The otherwise known as the "Circle Three" Plan was the third 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 ( ''Maru-1'') to build 39 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, such as 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 Evans, ''Kaigun''. page 238-239 In 1934, the Naval Ministry submitted its second expansion plan ''Maru-2'' to 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 ...

, to make up for the shortfall in funding caused by modifications to rectify issues with existing equipment after the

Tomozuru Incident was one of four s of the Imperial Japanese Navy (IJN). It capsized in a storm on 12 March 1934, shortly after its completion. This incident forced the IJN to review the stability of all recently completed, under construction and planned ships. It ...

and IJN 4th Fleet Incident, when it was revealed that the basic designs of many Japanese warships were flawed due to poor construction techniques and instability caused by attempting to mount too much weaponry on too small a displacement hull. In addition, 48 new warships and creation of eight new Naval Air Groups were funded. By 1937, the term of the London Naval Treaty had expired, and the Japanese government refused overtures to participate in further disarmament negotiations. Instead, a massive third expansion plan was 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 1937, calling for 66 new combat vessels, centering on two of the new ''Yamato''-class battleships and two ''Shōkaku''-class aircraft carriers, and expansion of the Imperial Japanese Navy Air Service by 14 more Naval Air Groups. This plan was a multiyear (six year) budget, and allocated a total of 806,549,000

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 ...

was allotted for warship construction and 75,267,000 Yen for

naval aviation Naval aviation is the application of Military aviation, military air power by Navy, navies, whether from warships that embark aircraft, or land bases. Naval aviation is typically projected to a position nearer the target by way of an aircraft ...

. The final three vessels (two ''Katori'' class training cruisers, plus ''Ikino'' supply ship) were funded under the 1938 Supplementary Estimates.

Background

Table of vessels

Notes

References

See also