Japanese submarine I-61

The first unit of the KD4 sub-class, I-61 was built by Mitsubishi at Kobe, Japan. Her keel was laid on 15 November 1926 and she was launched on 12 November 1927. She was completed on 6 April 1929.

Upon completion, I-61 was assigned to the Sasebo Naval District.[3] On 24 April 1929, she and her sister ship, the submarine I-62, combined to form Submarine Division 29,[3][4][5][6] in which I-61 spent her entire career.[3] The division was attached to the Sasebo Naval District.[3]

Submarine Division 29 was reassigned to Submarine Squadron 1 in the 1st Fleet in the Combined Fleet on 1 December 1930.[3] I-61 apparently was decommissioned and placed in reserve on 11 January 1932,[6] and was transferred to the Sasebo Defense Division in the Sasebo Naval District on 10 November 1932,[3] and then to Submarine Squadron 2 in the 2nd Fleet in the Combined Fleet on 15 November 1933.[3] She was recommissioned on 1 June 1934.[3] On 27 September 1934, she departed Ryojun, Manchukuo, in company with I-62 and the submarines I-56, I-57, I-58, I-64, I-65, I-66, and I-67 for a training cruise off Qingdao, China.[3][4][7][8][9][10][11][12][13] The nine submarines completed the cruise with their arrival at Sasebo on 5 October 1934.[3][4][7][8][9][10][11][12][13]

On 7 February 1935, I-61 departed Sasebo in company with the other eight submarines of Submarine Squadron 2 — I-53, I-54, I-55, I-59, I-60, I-62, I-63, and I-64 — for a training cruise in the Kuril Islands.[3][4][10][14][15][16][17][18][19] The cruise concluded with their arrival at Sukumo Bay on 25 February 1935.[3][4][10][14][15][16][17][18][19] The nine submarines departed Sasebo on 29 March 1935 to train in Chinese waters, returning to Sasebo on 4 April 1935.[3][4][10][14][15][16][17][18][19] On 15 November 1935, Submarine Division 29 was reassigned to the Sasebo Defense Squadron in the Sasebo Naval District.[3]

On 1 December 1936, I-61 again was assigned to Submarine Squadron 2 in the 2nd Fleet,[3] and on 15 December 1938 she was reassigned to the Submarine School at Kure.[3] On 11 March 1939, I-61 suffered damage in a collision with the Japanese destroyer Yakaze off Mitajiri, Japan.[3][5] Her Submarine School service ended when she was decommissioned and transferred to the Third Reserve in the Sasebo Naval District;[3] sources claim that this took place both on 15 November 1939[3] and on 20 March 1940.[3][6]

On either 15 April 1940 or 15 November 1940,[3] I-61 was recommissioned, and on 15 November 1940 she was reassigned to Submarine Squadron 5 in the Combined Fleet.[3] On 8 January 1941, she collided with the gunboat Kōshū Maru south of Cape Ashizuki, Japan.[3][5]