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The , otherwise known as the "Circle One" plan was the first of four expansion plans 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 ...
between 1930 and the start of
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 ...
.


Background

The London Naval Treaty placed severe restrictions on Japan's naval capabilities vis-a-vis the
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
and the British
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by Kingdom of England, English and Kingdom of Scotland, Scottish kings from the early medieval period, the first major maritime engagements were foug ...
in terms of tonnage and numbers of capital warships. The response of the
Imperial Japanese Navy General Staff The was the highest organ within the Imperial Japanese Navy. In charge of planning and operations, it was headed by an Admiral headquartered in Tokyo. History Created in 1893, the Navy General Staff took over operational (as opposed to adminis ...
was to initiate a construction program to build new warships to the allotted tonnage limits in each of the restricted categories, and to invest in types of warships and weaponry not specifically covered by the provisions of the treaty. The "Circle One" plan was submitted by the Naval Ministry and approved by the
Cabinet Cabinet or The Cabinet may refer to: Furniture * Cabinetry, a box-shaped piece of furniture with doors and/or drawers * Display cabinet, a piece of furniture with one or more transparent glass sheets or transparent polycarbonate sheets * Filing ...
in November 1930, and officially ratified by the
Diet of Japan The is the national legislature of Japan. It is composed of a lower house, called the House of Representatives (, ''Shūgiin''), and an upper house, the House of Councillors (, '' Sangiin''). Both houses are directly elected under a paral ...
in 1931. It called for the construction of 39 new combat vessels, centering on four of the new s, and expansion of the
Imperial Japanese Navy Air Service The was the air arm of the Imperial Japanese Navy (IJN). The organization was responsible for the operation of naval aircraft and the conduct of aerial warfare in the Pacific War. The Japanese military acquired their first aircraft in 1910 ...
to 14 Naval Air Groups. Budget for the construction of the warships was on a six-year basis, and the budget for forming the air groups was on a three-year basis. Total funding allotted was 247,080,000
Yen The is the official currency of Japan. It is the third-most traded currency in the foreign exchange market, after the United States dollar (US$) and the euro. It is also widely used as a third reserve currency after the US dollar and the ...
for ship construction and 44,956,000 Yen for naval aviation expansion. In terms of naval aviation development, the "Circle One" plan also concentrated on the development of new aircraft technologies, especially large
seaplane A seaplane is a powered fixed-wing aircraft capable of takeoff, taking off and water landing, landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their tec ...
s, land-based
bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...
s, as well as carrier-based attack aircraft and
floatplane A floatplane is a type of seaplane with one or more slender floats mounted under the fuselage to provide buoyancy. By contrast, a flying boat uses its fuselage for buoyancy. Either type of seaplane may also have landing gear suitable for land, ...
attack aircraft that could be launched from battleships, cruisers or submarines. Attention was also given to training of pilots and air crews in
dive bombing A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target simplifies the bomb's trajectory and allows the pilot to keep visual contact throughou ...
and
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, s ...
tactics Tactic(s) or Tactical may refer to: * Tactic (method), a conceptual action implemented as one or more specific tasks ** Military tactics Military tactics encompasses the art of organizing and employing fighting forces on or near the battlefiel ...
.Evans, ''Kaigun'', page 249 In a 1932 supplement to the Circle One plan, additional funding was added for the construction of three more vessels: the
submarine tender A submarine tender is a type of depot ship that supplies and supports submarines. Development Submarines are small compared to most oceangoing vessels, and generally do not have the ability to carry large amounts of food, fuel, torpedoes, and ...
''Taigei'', and two
submarine chaser A submarine chaser or subchaser is a small naval vessel that is specifically intended for anti-submarine warfare. Many of the American submarine chasers used in World War I found their way to Allied nations by way of Lend-Lease in World War I ...
s.


Table of vessels


See also

*
2nd Naval Armaments Supplement Programme The otherwise known as the "Circle Two" Plan was the second 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 capab ...
(Maru 2 Keikaku, 1934) *
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 ...
(Maru 3 Keikaku, 1937) *
4th Naval Armaments Supplement Programme The was one of the armaments expansion plan of the Imperial Japanese Navy (IJN). Background In 1939, the IJN started new naval armaments expansion plan. It extended to 80 warships and 75 Naval Air Groups by 1.6 billion JPY. Table of vessels No ...
(Maru 4 Keikaku, 1939) *
Temporal Naval Armaments Supplement Programme The is one of the armaments expansion plan of the Imperial Japanese Navy (IJN). Background In October 1940, the IJN schemed building of the submarines and auxiliary vessels because there was a shortage of them. Table of vessels See also *1st N ...
(Maru Rin Keikaku, 1940) * Rapidly Naval Armaments Supplement Programme (Maru Kyū Keikaku, 1941) *
Additional Naval Armaments Supplement Programme The was one of the naval expansion plans of the Imperial Japanese Navy (IJN). Background In November 1941, the IJN required many additional submarines for the Pacific War, as a pressing matter. To meet this need, the IJN negotiated with the Minist ...
(Maru Tui Keikaku, 1941) *
5th Naval Armaments Supplement Programme Fifth is the ordinal form of the number five. Fifth or The Fifth may refer to: * Fifth Amendment to the United States Constitution, as in the expression "pleading the Fifth" * Fifth column, a political term * Fifth disease, a contagious rash that ...
(Maru 5 Keikaku, 1941) *
6th Naval Armaments Supplement Programme 6 (six) is the natural number following 5 and preceding 7. It is a composite number and the smallest perfect number. In mathematics Six is the smallest positive integer which is neither a square number nor a prime number; it is the second small ...
(Maru 6 Keikaku, 1942) *
Modified 5th Naval Armaments Supplement Programme The was one of the wartime armaments expansion plans of the Imperial Japanese Navy (IJN). Background In September 1942, after being defeated in the Battle of Midway, the IJN drew up a new armaments expansion plan. This plan was combined by the 5 ...
(Kai-Maru 5 Keikaku, 1942) *
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 ...
(Maru Sen Keikaku, 1944)


Notes


References

* {{DEFAULTSORT:Naval Armaments Supplement Programme Imperial Japanese Navy Naval history of Japan