IJN 6th Fleet
Encyclopedia
The was a fleet of the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the 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...

 during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, primarily responsible for command of submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 operations.

History

The IJN 6th Fleet was formed on 15 November 1940, and was assigned general control of all Japanese submarine operations. Its initial mission was reconnaissance off the west coast of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, east coast of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, and the sea lane
Sea lane
A sea lane or shipping lane is a regularly used route for ocean-going and Great Lakes vessels. In the time of sailing ships they were not only determined by the distribution of land masses but also the prevailing winds, whose discovery was crucial for the success of long voyages...

s of the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

.

Background

Prior to World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, Japan had a very diverse submarine fleet, including the only submarines of over 5,000 tons submerged displacement
Displacement (ship)
A ship's displacement is its weight at any given time, generally expressed in metric tons or long tons. The term is often used to mean the ship's weight when it is loaded to its maximum capacity. A number of synonymous terms exist for this maximum weight, such as loaded displacement, full load...

, or submarines over 400 feet in length until the advent of nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

. Japan was also unique in that it built 41 submarines that could carry aircraft: something no other nation had yet produced. Japan also had submarines with the longest ranges and highest speeds of any nation. With the development of the Type 95
Type 95 torpedo
The Type 95 torpedo was a torpedo of the Imperial Japanese Navy.It was based on the formidable Type 93 torpedo but had a smaller warhead, shorter range and a smaller diameter...

 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.Polar, Submarines of the Imperial Japanese Navy

Despite some advantages, Japanese 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. They achieved remarkably little during World War II, primarily due to the antiquated strategy of the Imperial Japanese Navy General Staff
Imperial Japanese Navy General Staff
The was the highest organ within the Imperial Japanese Navy. In charge of planning and operations, it was headed by an Admiral headquartered in Tokyo.-History:...

, which 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.

Early stages of the Pacific War

At the start of the Pacific War
Pacific War
The Pacific War, also sometimes called the Asia-Pacific War refers broadly to the parts of World War II that took place in the Pacific Ocean, its islands, and in East Asia, then called the Far East...

, Midget submarine
Midget submarine
A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to 6 or 8, with little or no on-board living accommodation...

s were used in preparatory reconnaissance of the US Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 anchorage at Pearl Harbor
Pearl Harbor
Pearl Harbor, known to Hawaiians as Puuloa, is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the U.S. Pacific Fleet...

, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, and in the initial stages of the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...

.
With the outbreak of general war, the mission of the IJN 6th Fleet expanded to include shipping interdiction and mine laying
Naval mine
A naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...

. A few specialized missions, such as the Attack on Sydney Harbour
Attack on Sydney Harbour
In late May and early June 1942, during World War II, submarines belonging to the Imperial Japanese Navy made a series of attacks on the cities of Sydney and Newcastle in New South Wales, Australia...

 with the use of midget submarines were also undertaken. The IJN 6th fleet cooperated briefly with the German Navy
German Navy
The German Navy is the navy of Germany and is part of the unified Bundeswehr .The German Navy traces its roots back to the Imperial Fleet of the revolutionary era of 1848 – 52 and more directly to the Prussian Navy, which later evolved into the Northern German Federal Navy...

 in the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 in operations to interdict British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 commerce from its base in Penang
Penang
Penang is a state in Malaysia and the name of its constituent island, located on the northwest coast of Peninsular Malaysia by the Strait of Malacca. It is bordered by Kedah in the north and east, and Perak in the south. Penang is the second smallest Malaysian state in area after Perlis, and the...

, but these missions were a minority. The Navy General Staff placed more emphasis on ambush operations of Allied capital ship
Capital ship
The capital ships of a navy are its most important warships; they generally possess the heaviest firepower and armor and are traditionally much larger than other naval vessels...

s. In 1942, Japanese submarines were credited with sinking two aircraft carrier
Aircraft carrier
An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations...

s, one cruiser
Cruiser
A cruiser is a type of warship. The term has been in use for several hundreds of years, and has had different meanings throughout this period...

 and several destroyer
Destroyer
In naval terminology, a destroyer is a fast and maneuverable yet long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against smaller, powerful, short-range attackers. Destroyers, originally called torpedo-boat destroyers in 1892, evolved from...

s, as well as damaging one aircraft carrier and two battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...

s.

However, the success of 1942 could not be repeated in 1943, due to increased anti-submarine
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....

 capabilities by the US Navy and to the vast scale of the Pacific conflict, which made it difficult for a submarine to be in “right place at the right time” to make a successful attack.

Latter stages of the Pacific War

After 1942, the Navy General Staff also gave very little support to continued commerce interdiction or ambush operations. Instead, submarines came to be increasingly used (especially after massive Japanese surface vessel losses in the Solomon Islands campaign
Solomon Islands campaign
The Solomon Islands campaign was a major campaign of the Pacific War of World War II. The campaign began with Japanese landings and occupation of several areas in the British Solomon Islands and Bougainville, in the Territory of New Guinea, during the first six months of 1942...

 for transport of critical supplies and reinforcements to the starving garrisons on isolated islands. The Japanese Navy expended hundreds of sorties on such missions, which might have otherwise been used offensively against the Allied war effort.

