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{{Short description|Second of four Imperial Japanese Naval Expansion plans}}
[[File:Japanese heavy cruiser Chikuma.jpg|thumb|right|250px|Construction of the cruiser {{ship|Japanese cruiser|Tone|1937|2}} was authorized under the "Circle-2 Plan"]]

The {{nihongo|'''2nd Naval Armaments Supplement Programme'''|マル2計画, 第二次補充計画|Maru 2 Keikaku, Dai-Ni-Ji Hojū Keikaku}}  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 capabilities vis-a-vis the [[United States Navy]] and the British [[Royal Navy]] in terms of tonnage and numbers of [[capital ship|capital warships]]. The response of the [[Imperial Japanese Navy General Staff]] 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.<ref>Evans, ''Kaigun''. pp. 238–239</ref>

The "Circle One" plan was submitted by the [[Ministry of the Navy of Japan|Naval Ministry]] and approved by the [[Cabinet of Japan|Cabinet]] in November 1930, and officially ratified by the [[Diet of Japan]] in 1931. It called for the construction of 39 new combat vessels, centering on four of the new {{Sclass|Mogami|cruiser}}s, and expansion of the [[Imperial Japanese Navy Air Service]] to 14 Naval Air Groups. However, plans for a second expansion budget were delayed by the [[Tomozuru Incident|''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. As a result, most of the naval budget in 1932–1933 was absorbed in modifications to rectify issues with existing equipment.

In 1934, the Naval Ministry submitted its second expansion plan to the Cabinet and Diet for approval. This plan was a multiyear (four year) budget, covering the construction of 48 new warships and creation of eight new Naval Air Groups. A total of 431,680,800 [[Yen]] was allotted for warship construction and 33,000,000 Yen for [[naval aviation]].

==Table of vessels==
{| class="wikitable" width="90%"
! width="8%" | Category
! width="10%" | Class
! width="2%" | Planned
! width="15%" | Completed
! width="10%" | Converted
!width="6%" | Cancelled
|-
| Heavy cruiser
| {{Sclass|Tone|cruiser|5}}
| 2
| {{ship|Japanese cruiser|Tone|1937|2}}, {{ship|Japanese cruiser|Chikuma|1938|2}}
| Converted to heavy cruiser.
|
|-
| rowspan="2"| Aircraft carrier
| ''Sōryū''
| 1
| {{ship|Japanese aircraft carrier|Sōryū||2}}
| One planned vessel was converted to ''Hiryū'' instead.
| 
|-
| ''Hiryū''
| 1
| {{ship|Japanese aircraft carrier|Hiryū||2}}
| 
| 
|-
| rowspan="2"|Destroyer
| {{Sclass|Shiratsuyu|destroyer|5}}
| 4
| {{Ship|Japanese destroyer|Umikaze|1936|2}}, {{ship|Japanese destroyer|Yamakaze|1936|2}}, {{ship|Japanese destroyer|Kawakaze|1936|2}}, {{ship|Japanese destroyer|Suzukaze||2}}
| 
| 
|-
| {{Sclass|Asashio|destroyer|5}}
| 10
| ''[[Japanese destroyer Asashio (1936)|Asashio]]'', ''[[Japanese destroyer Ōshio|Ōshio]]'', ''[[Japanese destroyer Michishio|Michishio]]'', ''[[Japanese destroyer Arashio|Arashio]]'', ''[[Japanese destroyer Yamagumo (1937)|Yamagumo]]'', ''[[Japanese destroyer Natsugumo (1937)|Natsugumo]]'', ''[[Japanese destroyer Asagumo (1938)|Asagumo]]'', ''[[Japanese destroyer Minegumo (1937)|Minegumo]]'', ''[[Japanese destroyer Arare (1937)|Arare]]'', ''[[Japanese destroyer Kasumi (1937)|Kasumi]]''
| 
| 
|-
| Torpedo boat
| {{Sclass|Ōtori|torpedo boat|5}}
| 16
| ''[[Japanese torpedo boat Ōtori (1935)|Ōtori]]'', ''[[Japanese torpedo boat Hiyodori|Hiyodori]]'', ''[[Japanese torpedo boat Hayabusa (1935)|Hayabusa]]'', ''[[Japanese torpedo boat Kasasagi (1935)|Kasasagi]]'', ''[[Japanese torpedo boat Kiji (1937)|Kiji]]'', ''[[Japanese torpedo boat Kari (1937)|Kari]]'', ''[[Japanese torpedo boat Sagi (1937)|Sagi]]'', ''[[Japanese torpedo boat Hato (1937)|Hato]]''
| 
| 8 vessels were cancelled.
|-
| Cruiser submarine
| ''[[Junsen type submarine#Junsen III (I-7 class)|I-7]]''
| 2
| {{Jsub|I-7||2}}, {{Jsub|I-8||2}}
| 
| 
|-
| Large sized submarine
| ''[[Kaidai-class submarine#Kaidai VIa/b (I-168 class and I-174 class)|I-74]]''
| 2
| ''[[Japanese submarine I-174|I-74]]'', ''[[Japanese submarine I-175|I-75]]''
| 
| 
|-
| Seaplane tender Type-A (10,000-ton class)
| ''Chitose''
| 2
| {{ship|Japanese aircraft carrier|Chitose||2}}, {{ship|Japanese aircraft carrier|Chiyoda||2}}
| 
| 
|-
| Seaplane tender Type-B (9,000-ton class)
| ''Mizuho''
| 1
| {{ship|Japanese seaplane carrier|Mizuho||2}}
| 
| 
|-
| Submarine chaser
| ''[[No.1-class submarine chaser|No.3]]''
| 1
| {{ship|Japanese submarine chaser|No.3||2}}
| 
| 
|-
| Submarine chaser (Small: diesel)
| ''[[No.251-class auxiliary submarine chaser|No.51]]''
| 2
| ''[[Japanese auxiliary submarine chaser No.251|No.51]]'', ''[[Japanese auxiliary submarine chaser No.252|No.52]]''
| 
| 
|-
| Submarine chaser (Small: turbine)
| ''[[No.251-class auxiliary submarine chaser|No.53]]''
| 1
| ''[[Japanese auxiliary submarine chaser No.253|No.53]]''
| 
| 
|-
| Fleet oiler
| ''Tsurugizaki''
| 2
| ''[[Japanese aircraft carrier Shōhō|Tsurugizaki]]'', ''[[Japanese aircraft carrier Zuihō|Takasaki]]''
| Both converted into [[Zuihō-class aircraft carrier|Shōhō-class aircraft carriers]] prior to the war, in which both were lost. 
| 
|-
| Repair ship
| ''Akashi''
| 1
| {{ship|Japanese repair ship|Akashi||2}}
| 
| 
|-
|}

