The was a fleet of the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, Potsdam Declaration, when it was dissolved followin ...

(IJN) that during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, had primary responsibility for the command of

submarine A submarine (often shortened to sub) is a watercraft capable of independent operation underwater. (It differs from a submersible, which has more limited underwater capability.) The term "submarine" is also sometimes used historically or infor ...

operations.

History

The 6th Fleet was formed on 15 November 1940, and was assigned general control of all IJN submarine operations. Its initial mission was reconnaissance off the west coast of the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, east coast of

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, and the

sea lane A sea lane, sea road or shipping lane is a regularly used navigable route for large water vessels (ships) on wide waterways such as oceans and large lakes, and is preferably safe, direct and economic. During the Age of Sail, they were determined ...

s of the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

Background

Japan had prior to the

attack on Pearl Harbor The attack on Pearl HarborAlso known as the Battle of Pearl Harbor was a surprise military strike by the Empire of Japan on the United States Pacific Fleet at Naval Station Pearl Harbor, its naval base at Pearl Harbor on Oahu, Territory of ...

a diverse submarine fleet, some of which had unique distinctions: the only submarines in existence of over 5,000 tons submerged

displacement Displacement may refer to: Physical sciences Mathematics and physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

, submarines over 400 feet in length (until the advent of

nuclear power Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by ...

), the 41 submarines in its retinue (and of the world) that could carry specially designed aircraft, and submarines with the longest ranges and highest speeds of any nation. With the development of the Type 95 submarine-launched variant of the Long Lance oxygen-propelled torpedo, Japan not only had the world's most advanced torpedo, but one with the largest warhead. Despite these advantages, IJN submarines achieved remarkably little during World War II primarily having in hindsight suffered from the antiquated strategy of the

Imperial Japanese Navy General Staff The was the highest organ within the Imperial Japanese Navy (IJN). In charge of planning and operations, it was headed by an Admiral headquartered in Tokyo. History Created in 1893, the Navy General Staff took over operational (as opposed to a ...

, who viewed submarines as little more than scouts whose main role was to locate and shadow enemy naval task forces in preparation for a decisive surface conflict. Maybe the IJN General Staff was slow to change as the submarines were generally slow to dive, easy to track with radar and sonar, difficult to maneuver underwater, and less sturdy than their German U-boat counterparts.

Early stages of the Pacific War

At the start of the

Pacific War The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theatre, was the Theater (warfare), theatre of World War II fought between the Empire of Japan and the Allies of World War II, Allies in East Asia, East and Southeast As ...

midget submarine A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to six or nine, with little or no on-board living accommodation. They normally work with mother ships, from which they are launched an ...

s were used in preparatory reconnaissance of the

US Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

anchorage at

Pearl Harbor Pearl Harbor is an American lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. It was often visited by the naval fleet of the United States, before it was acquired from the Hawaiian Kingdom by the U.S. with the signing of the Reci ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

, and in the initial stages of the

. With the outbreak of general war, the mission of the 6th Fleet expanded to include shipping interdiction and mine laying. A few specialized missions, such as the

attack on Sydney Harbour From 31 May to 8 June 1942, during World War II, Imperial Japanese Navy submarines made a series of attacks on the Australian cities of Sydney and Newcastle, New South Wales, Newcastle. On the night of 31 May – 1 June, three Ko-hyoteki class ...

with the use of midget submarines were also undertaken. The 6th fleet cooperated briefly with the

Kriegsmarine The (, ) was the navy of Nazi Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official military branch, branche ...

