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, Potsdam Declaration, when it was dissolved followin ...

between 1930 and the start of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

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 naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

and the British

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

in terms of tonnage and numbers of capital warships. The response of the Imperial Japanese Navy General Staff 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 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, to make up for the shortfall in funding caused by modifications to rectify issues with existing equipment after the Tomozuru Incident 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 , transcription_name = ''Kokkai'' , legislature = 215th Session of the National Diet , coa_pic = Flag of Japan.svg , house_type = Bicameral , houses = , foundation=29 November 1890(), leader1_type ...

in 1937, calling for 66 new combat vessels, centering on two of the new ''Yamato''-class

battleship A battleship is a large, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...

s and two ''Shōkaku''-class

aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...

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

naval aviation Naval aviation / Aeronaval is the application of Military aviation, military air power by Navy, navies, whether from warships that embark aircraft, or land bases. It often involves ''navalised aircraft'', specifically designed for naval use. Seab ...

. 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