==See also==
* [[1st Naval Armaments Supplement Programme (Japan, 1931)|1st Naval Armaments Supplement Programme]] (Maru 1 Keikaku, 1931)
* [[3rd Naval Armaments Supplement Programme (Japan, 1937)|3rd Naval Armaments Supplement Programme]] (Maru 3 Keikaku, 1937)
* [[4th Naval Armaments Supplement Programme (Japan, 1939)|4th Naval Armaments Supplement Programme]] (Maru 4 Keikaku, 1939)
* [[Temporal Naval Armaments Supplement Programme (Japan, 1940)|Temporal Naval Armaments Supplement Programme]] (Maru Rin Keikaku, 1940)
* [[Rapidly Naval Armaments Supplement Programme (Japan, 1941)|Rapidly Naval Armaments Supplement Programme]] (Maru Kyū Keikaku, 1941)
* [[Additional Naval Armaments Supplement Programme (Japan, 1941)|Additional Naval Armaments Supplement Programme]] (Maru Tui Keikaku, 1941)
* [[5th Naval Armaments Supplement Programme (Japan, 1941)|5th Naval Armaments Supplement Programme]] (Maru 5 Keikaku, 1941)
* [[6th Naval Armaments Supplement Programme (Japan, 1942)|6th Naval Armaments Supplement Programme]] (Maru 6 Keikaku, 1942)
* [[Modified 5th Naval Armaments Supplement Programme (Japan, 1942)|Modified 5th Naval Armaments Supplement Programme]] (Kai-Maru 5 Keikaku, 1942)
* [[Wartime Naval Armaments Supplement Programme (Japan, 1944)|Wartime Naval Armaments Supplement Programme]] (Maru Sen Keikaku, 1944)

==Notes==
{{reflist}}

==References==
*{{cite book
 | last = Evans 
 | first = David 
 | year = 1979
 | title = Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887-1941 
 | publisher = US Naval Institute Press 
 | location = 
 | isbn = 0-87021-192-7
}}

{{IJN Naval Armnament Supplement Programs}}

[[Category:Imperial Japanese Navy|Naval Armaments Supplement Programme]]
[[Category:Naval history of Japan|Naval Armaments Supplement Programme]]