The were a class of ''

kaibōkan or coastal defense ship was a type of naval ship used by the Imperial Japanese Navy during World War II for escort duty and coastal defense. The term escort ship was used by the United States Navy to describe this category of Japanese ships. ...

'' (equivalent to US

destroyer escort Destroyer escort (DE) was the United States Navy mid-20th-century classification for a warship designed with the endurance necessary to escort mid-ocean convoys of merchant marine ships. Development of the destroyer escort was promoted by th ...

s or British

frigates A frigate () is a type of warship. In different eras, the roles and capabilities of ships classified as frigates have varied somewhat. The name frigate in the 17th to early 18th centuries was given to any full-rigged ship built for speed and ...

) built for the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...

just prior to

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. Four ships out of an initially planned 16 vessels were completed. The class was also referred to by internal Japanese documents as the .

Background

The ''Shimushu''-class ''

'', as with the torpedo boat, was a consequence of the 1930

London Naval Treaty The London Naval Treaty, officially the Treaty for the Limitation and Reduction of Naval Armament, was an agreement between the United Kingdom, Japan, France, Italy, and the United States that was signed on 22 April 1930. Seeking to address is ...

, which placed limitations on the total destroyer tonnage the Imperial Japanese Navy was permitted. One way in which the treaty could be circumvented was to use a loophole in the treaty which permitted ships of between 600 and 2,000 tons, with no more than four guns over 76mm, no torpedoes, and with a maximum speed of no more than 20 knots. A new class of vessel was designed to use this loophole, and was given the obsolete designation of ''kaibōkan'' (''Kai'' = sea, ocean, ''Bo'' = defence, ''Kan'' = ship), which had previously been used to designate obsolete warships which had been reassigned to coastal defense duties. However, due to many other priorities, the budget for this new class was not secured until the 1937

3rd Naval Armaments Supplement Programme The otherwise known as the "Circle Three" Plan was the third of four expansion plans of the Imperial Japanese Navy between 1930 and the start of World War II. Background The London Naval Treaty placed severe restrictions on Japan's naval capabili ...

Design

Due to the low priority of the project, the design of the ''Shimushu''-class was subcontracted out to a private firm,

Mitsubishi Heavy Industries is a Japanese multinational engineering, electrical equipment and electronics corporation headquartered in Tokyo, Japan. MHI is one of the core companies of the Mitsubishi Group and its automobile division is the predecessor of Mitsubishi Mo ...

. The Imperial Japanese Navy had intended for a simple design whose primary role was patrol and fisheries protection of the remote and sub-Arctic

Kurile Islands The Kuril Islands or Kurile Islands (; rus, Кури́льские острова́, r=Kuril'skiye ostrova, p=kʊˈrʲilʲskʲɪjə ɐstrɐˈva; Japanese: or ) are a volcanic archipelago currently administered as part of Sakhalin Oblast in the ...

, which would free destroyers currently used for this role for higher priority missions. The secondary role of the new class was to be

minesweeping Minesweeping is the practice of the removal of explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that ...

, and convoy escort was considered a minor third priority. However, the design developed by Mitsubishi was more complex than the Imperial Japanese Navy had anticipated, with a double-curved bow and a forecastle deck which improved seaworthiness in the rough northern seas. The hull was also reinforced and insulated against the cold weather. The consequence was that the design was not suited to prefabrication or mass production, and construction times which created problems when more vessels were needed in a short time after the start of the

Pacific War The Pacific War, sometimes called the Asia–Pacific War, was the theater of World War II that was fought in Asia, the Pacific Ocean, the Indian Ocean, and Oceania. It was geographically the largest theater of the war, including the vast ...

. The ships measured

overall Overalls, also called bib-and-brace overalls or dungarees, are a type of garment usually used as protective clothing when working. The garments are commonly referred to as a "pair of overalls" by analogy with "pair of trousers". Overalls were ...

, with a

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

of and a

draft Draft, The Draft, or Draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a vessel ...

of .Chesneau, p. 205 They displaced at

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

load and at deep load. The ships had two

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...

s, each driving one

propeller shaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power and torque and rotation, usually used to connect ...

, which were rated at a total of for a speed of . The ships had a range of at a speed of .Jentschura, Jung & Mickel, p. 186 The ''Shimushu''-class was well armed for its size. The main armament of the ''Shimushu'' class consisted of three Type 3 guns in single mounts, one

superfiring Superfiring armament is a naval military building technique in which two (or more) turrets are located in a line, one behind the other, with the second turret located above ("super") the one in front so that the second turret can fire over the ...

pair aft and one mount forward of the

superstructure A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships. Aboard ships and large boats On water craft, the superstruct ...

, which had been taken from old destroyers. The minesweeping role was accomplished by two paravanes on each beam. The ASW role was accomplished with 18 Type 95

depth charge A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive Shock factor, hydraulic shock. Most depth ...

s, but this was doubled in May 1942 when the minesweeping gear was removed and a Type 93 sonar was installed. The anti-submarine weaponry later rose to 60 depth charges with a Type 97 trench mortar and six depth charge throwers. Anti-aircraft protection was by four Type 96 anti-aircraft guns in two twin-gun mounts abreast the bridge. This was later increased by August 1943 when the twin-mounts were replaced by triple-mounts, and an additional three triple-mounts, one in front of the bridge and two behind the smokestack were added. A Type 22 radar was also installed in 1943 and a Type 13 in 1944.

Operational service

Despite being designed for operations in northern waters, the

lead vessel The lead ship, name ship, or class leader is the first of a series or class of ships all constructed according to the same general design. The term is applicable to naval ships and large civilian vessels. Large ships are very complex and may ...

of the class, was used primarily in southern waters for convoy escort. She survived the war and was given as a

prize of war A prize of war is a piece of enemy property or land seized by a belligerent party during or after a war or battle, typically at sea. This term was used nearly exclusively in terms of captured ships during the 18th and 19th centuries. Basis in inte ...

to the Soviet Navy, which continued to use her until 1959. was sunk by a submarine in 1944. and served in the northern Pacific, and both were scrapped after the end of the war.

Ships in class

The four ships were ordered as ships #9 to #12 under the

in 1937.

Notes

References

* * *

External links

Shimushu class at Imperial Japanese Navy.com
{{Mitsui Engineering & Shipbuilding, state=autocollapse

Shimushu russian: Шумшу ja, 占守島 , image_name = Shumshu.jpg , image_caption = A Landsat 7 image of Shumshu Island. The northern tip of Paramushir Island is at left. The First Kuril Strait lies across the upper portion of the image. , image_size ...