South Seas Force

The 4th Fleet (第四艦隊^?, 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.

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.

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.

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