The were a class of

escort ship Ocean escort was a type of United States Navy warship. They were an evolution of the World War II destroyer escort types. The ocean escorts were intended as convoy escorts and were designed for mobilization production in wartime or low-cost m ...

s in the service of 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 ...

during

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 World War II by country, vast majority of the world's countries—including all of the great power ...

. The Japanese called them "Type D" coast defence ships, and they were the sixth 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 ...

'' (''Kai'' = sea, ocean, ''Bo'' = defence, ''Kan'' = ship), a name used to denote a multi-purpose vessel. 143 ships were ordered under the 1943-44 Programme, and a further 57 units were planned (but never ordered) under the 1944-45 Programme, for an overal total of 200 ships. However only 67 were completed, with the remainder being cancelled.

Background

The Type D, like the and es, were dedicated to the

anti-aircraft Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based ...

(AA) and anti-submarine role. On 22 April 1943, the Navy General Staff decided a mass production of

s, because of the urgent need to protect the

convoy A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support and can help maintain cohesion within a unit. It may also be used ...

s which were under constant attack. The plan was to build a basic escort ship of around 800 tons, with a simple design for easy construction. The first designs, for "Type A" and "Type B" ''Mikura'' class, still needed too many man-hours for building, so in June 1943, the Navy General Staff planned for a simplified design. The result was the ''Ukuru'' class, and a scaled-down model of the ''Mikura'' class, which became the "Type C" (with diesel engines driving twin screws) and "Type D" (with turbine engines driving a single screw) escort classes.

Design

Because of Japan's deteriorating war situation, the Type D version was a further simplification of the ''Ukuru'' design and were built to the same design as the Type C escort ship. However, due to a shortage of

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-cal ...

s to power both groups of vessels, the Type D were powered by

turbine engine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the direct ...

s. This gave a slight increase in speed, from to , but a reduction in range and endurance, at instead of . The Type D was the only ''Kaibōkan'' type to use turbines. They were smaller by 200 tons than the ''Ukuru''s and engines that propelled them were also smaller, at versus for the ''Ukuru''s. Because of the decrease in engine power, the speed fell from to . The number of guns went from three to two. The number of

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 hydraulic shock. Most depth charges use h ...

s aboard was the same, 120, but the number of depth charge throwers was decreased from 18 to 12 and the depth charge chutes were decreased from two to one. Due to the simplifications of the design, a significant saving was made in construction time. The Type D escorts required approximately 20,000 man-hours each, compared to the 35,000 man-hours of the ''Ukuru''s and the 57,000 man-hours of the ''Mikura''s.

Construction

The design work for the Type D ships started in March 1943, at the same time as for the ''Ukuru'' class. They were built concurrently with the ''Ukuru'' class and Type C vessels. The Type D were given even number designations while the Type C were given odd numbers. The Type D were constructed using prefabricated sections that enabled them to be built in as little as three to four months. The lead ship, ''No.2'' (CD-2) was constructed at

Yokosuka Naval Arsenal was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy, and was located at Yokosuka, Kanagawa prefecture on Tokyo Bay, south of Yokohama. History In 1866, the Tokugawa shogunate government established the ...

laid down Laying the keel or laying down is the formal recognition of the start of a ship's construction. It is often marked with a ceremony attended by dignitaries from the shipbuilding company and the ultimate owners of the ship. Keel laying is one o ...

on 5 October 1943, launched on 30 December 1943, and completed on 28 February 1944. '' CD-198'' was the fastest build, being constructed in only 71 days; she was laid down on 31 December 1944, and completed on 11 March 1945. ''CD-204'' was the last of the class being laid down on 27 February 1945 at the

Nagasaki is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. It became the sole port used for trade with the Portuguese and Dutch during the 16th through 19th centuries. The Hidden Christian Sites in the ...

shipyard of

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 ...

, launched on 14 April 1945, and completed on 14 April 1945.

Service

Most of the Type D escorts were assigned to the Escort Fleet. However, they were not able to stop the American

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

offensive. One drawback was they did not have an effective

fire-control system A fire-control system (FCS) is a number of components working together, usually a gun data computer, a director, and radar, which is designed to assist a ranged weapon system to target, track, and hit a target. It performs the same task as a ...

. They were equipped only with one height rangefinder for the AA guns and were powerless against an air attack. Despite being simple to construct they proved themselves very durable for their size. Of the 22 instances of

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, ...

es striking them, they survived 9 times, with ''CD-30'' being struck and surviving on two separate occasions. Of the seven occasions when they struck mines, only one sank. During the war 68 ships were finished out of the 200 planned; 25 were sunk during the war.

Successes

* was sunk on 24 August 1944 by ''CD-22''. * was probably sunk on 11 November 1944 by ''CD-4''. * may also have been sunk by ''CD-4'' on 4 January 1945, though evidence is unclear. * was probably sunk by ''CD-8'', ''CD-32'', and ''CD-52'' with ''Okinawa'' on 9 April 1945. * was sunk on 19 June 1945 by ''CD-158'' with ''CD-63'', ''CD-75'' and ''CD-207'' and ''Okinawa''. * was rendered unfit for further service by damage from ''CD-22'' with ''CD-33'' and ''CD-29'' on 30 October 1944. * was rendered unfit for further service by damage from ''CD-6'' on 14 November 1944. * was probably sunk by ''CD-38'' which reported having contact with and sinking a US Navy submarine on 19 October 1944 near ''Escolar''s expected position. ''Escolar'' was never heard from again.

Ships in class

Under the

Wartime Naval Armaments Supplement Programme The was the 1943-44 War Programme to fund the armaments expansion plan of the Imperial Japanese Navy (IJN). Background Early 1944, the IJN started building warships for war. The plan did not include any large warships which were suitable for offe ...

, it was proposed to build 300 Type C and 200 Type D escorts. These were assigned the Programme numbers #2401-#2700 for the Type C vessels, with #2701-#2900 for the Type D vessels. In view of the vast number intended, no names were allocated, but only numbers; odd numbers from ''No.1'' upwards were assigned to Type C escorts, while even numbers from ''No.2'' upwards were assigned to Type D escorts. The first 143 of the Type D escorts were authorised under the 1943 Fiscal Year, but just 66 were completed and the others cancelled. The remaining 57 Type D vessels were intended to be built under the 1944 Fiscal Year, but no contracts were ever issued.

Notes

References

* * Worth, Richard, ''Fleets of World War II'', Da Capo Press (2001), * Conway's ''All the World's Fighting Ships 1922-1946'' (1980)

External links

Type D class combinedfleet.com
(Retrieved 14 July 2009)

* (Retrieved 14 July 2009) {{WWII Japanese ships Type D escort ships Escort ship classes Escort ships of the Imperial Japanese Navy Ships of the Republic of China Navy Ships of the People's Liberation Army Navy