Navy engineer Emile Bertin was hired for four years to reinforce the Japanese Navy and to direct the construction of the arsenals of Kure and Sasebo. He developed the Sanseikan class of cruisers; 3 units featuring a single powerful main gun, the 12.6 in (320 mm) Canet gun. Altogether, Bertin supervised the building of more than twenty units. They helped establish the first true modern naval force of Japan. It allowed Japan to achieve mastery in the building of large units, since some of the ships were imported, and some others were built domestically at the arsenal of Yokosuka:

• 3 cruisers: the 4,700 ton Matsushima and Itsukushima, built in France, and the Hashidate, built at Yokosuka.
• 3 coastal warships of 4,278 tons.
• 2 small cruisers: the Chiyoda, a small cruiser of 2,439 tons built in Britain, and the Yaeyama, 1800 tons, built at Yokosuka.
• 1 frigate, the 1600 tons Takao, built at Yokosuka.
• 1 destroyer: the 726 tons Chishima, built in France.
• 16 torpedo boats of 54 tons each, built in France by the Companie du Creusot in 1888, and assembled in Japan.

This period also allowed Japan "to embrace the revolutionary new technologies embodied in torpedoes, torpedo-boats and mines, of which the French at the time were probably the world's best exponents" (Howe, p281). Japan acquired its first torpedoes in 1884, and established a "Torpedo Training Centre" at Yokosuka in 1886.

These ships were the last major orders placed with France. Japan turned again to Britain, with the order of a revolutionary torpedo boat, the 1887 Kotaka, which is considered the first ever effective design of a destroyer (Evans Kaigun, p17), and with the purchase of the Yoshino, built at the Armstrong works in Elswick, Newcastle upon Tyne, the fastest cruiser in the world at the time of her launch in 1892.

Sino-Japanese War (1894-1895)

Japan continued the modernization of its navy, especially as China was also building a powerful modern fleet with foreign, especially German, assistance, and the pressure was building between the two countries to take control of Korea. The Sino-Japanese war was officially declared on August 1, 1894, though some naval fighting had already taken place.

The Japanese navy devastated Qing's Beiyang Fleet off the mouth of the Yalu River at the Battle of Yalu River on September 17, 1894, in which the Chinese fleet lost 8 out of 12 warships. Although Japan turned out victorious, the two large German-made battleships of the Chinese Navy remained almost impervious to Japanese guns, highlighting the need for bigger capital ships in the Japanese Navy (the Ting Yuan was finally sunk by torpedoes, and the Chen-Yuan was captured with little damage). The next step of the Imperial Japanese Navy's expansion would thus involve a combination of heavily armed large warships, with smaller and innovative offensive units permitting aggressive tactics.

As a result of the conflict, under the Treaty of Shimonoseki (April 17th, 1895), Taiwan and the Pescadores Islands were transferred to Japan. The Imperial Japanese Navy took possession of the island and quelled opposition movements between March to October 1895, and the islands continued to be a Japanese colony until 1945. Japan also obtained the Liaodong Peninsula, although she was forced by Russia to return it to China, only to see Russia take possession of it soon after.

The Imperial Japanese Navy further intervened in China in 1900, by participating together with Western Powers to the suppression of the Chinese Boxer Rebellion. The Navy supplied the largest number of warships (18, out of a total of 50 warships), and delivered the largest contingent of Army and Navy troops among the intervening nations (20,840 soldiers, out of total of 54,000).

Russo-Japanese War (1904-1905)

Following the Sino-Japanese War, and the humiliation of the forced return of the Liaotung peninsula to China under Russian pressure (the " Triple Intervention"), Japan began to build up its military strength in preparation for further confrontations. Japan promulgated a ten-year naval build-up program, under the slogan "Perseverance and determination" (Jp:臥薪嘗胆, Gashinshōtan), in which it commissioned 109 warships, for a total of 200,000 tons, and increased its Navy personnel from 15,100 to 40,800. The new fleet consisted of:

• 6 battleships (all British-made)
• 8 armored cruisers (4 British, 2 Italian, 1 German, and 1 French-made)
• 9 cruisers (5 Japanese, 2 British and 2 US-made)
• 24 destroyers (16 British and 8 Japanese-made)
• 63 torpedo boats (26 German, 10 British, 17 French, and 10 Japanese-made)

One of these battleships, Mikasa, the most advanced ship of her time, was ordered from the Vickers shipyard in the United Kingdom at the end of 1898, for delivery to Japan in 1902. Commercial shipbuilding in Japan was exhibited by construction of the twin screw steamer Aki-Maru, built for Nippon Yusen Kaisha by the Mitsubishi Dockyard & Engine Works, Nagasaki. The imperial Japanese cruiser Chitose was built at the Union Iron Works in San Francisco, California.

