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The 4th Fleet (第四艦隊 (日本海軍) Dai-yon Kantai?) was a fleet designation of the Imperial Japanese Navy. The Fourth Fleet designation was used during three separate periods. The initial designation was for a group of ships that were assigned to work together during the Russo-Japanese conflict and the period of its immediate aftermath. The second time the designation was used was during the Sino-Japanese conflict, and the third time was as a South Pacific area of command during the middle of the Pacific War.


Russo-Japanese War

First established on June 14, 1905, the 4th Fleet was created after the Battle of Tsushima in the Russo-Japanese War specifically to support and cover the landings of Japanese forces in Sakhalin. Afterwards, it was sent to the United States with the Japanese delegation negotiating the Treaty of Portsmouth ending the war, and was disbanded on December 20, 1905.

The Fourth Fleet Incident

While participating in war game maneuvers in 1935 the Fourth Fleet became caught in extremely foul weather. The weather continued to deteriorate and by 26 September had reached typhoon status. Two of the newer, large Special Type destroyers, the Hatsuyuki and the Yugiri, had their bows torn away by the heavy seas. A number of recently built heavy cruisers also suffered significant structural damage. The Myoko, the Mogami and the submarine tender Taigei developed serious cracks in their hulls, and the light aircraft-carriers Hōshō and Ryujo suffered damage to their flight decks and superstructure, with the Ryujo also having her hangar section flooded. The minelayer Itsukushima suffered damage that required several months for extensive repairs, necessitating a near complete rebuild. Nearly all the fleet's destroyers suffered damage to their superstructures, and fifty-four crewmen were lost, swept overboard or killed outright.[1] The Japanese Admiralty held a hearing on the damage suffered by Fourth Fleet in the storm, resulting in recommendations for changes on Japanese warship design and construction. A number of new designs that used heavier guns and taller superstructures were found to be top heavy, and efforts were made to stabilize these ships by reducing weight above the waterline. In addition cracks in the hulls of the new cruisers indicated the recently adopted practice of electric welding hull seams was suspect, and the practice was canceled on all new Japanese warship construction.[2] The event was kept a secret from the public. A similar event occurred to the US Third Fleet some nine years later in December 1944 when it faced Typhoon Cobra.

Second Sino-Japanese War

On October 20, 1937, the 4th Fleet was resurrected as part of the emergency reinforcement program for the China Area Fleet after the North China Incident of 1937. The new 4th fleet was based out of Tsingtao and assigned to patrol the Bohai Sea and the East China Sea regions. However, unlike the IJN 5th Fleet, the 4th Fleet was never in actual combat. On November 15, 1939, the 4th Fleet was absorbed into the 3rd China Expeditionary Fleet under the overall aegis of the China Area Fleet. Although most of its ships were released for service with the Combined Fleet in the Pacific War a year later, most of the staff for the 4th Fleet remained in China, and were assigned to the Tsingtao Base Force for the duration of the war.

Pacific War

On the same date at that the 4th Fleet was absorbed into the China Area Fleet, a new 4th Fleet was created to provide administrative control over Japanese naval forces in the Japanese-held island territories of the South Pacific (Caroline Islands, Marshall Islands, Mariana Islands, Palau). This third IJN 4th Fleet came under the aegis of the Combined Fleet on November 15, 1940.[3] The operational name of this fleet was the South Seas Force. With the start of hostilities against the United States, the 4th Fleet was based out of Truk,[4] with a secondary base at Kwajalein. After initial Japanese successes, additional bases were established in the southern Philippines, Guam, Wake Island, Gilbert Islands, eastern New Guinea, Bismarck Archipelago and the Solomon Islands.

After the Battle of the Coral Sea, the area covered by the 4th Fleet was reduced to an “inner core” of Japanese possessions, while the new IJN 8th Fleet was assigned to confront the advancing American forces in the Solomon Islands and New Guinea. However, in November 1943, the Americans attacked the Gilbert Islands and captured the major naval base of Tarawa, which brought the 4th Fleet and its various garrison forces back into the front lines of combat.