(German navy) in the

in operations to interdict

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commerce from its base in

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, but these missions were few. The IJN General Staff placed more emphasis on ambush operations of Allied

capital ship The capital ships of a navy are its most important warships; they are generally the larger ships when compared to other warships in their respective fleet. A capital ship is generally a leading or a primary ship in a naval fleet. Strategic i ...

s. In 1942, Japanese submarines were credited with sinking two

aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...

s, one

cruiser A cruiser is a type of warship. Modern cruisers are generally the largest ships in a fleet after aircraft carriers and amphibious assault ships, and can usually perform several operational roles from search-and-destroy to ocean escort to sea ...

and several

destroyer In naval terminology, a destroyer is a fast, maneuverable, long-endurance warship intended to escort larger vessels in a fleet, convoy, or carrier battle group and defend them against a wide range of general threats. They were conceived i ...

s, as well as damaging one aircraft carrier and two

battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...

s. The success of 1942 was difficult to repeat in forthcoming years with the vast scale of the World War II Pacific conflict, which made it difficult for a submarine to be in "right place at the right time" to make a successful attack, and the increased anti-submarine attention and capabilities by the US Navy.

Latter stages of the Pacific War

After 1942, the IJN General Staff had little support to continue submarine use in commerce interdiction or ambush operations. Instead, the massive Japanese surface vessel losses in such actions as the

Solomon Islands campaign The Solomon Islands campaign was a major military campaign, campaign of the Pacific War during World War II. The campaign began with the Empire of Japan, Japanese seizure of several areas in the British Solomon Islands and Bougainville Island, B ...

called for numerous submarine sorties to defend the transport of critical supplies and reinforcements to isolated military island posts instead of offensive military actions. Development of anti-submarine warfare by the US Navy resulted in ever-increasing losses for the IJN: they started the war with 63 ocean-going submarines (not including midgets), and completed construction of 111 during the war. Of these 174 IJN vessels, 128 were lost during the conflict and most of the surviving equipment were training vessels, or having been completed so near the end of the war never saw combat. None of the 30 submarines that supported the attack on Pearl Harbor survived the war. Kwajalein in the

Marshall Islands The Marshall Islands, officially the Republic of the Marshall Islands, is an island country west of the International Date Line and north of the equator in the Micronesia region of the Northwestern Pacific Ocean. The territory consists of 29 c ...

was the main base for Japanese submarine operations in the Pacific until it fell to the US in February 1944; the 6th fleet headquarters was relocated to

Saipan Saipan () is the largest island and capital of the Northern Mariana Islands, an unincorporated Territories of the United States, territory of the United States in the western Pacific Ocean. According to 2020 estimates by the United States Cens ...

in the

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. The latter's fall to the US in July 1944 resulted in the deaths of the 6th fleet commander-in-chief Admiral Takeo Takagi and most of his staff. The increased vigilance of the US Fleet during the Battle of the Philippines, and until of the war, relegated IJN submarine use largely as carriers for '' kaiten'' suicide missions. The final sortie of the 6th fleet was after the termination of the war, when the super submarine Japanese submarine ''I-401'' returned to

Yokosuka is a city in Kanagawa Prefecture, Japan. , the city has a population of 373,797, and a population density of . The total area is . Yokosuka is the 11th-most populous city in the Greater Tokyo Area, and the 12th in the Kantō region. The city i ...

from

Ulithi Ulithi (, , or ; pronounced roughly as YOU-li-thee) is an atoll in the Caroline Islands of the western Pacific Ocean, about east of Yap, within Yap State. Name The name of the island goes back to Chuukic languages, Proto-Chuukic ''*úlú-diw ...

Organization

15 November 1940

*Submarine Squadron 1 : Training cruiser ''Katori'' (Flagship), Submarine tender ''Taigei'', Submarine ''I-20'' **Submarine Division 1 : Submarine ''I-15'', ''I-16'', ''I-17'' *Submarine Squadron 2 : Light cruiser ''Isuzu'' **Submarine Division 11 : Submarine ''I-74'', ''I-75'' **Submarine Division 12 : Submarine ''I-68'', ''I-69'', ''I-70'' **Submarine Division 20 : Submarine ''I-71'', ''I-72'', ''I-73'' *Submarine Squadron 3 : Submarine tender ''Chōgei'', Submarine ''I-7'' **Submarine Division 7 : Submarine ''I-1'', ''I-2'', ''I-3'' **Submarine Division 8 : Submarine ''I-4'', ''I-5'', ''I-6''