These dispositions culminated with the Russo-Japanese War (1904–1905). At the Battle of Tsushima, Admiral Togo onboard Mikasa led the combined Japanese fleet into what has been called "the most decisive naval battle in history". The Russian fleet was almost completely annihilated: out of 38 Russian ships, 21 were sunk, 7 captured, 6 disarmed, 4,545 Russian servicemen died and 6,106 were taken prisoner. On the other hand, the Japanese only lost 116 men and 3 torpedo boats. These victories broke Russian strength in East Asia, and triggered waves of mutinies in the Russian Navy at Sevastopol, Vladivostok and Kronstadt, peaking in June with the Battleship Potemkin uprising, thereby contributing to the Russian Revolution of 1905.

During the Russo-Japanese war, Japan also made frantic efforts to have a fleet of submarines. Submarines had only recently become operational military engines, and were considered to be special weapons of considerable potential. The Imperial Japanese Navy acquired its first submarines in 1905 from the United States Electric Boat Company, barely four years after the U.S. Navy had commissioned its own first submarine, USS Holland. The ships were Holland designs. They were shipped in kit to Japan and then assembled at the Yokosuka Naval Yard, to become hulls No1 through 5, and became operational at the end of 1905.

Towards an autonomous national Navy

Japan continued in its efforts to build up a strong national naval industry. Following a strategy of "Copy, improve, innovate", foreign ships of various designs were usually analysed in depth, their specifications often improved on, and then were purchased in pairs so as to organize comparative testing and improvements. Over the years, the importation of whole classes of ships was progressively substituted by local assembly, and then complete local production, starting with the smallest ships, such as torpedo boats and cruisers in the 1880s, to finish with whole battleships in the early 1900s. The last major purchase was in 1913 when the battlecruiser Kongō was purchased from the Vickers shipyard. By 1918, there was no aspect of shipbuilding technology where Japanese capabilities fell significantly below world standards. By 1920, the Imperial Japanese Navy was the world's third largest navy, and was a leader in many aspects of naval development:

• The Japanese Navy was the first navy in the world to use wireless telegraphy in combat (following its 1897 invention by Marconi), at the 1905 Battle of Tsushima.
• In 1906, it launched the battleship Satsuma, at the time the largest warship in the world by displacement, and the first ship in the world to be designed, ordered and laid down as an "all-big-gun" battleship, about one year before the British HMS Dreadnought.
• Between 1905 and 1910, Japan started to build battleships domestically. The 1906 battleship Satsuma was built in Japan with about 80% parts from Britain, but the next battleship class, the 1910 Kawachi was built with only 20% imported parts.

World War I

Japan entered World War I on the side of the Allies, against Germany and Austria, as a natural prolongation of the 1902 Anglo-Japanese Alliance. After the Battle of Tsingtao, an Anglo-Japanese siege, the Japanese Navy seized the German naval base of Tsingtao on the Shantung peninsula in China, in November 1914. Concurrently a battle group was sent to the central Pacific in August and September to pursue the German East Asiatic squadron, which then moved into the Southern Atlantic, where it encountered British naval forces and was destroyed at the Battle of the Falkland Islands. Japan seized the former possessions of Germany in Micronesia on this occasion (the Mariana Islands (excluding Guam), Caroline Islands and Marshall Islands), which remained Japanese colonies until the end of World War II, under the League of Nations' South Pacific Mandate.

Hard pressed in Europe, where it had only a narrow margin of superiority against Germany, Britain had requested, but was denied, the loan of Japan's four newest Kongō-class battleships ( Kongō, Hiei, Haruna, Kirishima), the first ships in the world to be equipped with 14-inch (356 mm) guns, and the most advanced capital ships in the world at the time of their launch.

Following further request to contribute to the conflict, and the advent of unrestricted German submarine warfare from 1917, the Imperial Japanese Navy sent a special force of destroyers to the Mediterranean in March 1917. The fleet, consisting of one armoured cruiser, Nisshin, and eight of the Navy's newest destroyers under Admiral Satō Kōzō, was based in Malta and efficiently protected allied shipping between Marseilles, Taranto and ports in Egypt until the end of the War. One destroyer, Sakaki, was torpedoed by an Austrian submarine with the loss of 59 officers and men.

