Ukuru-class escort ship

The Ukuru-class escort ships (鵜来型海防艦, Ukuru-gata kaibōkan) were a class of twenty-nine kaibōkan escort vessels built for the Imperial Japanese Navy during World War II.[1] The class was also referred to by internal Japanese documents as the "Modified B-class" coastal defense vessel (改乙型海防艦, Kai-Otsu-gata kaibōkan), and they were the fourth class of kaibōkan.

Uku in 1944
Class overview
Name: Ukuru class
Operators:
Preceded by: Mikura class
Succeeded by:

Type C

Type D
Built: 1942–1944
In commission: 1943–1964
Planned: 142
Completed: 20
Cancelled: 2
Lost: 10
General characteristics
Type: Escort vessel
Displacement: 940 long tons (955 t) standard
Length: 77.7 m (255 ft) 258.4
Beam: 9.1 m (29 ft 10 in) 29.10
Draught: 3.05 m (10 ft) 10
Propulsion: 2 shaft, geared diesel engines, 4,400 hp (3,281 kW)
Speed: 19.5 knots (22.4 mph; 36.1 km/h)
Range: 5,000 nmi (9,300 km) at 16 kn (18 mph; 30 km/h)
Complement: 150
Sensors and
processing systems:
  • Type 22 and 13 radars
  • Type 93 and/or Type 3 sonar
Armament:

Background

The Mikura class escort ship was developed after the start of the Pacific War, it became apparent that a design more capable of anti-submarine warfare than the previous Shimushu and Etorofu class kaibōkan was needed. Despite being a simplified design, the Mikura-class vessels still took too long to construct, and due to the high attrition of Japan's destroyer and escort ships, action needed to be urgently taken to produce more ships in a quicker time. Furthermore, operational experience had shown that the Mikura-class was still very weak in its anti-aircraft capability. The first five of the new Ukuru-class was authorized under the 1941 Rapid Naval Armaments Supplement Programme and an additional six in the 1942 Modified 5th Naval Armaments Supplement Programme and nine under the 1944 Wartime Naval Armaments Supplement Programme. Twenty vessels were completed; two more lay uncompleted by war’s end. In addition, nine units and two additional unfinished ships belong to a sub-class called the Hiburi[2]

Description

The Ukuru-class was a further simplification of the Mikura design. The hull was constructed using prefabricated sections which avoided the use of shaped steel or curved plates, which greatly reduced construction time. The curved plates on the bridge were also eliminated, and the smoke stacks were made of hexagonal elements instead of with a circular or oval cross-section. Internally, individual crew quarters were eliminated, becoming a communal area, and overall the construction was very spartan. These changes reduced construction time to under four months, although construction was often hindered by the lack of diesel engines.[2]

The main battery was the same as on the Mikura-class, with three dual-purpose Type 10 120 mm AA guns one forward, and a twin mount aft, but the later ships in the class were fitted with modified gun shields. Anti-aircraft protection was by five triple-mount Type 96 25-millimeter (1.0 in) anti-aircraft guns with two abreast the bridge, one of each side of the smokestack, and one aft on the deck house, along with a single-mount in front of the bridge. Some units received additional single-mount Type 96s, which were located on the forecastle. The Ukuru-class was equipped with the Type 22 and Type 13 radar. The Ukuru class was initially armed with 120 depth charges with two Type 94 depth charge projectors, sixteen Type 3 depth charge throwers and two depth charge chutes at the stern. The ships were provided with a Model 93 sonar and a Type 93 hydrophone; later units received the Type 3 Model 2 sonar, and some would later receive an 8 cm (3 in) trench mortar. [2]

Initially, the class retained capacity as a minesweeper, and was equipped with two paravanes; however, this was removed soon after completion.[2]

Operational service

Despite being easy to build, they proved quite durable, with 11 occurrences of the class striking mines and only 3 sinking, one of which was after the war. Ikuna survived being torpedoed by USS Crevalle and striking a mine as well.

The Ukuru vessels were used extensively on convoy escort assignment in the South China Sea and East China Sea, where they frequently were attacked by Allied submarines or aircraft. However, despite their durability, they proved to be relatively ineffective against Allied submarines. Okinawa was the most successful ship of the class, helping to sink two US submarines, USS Snook on April 14, 1945 with the kaibōkan CD-8, CD-32, and CD-52; and USS Bonefish on June 19, 1945 with kaibokan CD-63, CD-75, CD-158, and CD-207.