The Americans continued to advance through the Gilbert and Marshall Islands in early 1944, capturing the IJN 4th Fleet HQ in Truk in February, and pushing the surviving units back to Palau, which also proved vulnerable to air attack.

In March 1944, the IJN 4th Fleet came under operational control of the Central Pacific Area Fleet based in Saipan. It effectively ceased to exist with the fall of Saipan to American forces.[5]


Russo-Japanese War

Second Sino-Japanese War

  • Flagship: Ashigara
  • Cruiser Division 9: Myōkō, Nagara
  • Cruiser Division 14: Tenryū, Tatsuta
  • No.4 Torpedo Squadron: Kiso,
    • Destroyer Division 6
    • Destroyer Division 10
    • Destroyer Division 11
  • No.5 Torpedo Squadron: Natori
    • Destroyer Division 5
    • Destroyer Division 22

Order of Battle at time of Pearl Harbor

Commanders of the 4th Fleet

Commander in chief [6]
Rank Name Date
Admiral Baron Dewa Shigeto 14 Jun 1905 – 20 Dec 1905
Disbanded 20 Dec 1905 – 20 Oct 1937
Admiral Soemu Toyoda 20 Oct 1937 – 15 Nov 1938
Vice-Admiral Masaharu Hibino 15 Nov 1938 – 15 Nov 1939
Vice-Admiral Eikichi Katagiri 15 Nov 1939 – 15 Nov 1940
Admiral Shiro Takasu [5 Nov 1940 – 11 Aug 1941
Admiral Shigeyoshi Inoue 11 Aug 1941 – 26 Oct 1942
Vice-Admiral Baron Tomoshige Samejima 26 Oct 1942 – 1 Apr 1943
Vice-Admiral Masami Kobayashi 1 Apr 1943 – 19 Feb 1944
Vice-Admiral Chuichi Hara 19 Feb 1944 – 2 Sep 1945
Chief of Staff
Rank Name Date
Admiral Tanin Yamaya 14 Jun 1905 – 20 Dec 1905
Disbanded 20 Dec 1905 – 20 Oct 1937
Vice-Admiral Masami Kobayashi 20 Oct 1937 – 1 Sep 1938
Vice-Admiral Arata Oka 1 Sep 1938 – 15 Nov 1939
Vice-Admiral Fukuji Kishi 15 Nov 1939 – 10 Oct 1941
Vice-Admiral Shikazo Yano 10 Oct 1941 – 1 Nov 1942
Rear-Admiral Shunsaku Nabeshima 1 Nov 1942 – 6 Jan 1944
Rear-Admiral Michio Sumikawa 6 Jan 1944 – 30 Mar 1944
Vice-Admiral Kaoru Arima 30 Mar 1944 – 12 Aug 1944
Rear-Admiral Michio Sumikawa 12 Aug 1944 – 2 Sep 1945


  1. Evans, David; Peattie, Mark (1997). Kaigun: Strategy, Tactics and Technology in the Imperial Japanese Navy 1887-1941. Naval Institute Press. p. 243. ISBN 0-87021-192-7. 
  2. Hideo Kobayashi. "Failure Knowledge Database: The Fourth Fleet Incident". Tokyo Institute of Technology. 
  3. Weinberg, Gerhard (1994). A World at Arms: A Global History of World War II. Cambridge University Press. p. 167. ISBN 0-521-44317-2. 
  4. Jeffery, Bill (2003). War in Paradise: World War II Sites in Truk Lagoon. Historical Preservation Office. ISBN 982-9067-01-7. 
  5. D'Albas 1965, p. ?.
  6. Wendel, Axis History Database retrieved 25 August 2007.
  • D'Albas, Andrieu (1965). Death of a Navy: Japanese Naval Action in World War II. Devin-Adair Pub. ISBN 0-8159-5302-X. 
  • Dull, Paul S. (1978). A Battle History of the Imperial Japanese Navy, 1941-1945. Annapolis, MD: US Naval Institute Press. ISBN 0-87021-097-1. 
  • Lacroix, Eric; Linton Wells (1997). Japanese Cruisers of the Pacific War. Annapolis, MD: US Naval Institute Press. ISBN 0-87021-311-3. 

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