After the conflict, the Japanese Navy received seven German submarines as spoils of war, which were brought to Japan and analysed, contributing greatly to the development of the Japanese submarine industry.

Interwar years

In the years before WW II the IJN began to structure itself specifically to fight the United States. A long stretch of militaristic expansion and the start of the Second Sino-Japanese war in 1937 had alienated the United States, and the country was seen as a rival of Japan.

The Imperial Japanese Navy was faced, before and during World War II, with considerable challenges, probably more so than any other navy in the world. Japan, like Britain, was almost entirely dependent on foreign resources to supply its economy, so that the Imperial Japanese Navy had to secure and protect sources for raw material (especially Southeast Asian oil and raw materials) that were far away, and controlled by foreign countries (Britain, the United States and the Netherlands). To achieve this goal, she had to build large warships capable of a long range.

To achieve Japan’s expansionist policies, the Imperial Japanese Navy also had to fight off the largest navies in the world (The 1922 Washington Naval Treaty allotted a 5/5/3 ratio for the navies of Britain, the United States and Japan). She was therefore numerically inferior and her industrial base for expansion was limited (in particular compared to the United States). Her battle tactics therefore tended to rely on technical superiority (fewer, but faster, more powerful ships), and aggressive tactics (daring and speedy attacks overwhelming the enemy, a recipe for success in her previous conflicts).

During the interwar, Japan therefore took the lead in many areas of warship development:

• In 1921 it launched the Hōshō, the first purpose-designed aircraft carrier in the world to be completed, and subsequently developed a fleet of aircraft carriers second to none.
• In keeping with its belief in big-gun action, the Imperial Japanese Navy was the first navy to mount 14-in (356 mm) guns (with the Kongō), 16-in (406 mm) guns (with the Nagato), and the only Navy ever to mount 18.1-in (460 mm) guns (with the Yamato).
• In 1928, it launched the innovative Fubuki-class destroyer, introducing enclosed turrets capable of anti-aircraft fire and the 24-inch (610 mm) oxygen fuelled Type 93 torpedo. The new destroyer design was soon emulated by other navies.
• Japan developed the oxygen fuelled Type 93 "Long Lance" torpedo, generally recognized as the best torpedo in the world, down to the end of World War II (Westwood, Fighting Ships).

Japan sometimes continued to solicit foreign expertise in areas where it needed to catch up with the West: in 1921 it welcomed for a year and a half the Sempill Mission, a group of British aeronaval instructors who trained the Imperial Japanese Navy on several new aircraft, such as the Gloster Sparrowhawk, and various techniques such as torpedo bombing and flight control.

During the pre-war years, two schools of thought battled over whether the Navy should be organized around powerful battleships that could ultimately win over American ones in Japanese waters, or around an aggressive fleet of aircraft carriers. Neither really prevailed, and both lines of ships were developed, with the results that neither solution displayed overwhelming strength over the American adversary. A consistent weakness of Japanese warship development was the tendency to incorporate too much armament, and too much engine power, in comparison to ship size (a side-effect of the Washington treaty), leading to shortcomings in stability, protection and structural strength.

World War II

The Imperial Japanese Navy in World War Two was administered by the Ministry of the Navy of Japan and controlled by the Chief of the Imperial Japanese Navy General Staff at Imperial General Headquarters. In order to combat the numerically superior American navy, the IJN devoted large amounts of resources to creating a force superior in quality to any navy at the time. Consequently, at the beginning of World War II, Japan probably had the most sophisticated Navy in the world. Betting on the speedy success of aggressive tactics, Japan did not invest significantly on defensive organization: she should also have been able to protect her long shipping lines against enemy submarines, which she never managed to do, particularly under-investing in anti-submarine escort ships and escort aircraft carriers.

The Japanese Navy enjoyed spectacular success during the first part of the hostilities, but American forces ultimately managed to gain the upper hand through technological upgrades to its air and naval forces and a vastly stronger industrial output. Japan's reluctance to use their submarine fleet for commerce raiding and failure to secure their communications also added to their defeat. During the last phase of the war the Imperial Japanese Navy resorted to a series of desperate measures, including Kamikaze (suicide) actions by a variety of Special Attack Units.

