Imperial Japanese Navy

The Imperial Japanese Navy (IJN) (大日本帝國海軍 Dai-Nippon Teikoku Kaigun or 日本海軍 Nippon Kaigun) was the navy of Japan before 1945. It 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.

World War II

(See also the article the Imperial Japanese Navy of World War Two)

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the years before WW II the IJN began to structure itself specifically to fight the US. A long stretch of militaristic expansion and the start of the Second Sino-Japanese war in 1937 had alienated the US and America was seen more often as the enemy of Japan.

Related Topics:
Militaristic - Second Sino-Japanese war

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Strategic overview

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 Great 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 (Great Britain, the United States and Holland). 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 Great 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). 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.

Related Topics:
Washington Naval Treaty - World War II - Anti-submarine - Escort aircraft carriers

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

Related Topics:
Battleships - Aircraft carriers

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Although the Japanese Navy enjoyed spectacular success during the first part of the hostilities, 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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Battleships

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

Related Topics:
Battleships - ''Yamato''

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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. 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 6 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. Japanese aircraft carriers, such as the Shokaku and Zuikaku, exceeded any in the world in performance and capability, until the wartime development of the American Essex-class aircraft carrier.

Related Topics:
Aircraft carrier - Pacific War - ''Shokaku'' - ''Zuikaku'' - ''Essex''-class aircraft carrier

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 IJN Hiyo and IJN 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.

Related Topics:
Battle of Midway - IJN Hiyo - IJN Shinano

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Naval Aviation

Main article:Imperial Japanese Navy Air Service

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Japan began the war with a competent naval air force designed around the best naval fighter plane of the era, the Mitsubishi Zero. The Japanese pilot corps at the begining 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 an enemy battleship under way, the HMS Prince of Wales and HMS Repulse.

Related Topics:
Mitsubishi Zero - Sino-Japanese War - G3M - G4M - HMS ''Prince of Wales'' - HMS ''Repulse''

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

As the war dragged on, the Allies were quick to find weaknesses in Japanese Naval Aviation. Though most of the Japanese aircraft were characterized by having great operating ranges, they had very little in the war of defensive armament and armor. As a result, the more numerous, heavily armed and armored American aircraft were able to develop techniques that quickly nullified the advantages of the Japanese aircraft. Furthermore, due to delays in engine development, the Japanese Navy had great difficulty in developing new and more competitive designs during the war, resulting in the mass scale production of aircraft with known weaknesses. Following the Battle of Leyte Gulf, the Japanese Navy increasingly opted towards deploying aircraft in the kamikaze role.

Related Topics:
Battle of Leyte Gulf - Kamikaze

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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 (Sentaka I-200), and submarines that could carry multiple bombers (WWII's largest submarine, the Sentoku I-400). These submarines were also equiped 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 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.

Related Topics:
Submarines - World War II - Kaiten - Ko-hyoteki - Kairyu - Sentaka I-200 - Sentoku I-400 - Long Lance - Brookings, Oregon

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Overall, despite their technical prowesses, Japanese submarines were relatively unsuccesfull. 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 Great 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 Hawai for inspection in "Operation Road's End" (I-400, I-401, I-201 and I-203) before being scuttled by the US Navy in 1946 when the Soviets demanded to have access to the submarines as well.

Related Topics:
Radar - ''Batfish'' (SS-310) - I-400 - I-201

~ ~ ~ ~ ~ ~ ~ ~ ~ ~