Japanese submarine I-400

	I-400 (right) with the U.S. Navy submarine tender USS Proteus (AS-19) (left) and Japanese submarine I-14 (center) in port in Japan in 1945 after the end of World War II.
History
Japan
Name	I-400
Builder	Kure Naval Arsenal, Kure, Japan
Laid down	18 January 1943
Launched	18 January 1944
Completed	30 December 1944
Commissioned	30 December 1944
Stricken	15 September 1945
Fate	Surrendered 27 August 1945; Sunk as target 4 June 1946;
General characteristics
Class & type	I-400-class submarine
Displacement	5,223 long tons (5,307 t) surfaced; 6,560 long tons (6,665 t) submerged;
Length	122 m (400 ft)
Beam	12 m (39 ft)
Draft	7 m (23 ft)
Propulsion	Diesel-electric; 4 diesel engines, 7,700 hp (5,700 kW); Electric motors, 2,400 hp (1,800 kW);
Speed	18.75 knots (21.58 mph; 34.73 km/h) surfaced; 6.5 kn (7.5 mph; 12.0 km/h) submerged;
Range	37,500 nmi (69,400 km) at 14 kn (16 mph; 26 km/h)
Test depth	100 m (330 ft)
Complement	144
Armament	8 × 533 mm (21 in) forward torpedo tubes; 20 × Type 95 torpedoes; 1 × 14 cm/40 11th Year Type naval gun; 3 × 25 mm (1.0 in) 3-barrel machine gun; 1 × Type 96 25 mm (0.98 in) machine gun;
Aircraft carried	3 × Aichi M6A1 Seiran sea-planes

I-400 (伊号第四百潜水艦, I-gō-dai yon-hyaku-sensuikan) was an Imperial Japanese Navy Sentoku-type (or I-400-class) submarine commissioned in 1944 for service in World War II. Capable of carrying three two-seat Aichi M6A1 "Seiran" (Mountain Haze) float-equipped torpedo bombers, the Sentoku-class submarines were built to launch a surprise air strike against the Panama Canal. Until 1965, the Sentaku-type submarines—I-400 and her sister ships I-401 and I-402 —were the largest submarines ever commissioned.

History
I-400 (right) with the U.S. Navy submarine tender USS Proteus (AS-19) (left) and Japanese submarine I-14 (center) in port in Japan in 1945 after the end of World War II.
Japan
Name	I-400
Builder	Kure Naval Arsenal, Kure, Japan
Laid down	18 January 1943
Launched	18 January 1944
Completed	30 December 1944
Commissioned	30 December 1944
Stricken	15 September 1945
Fate	Surrendered 27 August 1945 Sunk as target 4 June 1946
General characteristics
Class & type	I-400-class submarine
Displacement	5,223 long tons (5,307 t) surfaced 6,560 long tons (6,665 t) submerged
Length	122 m (400 ft)
Beam	12 m (39 ft)
Draft	7 m (23 ft)
Propulsion	Diesel-electric 4 diesel engines, 7,700 hp (5,700 kW) Electric motors, 2,400 hp (1,800 kW)
Speed	18.75 knots (21.58 mph; 34.73 km/h) surfaced 6.5 kn (7.5 mph; 12.0 km/h) submerged
Range	37,500 nmi (69,400 km) at 14 kn (16 mph; 26 km/h)
Test depth	100 m (330 ft)
Complement	144
Armament	8 × 533 mm (21 in) forward torpedo tubes 20 × Type 95 torpedoes 1 × 14 cm/40 11th Year Type naval gun 3 × 25 mm (1.0 in) 3-barrel machine gun 1 × Type 96 25 mm (0.98 in) machine gun
Aircraft carried	3 × Aichi M6A1 Seiran sea-planes