I-121-class submarine

I-121 (as I-21) in 1930.
Class overview
Name	I-121 class submarine
Builders	Kawasaki Corporation
Operators	Imperial Japanese Navy
Built	1924–1928
In commission	1927–1945
Planned	6
Completed	4
Cancelled	2
Lost	3
Retired	1
General characteristics
Type	Minelaying submarine
Displacement	1,142 long tons (1,160 t) surfaced 1,768 long tons (1,796 t) submerged
Length	85.20 m (279 ft 6 in) overall
Beam	7.52 m (24 ft 8 in)
Draft	4.42 m (14 ft 6 in)
Propulsion	2 × Rauschenbach Mk.1 diesels 2,400 bhp surfaced 1,100 shp submerged 2 shafts
Speed	14.9 knots (27.6 km/h) surfaced 6.5 knots (12.0 km/h) submerged
Range	10,500 nmi (19,400 km) at 8 knots (15 km/h) surfaced 40 nmi (74 km) at 4.5 knots (8.3 km/h) submerged
Test depth	75 m (246 ft)
Complement	51
Armament	2 × 533 mm (21 in) torpedo tubes 12 × 6th Year Type torpedoes 1 × 14 cm/40 11th Year Type naval gun 42 × naval mines

The I-121-class submarine (伊百二十一型潜水艦, I-hyaku-ni-jū-ichi-gata sensuikan) was a class of submarine in the Imperial Japanese Navy (IJN), serving from the 1920s to the Second World War. The IJN classed it as a Kiraisen type submarine (機雷潜型潜水艦, Kiraisen-gata sensuikan). The type name, was shortened to Kirai Fusetsu Sensuikan (機雷敷設潜水艦, Minelaying submarine).

Construction

The Empire of Japan received six U-boats as a reparation payment after World War I. The IJN copied U-125 and designed the I-21 class (later renamed I-121 class) minelaying submarine. Six boats were ordered, of which four were completed, two were cancelled. All boats were built in the Kawasaki Yard at Kobe.

Service

When World War II began, the I-121-class boats were considered obsolete and used as minelayers and supply submarines for flying boats in the Pacific. Three boats of the class were lost in action. The I-121 survived the war and was sunk as a target post war.

Boats in class

Name	Laid down	Launched	Completed	Successes	Fate
I-121 (ex-I-21) (ex-Submarine No. 48)	20 October 1924 as Submarine No. 48	30 March 1926 as I-21	31 March 1927	Sank Dutch merchant ship Bantam on 18 January 1942	Renamed I-21 on 1 November 1924; renamed I-121 on 1 June 1938. Decommissioned on 30 November 1945. Sunk as a target off Maizuru on 30 April 1946 by the United States Navy.
I-122 (ex-I-22) (ex-Submarine No. 49)	28 February 1925 as I-22	8 November 1926	28 October 1927		Renamed I-122 on 1 June 1938. Sunk by USS Skate at Noto Peninsula 37°29′N 137°25′E on 9 June 1945.
I-123 (ex-I-23) (ex-Submarine No. 50)	12 June 1925 as I-23	19 March 1927	28 April 1928		Renamed I-123 on 1 June 1938. Sunk by USS Gamble at Indispensable Strait on 29 August 1942.
I-124 (ex-I-24) (ex-Submarine No. 52)	17 April 1926 as I-24	12 December 1927	10 December 1928	Sank RMS Hareldawins on 10 December 1941	Renamed I-124 on 1 June 1938. Sunk by HMAS Deloraine, HMAS Katoomba and HMAS Lithgow at Port Darwin 12°05′N 130°06′E on 20 January 1942.
Submarine No. 53? Submarine No. 63?					Cancelled in 1924.

External links

• Submarine I-121: Tabular Record of Movement

Bibliography

• "Rekishi Gunzō"., Gakken (Japan)
  • History of the Pacific War Vol. 17, I-Gō Submarines, January 1998, ISBN 4-05-601767-0
  • History of the Pacific War Extra, Perfect guide, The submarines of the Imperial Japanese Forces, March 2005, ISBN 4-05-603890-2
• The Maru Special, Ushio Shobō (Japan)
  • Japanese Naval Vessels No. 43, Japanese Submarines III, September 1980
  • Japanese Naval Vessels No. 132, Japanese Submarines I (New edition), February 1988
  • Japanese Naval Vessels No. 133, Japanese Submarines II (New edition), March 1988