Surviving ships were used in the immediate postwar period as minesweepers and for repatriation. Five vessels survived to return to Japanese control, and were used as weather survey ships or as patrol ships, with the last being retired in 1966.[2]

Ships

  • Ukuru (鵜来), constructed at Nihon Kokan, Tsurumi, laid down on October 9, 1943, launched on May 15, 1944, and commissioned on July 31, 1944. Ukuru survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sold for scrapping on November 24, 1965. Her hull number PL104 is seen in a scene in the 1961 classic Japanese movie "Mothra".
  • Hiburi (日振), constructed at Hitachi, Sakurajima, laid down on January 3, 1944, launched on April 10, 1944, and commissioned on June 27, 1944. Hiburi was torpedoed and sunk by USS Harder on August 22, 1944 with 154 killed and wounded.
  • Shonan (昭南), constructed at Hitachi, Sakurajima, laid down on February 23, 1944, launched on May 19, 1944, and commissioned on July 13, 1944. Shonan was torpedoed and sunk by USS Hoe on February 25, 1945 with 198 crew and passengers killed.
  • Daito (大東), constructed at Hitachi, Sakurajima, laid down on February 23, 1944, launched on June 24, 1944, and commissioned on August 7, 1944. Daito survived the war, but was lost while minesweeping shortly after the war ended on November 16, 1945.
  • Okinawa (沖縄), constructed at Nihon Kokan, Tsurumi, laid down on December 10, 1943, launched on June 19, 1944, and commissioned on August 16, 1944. Okinawa was damaged by a bomb in an air attack by P-38s while escorting TA no. 2 on November 5, 1944 and damaged by PT boats on November 9 and by aircraft again on November 18, 1944. Okinawa was sunk on July 30, 1945 by aircraft from HMS Formidable.
  • Kume (久米), constructed at Hitachi, Sakurajima, laid down on May 26, 1944, launched on August 15, 1944, and commissioned on September 25, 1944. Kume was torpedoed and sunk by USS Spadefish with the loss of 89 men.
  • Ikuna (生名), constructed at Hitachi, Sakurajima, laid down on June 30, 1944, launched on September 4, 1944, and commissioned on October 15, 1944. Ikuna was hit by a torpedo by USS Crevalle and damaged on April 10, 1945. On August 1, she struck a mine and was damaged. Ikuna survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sold for scrapping on May 25, 1963.
  • Shinnan (新南), constructed at Uraga dock, laid down on June 30, 1944, launched on September 4, 1944, and commissioned on October 21, 1944. Shinnan survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sent to the petrol development agency in October 1967. She was scrapped in 1975.
  • Yaku (屋久), constructed at Uraga dock, laid down on June 30, 1944, launched on September 4, 1944, and commissioned on October 23, 1944. Yaku was torpedoed and sunk by USS Hammerhead with the loss of 132 men.
  • Aguni (粟国), constructed at Nihon Kokan, Tsurumi, laid down on February 15, 1944, launched on September 21, 1944, and commissioned on December 2, 1944. On May 27, 1945, Aguni was damaged by a Bat glide bomb. The bomb's 1,000-lb warhead exploded off Aguni's starboard bow demolishing the whole foredeck area ahead of the bridge and killing 33 sailors. After being hit, Aguni's crew had to cut her anchor chain to free her. Kaibokan CD-12 was dispatched to assist Okinawa in rescuing Aguni’s crew, but despite the heavy damage the kaibokan remains navigable and proceeds stern first to Pusan, Korea on her own power. Aguni survived the war and was sold for scrapping on May 20, 1948.
  • Mokuto (目斗), constructed at Hitachi, Sakurajima, laid down on November 5, 1944, launched on January 7, 1945, and commissioned on February 19, 1945. On April 4, 1945, Mokuto struck a mine and sank.
  • Inagi (稲木), constructed at Mitsui, Tamano, laid down on May 15, 1944, launched on September 25, 1944, and commissioned on December 16, 1944. Inagi was bombed and sunk by planes from HMS Formidable on August 9, 1945 with the loss of 29 killed and 35 wounded.
  • Uku (宇久), constructed at Sasebo Navy Yard, laid down on August 1, 1944, launched on November 12, 1944, and commissioned on December 30, 1944. Uku struck a mine on 9 April 1945 and was damaged. She survived the war and was ceded to the United States as a war reparation and later scrapped.
  • Chikubu (竹生), constructed at Uraga dock, laid down on September 8, 1944, launched on November 24, 1944, and commissioned on December 31, 1944. Chikubu survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being sold for scrapping on October 4, 1962.
  • Habushi (羽節), constructed at Mitsui, Tamano, laid down on August 20, 1944, launched on November 20, 1944, and commissioned on January 10, 1945. Habushi struck a mine on April 8, 1945 and was damaged. She survived the war and was ceded to the United States as a war reparation and scrapped starting October 17, 1947.
