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^?).

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.

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.