In the meantime, continuous developments in anti-submarine warfare by the US Navy resulted in ever-increasing losses for Japan's submarine fleet. Japan started the war with 63 ocean-going submarines (not including midgets), and completed 111 during the war, for a total of 174. Of this total, 128 vessels were lost during the conflict. Most of the survivors were either training vessels, or were else recently completed by the end of the war and never saw combat. Of the 30 submarines that supported the Pearl Harbor attack, none survived the war.

Kwajalein
Kwajalein
Kwajalein Atoll , is part of the Republic of the Marshall Islands . The southernmost and largest island in the atoll is named Kwajalein Island. English-speaking residents of the U.S...

 in the Marshall Islands
Marshall Islands
The Republic of the Marshall Islands , , is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator. As of July 2011 the population was 67,182...

 was the main base for Japanese submarine operations in the Pacific until it fell to the Americans in February 1944. IJN 6th fleet headquarters was relocated to Saipan
Saipan
Saipan is the largest island of the United States Commonwealth of the Northern Mariana Islands , a chain of 15 tropical islands belonging to the Marianas archipelago in the western Pacific Ocean with a total area of . The 2000 census population was 62,392...

 in the Mariana Islands
Mariana Islands
The Mariana Islands are an arc-shaped archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels north and along the 145th meridian east...

, which the fell to the Americans in July 1944 with the death of IJN 6th fleet commander in chief Admiral Takeo Takagi
Takeo Takagi
was an admiral in the Imperial Japanese Navy during World War II.-Biography:Takagi was a native of Iwaki city, Fukushima prefecture. He was a graduate of the 39th class of the Imperial Japanese Naval Academy, ranking 17th of 148 cadets in 1911...

 and most of his staff. The remnants of the IJN 6th fleet were based at Ulithi
Ulithi
Ulithi is an atoll in the Caroline Islands of the western Pacific Ocean, about 191 km east of Yap. It consists of 40 islets totalling , surrounding a lagoon about long and up to wide—at one of the largest in the world. It is administered by the state of Yap in the Federated States of...

 Atoll in the Caroline Islands
Caroline Islands
The Caroline Islands are a widely scattered archipelago of tiny islands in the western Pacific Ocean, to the north of New Guinea. Politically they are divided between the Federated States of Micronesia in the eastern part of the group, and Palau at the extreme western end...

 until the end of the war.

Japan's submarine forces were unable to provide much support during the Battle of the Philippines due to increased vigilance by the American fleet. In the final stages of the war, surviving submarines were largely used as carriers for kaiten
Kaiten
The Kaiten were manned torpedos and suicide craft, they were used by the Imperial Japanese Navy in the final stages of World War II.-History:...

suicide missions.

The final sortie of the IJN 6th fleet was after the termination of the war, when the super submarine Japanese submarine I-401
Japanese submarine I-401
The Sen Toku-class I-401 was once the largest submarine in the world. It was commanded by Lieutenant Commander Nobukiyo Nambu of the Imperial Japanese Navy during World War II...

 returned to Yokosuka
Yokosuka, Kanagawa
is a city located in Kanagawa, Japan. As of 2010, the city had an estimated population of 419,067 and a population density of 4,160 people per km². It covered an area of 100.62 km²...

 from Ulithi.

15 November 1940

  • Submarine Squadron 1 : Training cruiser Katori
    Japanese cruiser Katori
    was the lead ship of the Katori class of three light cruisers which served with the Imperial Japanese Navy during World War II. It is named after the noted Shinto shrine Katori Shrine in Chiba prefecture, Japan.-Background:...

     (Flagship), Submarine tender Taigei
    Japanese aircraft carrier Ryuho
    The was a Japanese Light aircraft carrier. Sole ship of her class, she was converted from a submarine tender. During World War II she operated mainly as aircraft transport but did participate in the First Battle of the Philippine Sea.-Conversion and commission:...

    , Submarine I-20
    • Submarine Flotilla 1 : Submarine I-15, I-16, I-17
  • Submarine Squadron 2 : Light cruiser Isuzu
    Japanese cruiser Isuzu
    was one of six s in the Imperial Japanese Navy. It was named after the Isuzu River, near Ise Shrine in the Chūbu region of Japan.-Background:Isuzu was the second of the six vessels completed in the Nagara-class of light cruisers, and like other vessels of her class, she was intended for use as...

    • Submarine Flotilla 11 : Submarine I-74, I-75
    • Submarine Flotilla 12 : Submarine I-68, I-69, I-70
    • Submarine Flotilla 20 : Submarine I-71, I-72, I-73
  • Submarine Squadron 3 : Submarine tender Chōgei, Submarine I-7
    • Submarine Flotilla 7 : Submarine I-1, I-2, I-3
    • Submarine Flotilla 8 : Submarine I-4, I-5, I-6

1 December 1941

  • Training cruiser Katori
    Japanese cruiser Katori
    was the lead ship of the Katori class of three light cruisers which served with the Imperial Japanese Navy during World War II. It is named after the noted Shinto shrine Katori Shrine in Chiba prefecture, Japan.-Background:...