  • Sakito (崎戸), constructed at Hitachi, Sakurajima, laid down on September 7, 1944, launched on November 29, 1944, and commissioned on January 10, 1945. On June 27, 1945, Sakito struck a mine and was damaged. Sakito survived the war and was scrapped on December 1, 1947.
  • Kuga (久賀), constructed at Sasebo Navy Yard, laid down on August 1, 1944, launched on November 19, 1944, and commissioned on January 25, 1945. Kuga struck a mine on June 25, 1945 and was damaged. She survived the war and was scrapped on June 30, 1947.
  • Ojika (男鹿), constructed at Mitsui, Tamano, laid down on September 7, 1944, launched on December 30, 1944, and commissioned on February 21, 1945. Ojika was torpedoed and sunk by USS Springer on June 2, 1945.
  • Kozu (神津), constructed at Uraga dock, laid down on October 20, 1944, launched on December 31, 1944, and commissioned on February 7, 1945. She survived the war and was ceded to the Soviet Union as a war reparation on August 28, 1947. Served in Soviet Pacific Ocean Fleet as patrol ship EK-47 (1947), oceanographic research ship Nord (1948), later - Glubomer (1953), repair ship PM-62 (1955). Decommissioned on January 25, 1969 and scrapped.
  • Kanawa (金輪), constructed at Mitsui, Tamano, laid down on November 15, 1944, and commissioned on March 25, 1945. Kanawa survived the war and was ceded to the UK as a war reparation and scrapped on August 14, 1947.
  • Shiga (志賀), constructed at Sasebo Navy Yard, laid down on November 25, 1944, launched on February 9, 1945, and commissioned on March 20, 1945. Shiga survived the war and later became a weather survey ship in the Japanese Maritime Transport Bureau before being discarded on May 6, 1964. Her hull became the pavilion for Maritime Amusement Park in Chiba City, but her hull deteriorated because of poor maintenance and was dismantled and scrapped in 1998.[3]
  • Amami (奄美), constructed at Nihon Kokan, Tsurumi, laid down on February 14, 1944, launched on November 30, 1944, and commissioned on April 8, 1945. Amami survived the war and was ceded to the UK as a war reparation and scrapped on December 20, 1947.
  • Hodaka (保高), constructed at Uraga dock, laid down on November 27, 1944, launched on January 28, 1945, and commissioned on March 30, 1945. She survived the war and was ceded to the United States as a war reparation and scrapped starting March 1, 1948.
  • Habuto(波太), constructed at Hitachi, Sakurajima, laid down on December 3, 1944, launched on February 28, 1945, and commissioned on April 7, 1945. Habuto struck a mine on June 6, 1945 and was damaged. She struck a second mine on June 10, 1945 and was again damaged. She survived the war and was ceded to the UK as a war reparation and scrapped on July 16, 1947.
  • Iwo (伊王), constructed at Maizuru Navy Yard, laid down on November 25, 1944, launched on February 12, 1945, and commissioned on March 24, 1945. Iwo struck a mine on June 13, 1945 and was damaged. She was damaged lightly in an air attack by planes from USS Shangri-La, losing 4 killed and 61 wounded. She survived the war and was scrapped starting July 2, 1948.
  • Takane (高根), constructed at Mitsui, Tamano, laid down on December 15, 1944, launched on February 13, 1945, and commissioned on April 26, 1945. Takane survived the war and was scrapped starting November 27, 1947.
  • Ikara (伊唐), constructed at Uraga dock, laid down on December 26, 1944, launched on February 22, 1945, and commissioned on April 30, 1945. On August 9, 1945, Ikara struck a mine and sank.
  • Shisaka (四阪), constructed at Hitachi, Sakurajima, laid down on August 21, 1944, launched on October 31, 1944, and commissioned on December 15, 1944. She survived the war and was ceded to the ROCN war reparation and named as Huai An (惠安), but later was captured by the Chinese communists at the end of Chinese Civil War, and entered PLAN under the same name. The ship was later renamed as Rui Jin (瑞金) and served as a training ship in PLAN until the early 1980s before it as finally scrapped.
  • Ikuno (生野), constructed at Uraga dock, laid down on January 3, 1945, launched on March 11, 1945, and commissioned on July 17, 1945. She survived the war and was ceded to the Soviet Union as a war reparation on July 29, 1947. Served in Soviet Pacific Ocean Fleet as patrol ship EK-41 (1947), target ship TsL-41 (1948), oceanographic research ship Val (1949). Decommissioned on June 1, 1961 and scrapped.

See also

Notes

  1. Worth p. 208
  2. Stille, Mark (2017). Imperial Japanese Navy Antisubmarine Escorts 1941–45. Oxford, UK: Osprey Publishing. p. 30-33. ISBN 978 1 4728 1817 1.

References

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