The was a class of minesweepers of the Imperial Japanese Navy (IJN), serving during the 1930s and World War II. 6 vessels were built in 1922–29 under the Eight-eight fleet plan. They have two sub-classes, this article handles them collectively.

Background In 1920, the IJN developed an Eight-eight Fleet Plan which would provide them with eight modern battleships and eight battle cruisers. However, they did not forget the Hatsuse and Yashima, which had struck naval mines during the Russo-Japanese War; afraid of such events occurring again, the IJN also ordered the No.1-class of purpose-built minesweepers, to replace converted old destroyers in the minesweeping role.

As the IJN anticipated its minesweepers to operate in front of the main battle fleet, and therefore to encounter enemy warships, the No.1-class were more heavily armed than minesweepers of other nations, with each ship mounting two L/45 naval guns. In addition each ship could carry 50 naval mines, making them multi-purpose vessels visually resembling small destroyers.

Ships in classes

No.1 class Project number I1. 4 vessels were built in 1922–1925. W-4 was behind with the laid down by the Washington Naval Treaty. Ship Builder Laid down Launched Completed Fate W-1. The same shall apply hereafter. Harima Zōsen 10 May 1922 6 March 1923 30 June 1923 Sunk by air raid at Yamada Bay on 10 August 1945; removed from naval ship list on 15 September 1945. W-2 Mitsui, Tama Shipyard 13 April 1922 17 March 1923 30 June 1923 Sunk by friendly torpedo from Mogami or MikumaIn the vicinity of the wreck, many parts from a Type 93 torpedo were discovered. The Japanese destroyers which participated in the Battle of Sunda Strait were not equipped with Type 93 torpedoes. at Bantam Bay during the Battle of Sunda Strait on 1 March 1942; removed from naval ship list on 30 November 1945. W-3 Ōsaka Iron Works 29 March 1923 30 June 1923 Sunk by USS Parche at Ōfunato Bay on 9 April 1945; removed from naval ship list on 10 May 1945. W-4 Sasebo Naval Arsenal 1 December 1923 24 April 1924 29 April 1925 Survived the war; scuttled by Royal Navy off Singapore on 11 July 1946; removed from naval ship list on 10 August 1946.

No.5 class Project number I2. 2 vessels were built in 1928 and 1929. Improved model of the No.1-class. In terms of their appearance, their foremast was changed to a tripod-type. Ship Builder Laid down Launched Completed Fate W-5 Mitsui, Tama Shipyard 25 March 1928 30 October 1928 25 February 1929 Sunk by HMS Terrapin at Strait of Malacca on 4 November 1944; removed from naval ship list on 10 March 1945. W-6 Ōsaka Iron Works 10 March 1928 29 October 1928 25 February 1929 Sunk by air raid off Kuching on 26 December 1941; removed from naval ship list on 10 January 1942.

Photos

Footnotes

Bibliography

Ships of the World special issue Vol.45, Escort Vessels of the Imperial Japanese Navy, , (Japan), February 1996 The Maru Special, Japanese Naval Vessels No.50, Japanese minesweepers and landing ships, (Japan), April 1981