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

15 June 1944

(The 6th fleet does not have a flagship, because the headquarters moved to the land.)
  • Submarine I-10
  • Submarine Squadron 7
    • Submarine Flotilla 51 : Submarine Ro-104, Ro-105, Ro-106, Ro-107, Ro-108, Ro-109, Ro-111, Ro-112, Ro-113, Ro-114, Ro-115, Ro-116, 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 Flotilla 7 : Submarine I-5, I-6
  • Submarine Flotilla 12 : Submarine I-169, I-174, I-175, I-176
  • Submarine Flotilla 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
    Japanese destroyer Hanazuki
    was an Akizuki-class destroyer of the Imperial Japanese Navy. Her name means " March". In June 1947, Hanazuki was turned over to United States as "DD-934", and was later sunk as target off Gotō Islands, Japan on 3 February 1948....

    • Destroyer Division 17 : Destroyer Yukikaze
      Japanese destroyer Yukikaze
      was a in service with the Imperial Japanese Navy during World War II. She was the only member of her class to survive the war. The attrition rate of Japanese destroyers was extremely high due to heavy, prolonged combat and the need to use them to transport supplies to scattered Japanese island...

    • Destroyer Division 41 : Destroyer Suzutsuki
      Japanese destroyer Suzutsuki
      was an Akizuki-class destroyer of the Imperial Japanese Navy. Her name means "Clear Moon ".On 6–7 April 1945, Suzutsuki escorted from the Inland Sea on her attack mission against the Allied forces fighting on Okinawa. Her bow was torn off by a torpedo from aircraft of Task Force 58, but survived...

      , Fuyuzuki
      Japanese destroyer Fuyuzuki
      was an Akizuki-class destroyer of the Imperial Japanese Navy. Her name means "Winter Moon".On 12 October 1944, while escorting the light cruiser from Yokosuka to the Inland Sea, she was hit on the bow by a torpedo fired from...

    • Destroyer Division 43 : Destroyer Take
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Kiri
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Maki
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Sii
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

    • Destroyer Division 52 : Destroyer Sugi
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Kashi
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Kaba
      Matsu class destroyer
      The were a class of destroyer built for the Imperial Japanese Navy , who referred to them as .-Design basis:The Matsu class were built late in World War II, and they were intended to be more cost-effective in response to the changing character of naval warfare at that time...

      , Escort ship CD-31, CD-43
  • Submarine Squadron 11 : Submarine tender Chōgei, Submarine I-201, I-202, I-203
  • Submarine Flotilla 1 : Submarine I-13, I-400, I-401
  • Submarine Flotilla 15 : Submarine I-36, I-47, I-53, I-58
  • Submarine Flotilla 16 : Submarine I-369, I-372, Ha-101, Ha-102, Ha-104
  • Submarine Flotilla 34 : Submarine Ha-109

Commanders of the IJN 6th Fleet

Commander in chief
Rank Name Date
1 Vice-Admiral Noboru Hirata 15 November 1940 21 July 1941
2 Vice-Admiral Mizumi Shimizu  21 July 1941 16 March 1942
3 Vice-Admiral Marquis Teruhisa Komatsu
Teruhisa Komatsu
-Notes:...

 
16 March 1942 21 June 1943
4 Vice-Admiral Takeo Takagi
Takeo Takagi
was an admiral in the Imperial Japanese Navy during World War II.-Biography:Takagi was a native of Iwaki city, Fukushima prefecture. He was a graduate of the 39th class of the Imperial Japanese Naval Academy, ranking 17th of 148 cadets in 1911...

 
21 June 1943 10 July 1944
5 Vice-Admiral Shigeyoshi Miwa
Shigeyoshi Miwa
-External links:*-Notes:...

 
10 July 1944 1 May 1945
6 Vice-Admiral Marquis Tadashige Daigo
Daigo Tadashige
Marquis was an admiral in the Imperial Japanese Navy during World War II.-Biography:Born in Chiyoda, Tokyo into a kuge family of court nobility related to the Fujiwara aristocracy, Daigo was a graduate of the Gakushuin Peers' school. He went on to graduate from the 40th class of the Imperial...

 
1 May 1945 15 September 1945


Chief of staff
Rank Name Date
1 Vice-Admiral Hisashi Ichioka 15 November 1940 6 January 1941
2 Vice-Admiral Hisashi Mito 6 January 1941 22 October 1942
3 Rear Admiral Hisagoro Shimamoto 22 October 1942 15 November 1943
4 Rear Admiral Kozo Nishina 15 November 1943 21 December 1944
5 Rear Admiral Hankyu Sasaki 21 December 1944 15 September 1945
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