Battleships

Japan continued to attribute considerable prestige to battleships and endeavoured to build the largest and most powerful ships of the period. Yamato, the largest and most heavily-armed battleship in history, was launched in 1941.

The second half of World War II saw the last battleship duels. In the Battle of Guadalcanal on November 15, 1942, the United States battleships South Dakota and Washington fought and destroyed the Japanese battleship Kirishima. In the Battle of Leyte Gulf on 25 October 1944 six battleships, led by Admiral Jesse Oldendorf of the U.S. 7th Fleet fired upon and claimed credit for sinking Admiral Shoji Nishimura's battleships Yamashiro and Fusō during the Battle of Surigao Strait; in fact, both battleships were fatally crippled by destroyer attacks before being brought under fire by Oldendorf's old battleships.

Nevertheless, the Battle of Samar on 25 October 1944 during the Battle of Leyte Gulf showed that battleships could still be useful, albeit inefficient weapons. Only the indecision of Admiral Takeo Kurita and the fight by American destroyers and destroyer escorts saved the American aircraft carriers of " Taffy 3" from being pounded to the bottom by the gunfire of Yamato, Kongō and Nagato and their cruiser host. Miraculously for the Americans, only USS Gambier Bay along with two destroyers and one destroyer escort were lost due to surface action. The Yamato, for all the expense that went into building her, failed to score even a single hit.

Ultimately, the advent of air power spelled doom for the battleship. Battleships in the Pacific ended up primarily performing shore bombardment and anti-aircraft defense for the carriers. The Yamato and Musashi were sunk by aircraft attacks long before they could come within striking range of the American fleet. As a result of the changing technology, plans for even larger battleships, such as the Japanese Super Yamato class, were cancelled.

Aircraft carriers

Japan put particular emphasis on aircraft carriers. The Imperial Japanese Navy started the Pacific War with 10 aircraft carriers, the largest and most modern carrier fleet in the world at that time. Its two Shōkakus were superior to any carrier in the world until the wartime appearance of the American Essex-class aircraft carrier. However, a large number of the Japanese carriers were of small size in accordance to limitations placed upon the Navy by the London and Washington Naval Conferences. There were 7 American aircraft carriers at the beginning of the hostilities, only 3 of them operating in the Pacific, and 3 British aircraft carriers, of which a single one operated in the Indian Ocean.

However, following the Battle of Midway, in which four Japanese carriers were sunk, the Japanese Navy suddenly found itself short of full fleet carriers, resulting in an ambitious set of projects to convert commercial and military vessels into escort carriers such as the Hiyō and Shinano, which became the largest aircraft carrier of World War II. The Navy also attempted to build a number of full fleet carriers, though most of these projects were not completed by the end of the war.

Naval aviation

Japan began the war with a highly competent naval air force designed around some of the best airplanes in the world: the " Zero" was considered the best carrier aircraft of the beginning of the war, the Mitsubishi G3M bomber was remarkable for its range and speed, and the Kawanishi H8K was considered as the world's best flying boat. The Japanese pilot corps at the beginning of the war were of high caliber as compared to their contemporaries around the world due to intense training practices and frontline experience in the Sino-Japanese War. The Navy also had a competent tactical bombing force based around the Mitsubishi G3M and G4M bombers, which astonished the world by being the first planes to sink enemy battleships under way, in the sinking of Prince of Wales and Repulse.

As the war dragged on, the Allies found weaknesses in Japanese Naval Aviation. Though most of the Japanese aircraft were characterized by having great operating ranges, they had very little in the way of defensive armament and armor. As a result, the more numerous, heavily armed and armored American aircraft were able to develop techniques that nullified the advantages of the Japanese aircraft. Although there were delays in engine development, several new competitive designs were developed during the war, but industrial weaknesses, lack of raw materials and disorganization due to Allied bombing raids hampered their mass-production. Furthermore, the IJN didn't have an efficient process for speedily replacing lost aviators, as several years of training were usually considered necessary. Therefore, they weren't able to effectively replace their seasoned pilots as they were lost through attrition following their initial successes in the Pacific campaign. The IJN pilot's later inexperience was especially evident during the Battle of the Philippine Sea when their aircraft were shot-down in droves by the American naval pilots in what the Americans later called the, "Great Marianas Turkey Shoot". Following the Battle of Leyte Gulf, the Japanese Navy increasingly opted towards deploying aircraft in the kamikaze role.

