Imperial Japanese Navy submarines originated with the purchase of five Holland type submarines from the United States in 1904. Japanese submarine forces progressively built up strength and expertise, becoming by the beginning of World War II one of the world's most varied and powerful submarine fleets.

Origins

The Imperial Japanese Navy (IJN) acquired its first submarines during the Russo-Japanese War on 12 December 1904 where they arrived in sections at the Yokohama dockyards. The vessels were purchased from the relatively new American company, Electric Boat, and were fully assembled and ready for combat operations by August 1905.Jentschura p. 160 However, hostilities with Russia were nearing its end by that date, and no submarines saw action during the war.

The submarines that Electric Boat sold to Japan were based on the Holland designs, known as Holland Type VIIs similar to the American s. The five imported Hollands were originally built at Fore River Ship and Engine Company in Quincy, Massachusetts under Busch's direction for the Electric Boat Company back in August–October 1904. They were shipped by freighter from Seattle, Washington in Knock-down kit form to Japan, and then reassembled by Arthur Leopold Busch at the Yokosuka Naval Arsenal, which was then Japan's largest naval shipyard, to become Hulls No. 1 through 5 and were designated Type 1 submarines by the Japanese Navy.

Frank Cable, an electrician who was working for Isaac Rice's Electro-Dynamic and Storage Companies along with Rice's Electric Boat, arrived some six months after Busch, training the IJN in the operation of the newly introduced vessels.

In 1904 Kawasaki Dockyard Company purchased plans for a modified version directly from Holland, and built two boats (Hulls No. 6 and 7), with the help of two American engineers, Chase and Herbert, who had been assistants to Holland. The Kawasaki-type submarines displaced 63 and 95 tons when submerged, and measured in overall length, respectively. Both vessels measured at the beam. This contrasted with the original five imported Hollands-type submarines which had arrived that same year, at over 100 tons submerged, in overall length and beam. The Kawasaki Type #6 and #7 submarines had gained extra speed and reduced fuel consumption by . However both boats could launch only one torpedo, and each was manned by 14 sailors, whereas the imported Holland-type submarines could fire two torpedoes and could be operated by 13 sailors. This new type was designated the Type 6 submarine by the Imperial Japanese Navy, and was used primarily for test purposes.

The Kaigun Holland #6 was launched at Kobe on 28 September 1905 and was completed six months later at Kure as the first submarine built in Japan. It sank during a training dive in Hiroshima Bay on 15 April 1910. Although the water was only deep, there were no provisions at all for the crew to escape while submerged. The commanding officer, Lieutenant Tsutomu Sakuma, patiently wrote a description of his sailor's efforts to bring the boat back to the surface as their oxygen supply ran out. All of the sailors were later found dead at their duty stations when this submarine was raised the following day. The sailors were regarded as heroes for their calm performance of their duties until death,Baldwin pp. 92–110 and this submarine was preserved as a memorial in Kure until the end of World War II.

Although the capabilities of these first submarines were never tested in combat during the Russo-Japanese War, the first submarine squadron was soon formed at Kure Naval District in the Inland Sea. Following the war, the Japanese government followed submarine developments by the Royal Navy with interest, and purchased two British C-class submarines directly from Vickers, with an additional three built from kits by the Kure Naval Arsenal. These became respectively the Japanese and submarines. An additional two vessels, forming the were later built by the Kure Naval Arsenal.

In 1909, the first submarine tender, , was commissioned.

World War I Japan, along with the rest of the Allies, drew heavily upon Germany's Guerre de Course (commerce raiding) operations during the First World War, and their submarine successes reinforced Japan's willingness to develop this weapon, resulting in eighteen ocean-going submarines being included in its 1917 expansion program. Japan received nine German submarines as World War I reparations, which allowed her and the other Allies to accelerate their technological developments during the interwar period.

World War II

Imperial Japanese Navy (IJN) submarines formed by far the most varied fleet of submarines of World War II, including manned torpedoes (Kaiten), midget submarines (Kō-hyōteki, ), medium-range submarines, purpose-built supply submarines (many used by the Imperial Japanese Army, see Type 3), fleet submarines (many of which carried an aircraft), submarines with the highest submerged speeds of the conflict (Sentaka ), and submarines able to carry multiple bombers (World War II's largest submarine, the Sentoku ). They were also equipped with the advanced oxygen-fuelled Type 95 Torpedo (which are sometimes confused with the famed Type 93 Long LanceBoyne pp. 127, 254 torpedo). Overall, despite their advanced technical innovation, Japanese submarines were built in relatively small numbers, and had less effect on the war than those of the other major navies.