1 December 1941

*Training cruiser ''Katori'' (Flagship), Fleet oiler ''Ondo'' *Submarine Squadron 1 : Auxiliary submarine tender ''Yasukuni Maru'', Submarine ''I-9'' **Submarine Division 1 : Submarine ''I-15'', ''I-16'', ''I-17'' **Submarine Division 2 : Submarine ''I-18'', ''I-19'', ''I-20'' **Submarine Division 3 : Submarine ''I-21'', ''I-22'', ''I-23'' **Submarine Division 4 : Submarine ''I-24'', ''I-25'', ''I-26'' *Submarine Squadron 2 : Auxiliary submarine tender ''Santos Maru'', Submarine ''I-7'', ''I-10'' **Submarine Division 7 : Submarine ''I-1'', ''I-2'', ''I-3'' **Submarine Division 8 : Submarine ''I-4'', ''I-5'', ''I-6'' *Submarine Squadron 3 : Submarine tender ''Taigei'', Submarine ''I-8'' **Submarine Division 11 : Submarine ''I-74'', ''I-75'' **Submarine Division 12 : Submarine ''I-68'', ''I-69'', ''I-70'' **Submarine Division 20 : Submarine ''I-71'', ''I-72'', ''I-73''

15 June 1944

6th Fleet does not have a flagship, because the headquarters moved ashore. *Submarine ''I-10'' *Submarine Squadron 7 **Submarine Division 51 : Submarines ''Ro-109'', ''Ro-112'', ''Ro-113'', ''Ro-114'', ''Ro-115'', ''Ro-117'' * Submarine Squadron 8: Submarine ''I-8'', ''I-26'', ''I-27'', ''I-29'', ''I-37'', ''I-52'', ''I-165'', ''I-166'', ''Ro-501'' *Submarine Squadron 11 : Submarine tender ''Chōgei'', Submarine ''I-33'', ''I-46'', ''I-54'', ''I-55'', ''I-361'', ''I-362'', ''Ro-46'', ''Ro-48'' *Submarine Division 7 : Submarine ''I-5'', ''I-6'' *Submarine Division 12 : Submarine ''I-169'', ''I-174'', ''I-175'', ''I-176'' *Submarine Division 15 : Submarine ''I-16'', ''I-32'', ''I-36'', ''I-38'', ''I-41'', ''I-44'', ''I-45'', ''I-53'' *Submarine Flotilla 22 : Submarine ''I-177'', ''I-180'', ''I-183'', ''I-184'', ''I-185'' *Submarine Flotilla 34 : Submarine ''Ro-36'', ''Ro-41'', ''Ro-42'', ''Ro-43'', ''Ro-44'', ''Ro-45'', ''Ro-47''

1 June 1945

*Patrol Squadron 22 : Auxiliary boom defence vessel ''Kiku-maru'' **4 Patrol Divisions *Hunter-Killer Squadron 31 : Destroyer ''Hanazuki'' **Destroyer Division 17 : Destroyer ''Yukikaze'' **Destroyer Division 41 : Destroyer ''Suzutsuki'', ''Fuyutsuki'' **Destroyer Division 43 : Destroyer ''Take'', ''Kiri'', ''Maki'', ''Sii'' **Destroyer Division 52 : Destroyer ''Sugi'', ''Kashi'', ''Kaba'', Escort ship ''CD-31'', ''CD-43'' *Submarine Squadron 11 : Submarine tender ''Chōgei'', Submarine ''I-201'', ''I-202'', ''I-203'' *Submarine Division 1 : Submarine ''I-13'', ''I-400'', ''I-401'' *Submarine Division 15 : Submarine ''I-36'', ''I-47'', ''I-53'', ''I-58'' *Submarine Division 16 : Submarine ''I-369'', ''I-372'', ''Ha-101'', ''Ha-102'', ''Ha-104'' *Submarine Division 34 : Submarine ''Ha-109''

Commanders of the IJN 6th Fleet

Commander in chiefWendel, Axis History Database Chief of staff

References

Notes

Books

* * * *

External links

* * * {{Imperial Japanese Navy warship units 6 Military units and formations established in 1940 J Military units and formations disestablished in 1945 1945 disestablishments in Japan