Towards the end of the conflict, several competitive plane designs were developed, such as the 1943 Shiden, but such planes were produced too late and in insufficient numbers (415 units for the Shiden) to affect the outcome of the war. Radical new plane designs were also developed, such as the canard design Shinden, and especially jet-powered aircraft such as the Nakajima Kikka and the rocket-fighter Mitsubishi J8M. These jet designs were partially based on technology received from Nazi Germany, usually in the form of a few drawings only, and Japanese manufacturers had to play a key role in the final engineering. These developments also happened too late in the conflict to have any influence on the outcome. The Kikka only flew once before the end of the war.

Submarines

Japan had by far the most varied fleet of submarines of World War II, including manned torpedoes ( Kaiten), midget submarines ( Ko-hyoteki, Kairyu), medium-range submarines, purpose-built supply submarines (many for use by the Army), long-range fleet submarines (many of which carried an aircraft), submarines with the highest submerged speeds of the conflict ( Senkou I-200), and submarines that could carry multiple bombers (WWII's largest submarine, the Sentoku I-400). These submarines were also equipped with the most advanced torpedo of the conflict, the oxygen-propelled Long Lance. A plane from one such long-range fleet submarine, I-25, conducted what is still the only aerial bombing attack on the continental United States when Warrant Flying Officer Nobuo Fujita attempted to start massive forest fires in the Pacific Northwest outside the town of Brookings, Oregon on September 9th, 1942. Other submarines undertook trans-oceanic missions to German-occupied Europe, such as I-30, I-8, I-34, I-29 and I-52, in one case flying a Japanese seaplane over France in a propaganda coup. In May 1942, Type A midget submarines were used in the Attack on Sydney Harbour, and the Battle of Madagascar.

Overall, despite their technical prowesses, Japanese submarines were relatively unsuccessful. They were often used in offensive roles against warships, which were fast, maneuverable and well-defended compared to merchant ships. In 1942, Japanese submarines managed to sink two fleet carriers, one cruiser, and a few destroyers and other warships, and damage several others. They were not able to sustain these results afterwards, as Allied fleets were reinforced and became better organized. By the end of the war, submarines were instead often used to transport supplies to island garrisons. During the war, Japan managed to sink about 1 million tons of merchant shipping (184 ships), compared to 1.5 million tons for Britain (493 ships), 4.65 million tons for the US (1,079 ships) and 14.3 million tons for Germany (2,840 ships).

Early models were not very maneuverable under water, could not dive very deep, and lacked radar. Later in the war units that were fitted with radar were in some instances sunk due to the ability of US radar sets to detect their emissions. For example, Batfish (SS-310) sunk three such equipped submarines in the span of four days. After the end of the conflict, several of Japan's most original submarines were sent to Hawaii for inspection in "Operation Road's End" ( I-400, I-401, I-201 and I-203) before being scuttled by the U.S. Navy in 1946 when the Soviets demanded to have access to the submarines as well.

Special Attack Units

At the end of the Second World War, numerous Special Attack Units (Japanese: 特別攻撃隊, tokubetsu kōgeki tai, also abbreviated to 特攻隊, tokkōtai) were developed for suicide missions, in a desperate move to compensate for the annihilation of the main fleet. These units included Kamikaze ("Divine Wind") bombers, Shinyo ("Sea Quake") suicide boats, Kairyu ("Sea Dragon") suicide midget submarines, Kaiten ("Turn of Heaven") suicide torpedoes, and Fukuryu ("Crouching Dragon") suicide scuba divers who would swim under boats and use explosives mounted on bamboo poles to destroy both the boat and themselves. Kamikaze planes were particularly effective during the defense of Okinawa, in which 1,465 planes were expended to damage around 250 American warships.

A considerable number of Special Attack Units were built and stored in coastal hideouts for the desperate defense of the Home islands, with the potential to destroy or damage thousands of enemy warships.

Self-Defense Forces

Following Japan's surrender to the United States at the conclusion of World War II, and Japan's subsequent occupation, Japan's entire imperial military was dissolved in the new 1947 constitution which states, "The Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes." Japan's current navy falls under the umbrella of the Japan Self-Defense Forces (JSDF) as the Japan Maritime Self-Defense Force (JMSDF).

Imperial Japanese Navy
Major battles		List of ships		List of aircraft		List of weapons		Main admirals