Paul Wenneker, the German naval attaché in Japan, suggested that Japanese submarines be used to attack American supply ships traveling between the U.S. West Coast and Hawaii, as Germany's U-boats were doing in the Atlantic. The Japanese rejected his advice, believing that submarines should only be used to attack U.S. Navy warships. The Imperial Japanese Navy's doctrine of fleet warfare (guerre d'escadre) resulted in its submarines seldom posing a threat to allied merchant convoys and shipping lanes, in contrast to the Kriegsmarine's U-boats who pursued commerce raiding against Allied and neutral merchant ships. During the war, IJN submarines sunk only about 1 million tons (GRT) of merchant shipping (184 ships) in the Pacific; by contrast U.S. Navy submarines sank 5.2 million tons (1,314 ships) in the same period,Blair, Silent Victory, p. 878 while U-boats of Nazi Germany's Kriegsmarine, the IJN's Axis partner, sank 14.3 million tons (2,840 ships) in the Atlantic and other oceans.

The IJN pursued the doctrine of guerre d'escadre (fleet vs fleet warfare), and consequently submarines were often used in offensive roles against warships. Warships were more difficult to attack and sink than merchant ships, however, because naval vessels were faster, more maneuverable, and better defended. Nonetheless, the IJN submarine arm did have a number of notable successes against US Navy warships during the first year of the Pacific War, at a time when American production of new warships had not caught up. During this time, US Navy submarines achieved few major Japanese warship kills, being led by timid and unproductive submarine skippers, as well as being equipped with unreliable torpedoes that either ran too deep or had faulty triggers.

However, as fuel oil diminished and air superiority was lost, Japanese submarines were no longer able to continue with such successes. Once the United States was able to increase its production of destroyers and destroyer escorts, as well as bringing over highly effective anti-submarine techniques learned during the Battle of the Atlantic, they took a heavy toll upon Japanese submarines. Early models of IJN submarines were relatively less maneuverable under water, could not dive very deeply (compared to Kriegsmarine U-boats), and lacked radar. Later in the war, Japanese submarines that were fitted with radar were in some instances sunk due to the ability of American radar sets to detect their emissions. For example, sank three such IJN submarines near Japan in just four days).

During the last two years of the War in the Pacific, many IJN submarines were also pressed into service delivering supplies to isolated island garrisons, ones that had been deliberately bypassed by the Americans and the Australians island-hopping campaign. These Japanese-held island bases could not be reached by surface transports because of blockades by Allied warplanes and naval vessels, however Japanese submarines in this role were generally inefficient as they could only transport a fraction of the goods that could be carried by surface ships.

After the end of the conflict, several of Japan's most innovative and advanced submarines were sent to Hawaii for inspection in "Operation Road's End" (, I-401, , and I-203) before being scuttled by the U.S. Navy in 1946 when the Soviet Union demanded access to the IJN submarines.

Successes against Allied warships Twice in the first year of the war, Japanese submarines torpedoed the aircraft carrier , and, while not sinking her, put her in the repair yard at a time when the US Navy could ill afford to do without her. Saratoga was torpedoed by submarine on January 11, 1942, putting her out of action and unavailable to participate in the desperate carrier battles and raids of the next five months, and then hit again three months after her return on September 1, 1942, by , which put her out of action for another eleven weeks in the middle of the intensely engaged land-air-sea battles of the Guadalcanal Campaign.

During the Battle of Midway, administered the final coup de grace that sank the crippled fleet carrier , as well as sinking the destroyer . A few months later, on September 15, 1942, with a single salvo of torpedoes, Japanese submarine sank the fleet carrier and damaged both the battleship and the destroyer . On November 13, 1942, the submarine torpedoed and sank the anti-aircraft cruiser , and a year later on November 23, 1943, the submarine torpedoed and sank the escort carrier , both with heavy loss of life. The had the distinction of both severely damaging the heavy cruiser , knocking her out of the war for a year, on October 20, 1942, and of also sinking (the only American submarine to be sunk by a Japanese submarine in the entire war) on November 16, 1943.

The Japanese submarine arm had few notable successes against Allied warships during the final two years of the war. One victory was the knocking the anti-aircraft cruiser out for the rest of the war with a torpedo hit on November 3, 1944 (this was the first time in almost two years that a Japanese submarine had successfully attacked an Allied ship operating with a fast carrier task force). On July 30, 1945, just two weeks before the Japanese surrender, torpedoed and sank the heavy cruiser , with heavy loss of life, at a time when few in the United States Navy expected continued Japanese submarine attacks.

Submarine aircraft carriers

The Japanese applied the concept of the "submarine aircraft carrier" extensively, starting with the J3 type of 1937–38. Altogether 41 submarines were built with the capability to carry seaplanes. Most IJN submarine aircraft carriers could carry only one aircraft, but I-14 had hangar space for two, and the giant , three.

Attacks upon continental USA A plane launched from one of the innovative aircraft-carrying submarines, , conducted what remains the only ever aerial bombing attack on the continental United States, when Warrant Flying Officer Nobuo Fujita piloting a Yokosuka E14Y scouting plane dropped four 168-pound bombs in an attempt to start forest fires outside the town of Brookings, Oregon, on September 9, 1942. Earlier in the year, in February 1942, the submarine fired a number of shells from her deck gun at the Elwood Oil Fields near Santa Barbara, California. None of the shells caused any serious damage.

Yanagi missions