They were one of the fastest submarine class built during World War II, second only to Walter Type XVII closed-cycle powered submarines. Twenty-three units were ordered from the Kure Naval Arsenal under the 1943 construction program. Due to the deteriorating war situation, only eight boats were laid down, and only three, numbered I-201, I-202 and I-203, were completed before the end of the war. None of them saw operational use.
In 1938 the Imperial Japanese Navy constructed an experimental high-speed submarine for evaluation purposes, which was designated for security purposes. Based on previous experience with high-speed, short-range midget submarines, Number 71 displaced only 230 tons surfaced with a length of 140feet. She could attain a submerged speed of over 21kn, making her the fastest submarine of her day. The results gained from experiments with Number 71 formed the basis for the I-201 class submarines.[2]
By late 1942 it had become apparent to the IJN that conventional submarines were unable to survive the new ASW techniques coming into service, such as radar, HF/DF, sonar, and new depth charge projectors. New submarines were required, with a higher underwater than surface speed, quick-diving capability, quiet underwater running, and a high underwater operational radius.
The IJN General Staff made an official request for high-speed submarines in October 1943 and among the ships planned in 1944 to be constructed in 1945 were 23 "underwater high speed submarines" (Sen taka) temporarily designated "Ships No. 4501 - 4523".
The General Staff's final requirements were stated in Order No. 295 dated 29 October 1943 to the Navy Technical Department. These included an underwater speed of 25kn which was reduced to 20kn for practical reasons. Nevertheless, they were the fastest operational submarines of World War II, outpacing even the German Type XXI.[3]
To meet the requirement for high underwater speed the designers had to:
The I-201 class bore little resemblance to earlier I-boats, which were optimized for long range and high surfaced speed. By contrast, the I-201 emphasized submerged performance. It featured powerful electric motors, streamlined all-welded hulls, and a large capacity battery consisting of 4,192 cells. The maximum underwater speed of 19kn was double that of contemporary American designs. The I-201s, like other Japanese submarines of the period,[5] were also equipped with a crude snorkel, allowing underwater diesel operation while recharging batteries.
I-201 displaced 1,291 tons surfaced and 1,451 tons submerged. It had a test depth of 360feet. Armament consisted of four 53 cm (21 in) torpedo tubes and 10 Type 95 torpedoes. The two 25 mm anti-aircraft guns were housed in retractable mounts to maintain streamlining. The submarine was designed for mass production, with large sections prefabricated in factories and transported to the slip for final assembly.
Two submarines, I-201 and I-203, were seized and inspected by the US Navy at the end of the hostilities. They were part of a group of four captured submarines, including the giant and I-401, which were sailed to Hawaii by US Navy technicians for further inspection.
On 26 March 1946, the US Navy decided to scuttle these captured Japanese submarines to prevent the technology from falling into the hands of the Soviet Union. On 5 April 1946, I-202 was scuttled in Japanese waters. On 21 May 1946, I-203 was torpedoed and sunk by submarine off the Hawaiian Islands. On 23 May 1946, I-201 was torpedoed and sunk by . The Hawaii Undersea Research Laboratory found the wreck of the I-201 near Hawaii using submersible craft in 2009.[6]
| Sub class | Boat # | Boat | Builder | Laid down | Launched | Completed | Decommissioned | Fate |
| I-201 (Pr. S563) | 4501 | [7] | 1 March 1944 | 22 July 1944 | 2 February 1945 | 30 November 1945 | Sunk as a target off the Hawaiian Islands by on 23 May 1946 | |
| 4502 | 1 May 1944 | 2 September 1944 | 12 February 1945 | 30 November 1945 | Scuttled by U.S. Navy off Gotō Islands on 5 April 1946 | |||
| 4503 | 1 June 1944 | 20 September 1944 | 29 May 1945 | 30 November 1945 | Sunk as a target off the Hawaiian Islands by on 21 May 1946 | |||
| 4504 | I-204 | 1 August 1944 | 16 December 1944 | 90% complete, sunk by air raid on 22 June 1945, salvaged and scrapped at Kure February–May 1948 | ||||
| 4505 | I-205 | 4 September 1944 | 15 February 1945 | 80% complete, sunk by air raid on 28 July 1945, salvaged and scrapped at Kure May–August 1948 | ||||
| 4506 | I-206 | 27 October 1944 | 26 March 1945 | 85% complete, construction stopped on 26 March 1945, scrapped at Kure October 1946-January 1947 | ||||
| I-207 (Pr. S56B) | 4507 | I-207 | 27 December 1944 | 20% complete, construction stopped on 17 April 1945, scrapped at Kure April–May 1946 | ||||
| 4508 | I-208 | 17 February 1945 | 5% complete, construction stopped on 17 April 1945, scrapped at Kure April–May 1946 with I-207[8] | |||||
| 4509-4523 | Constructions were not started until the end of the war. |
The I-201 design and technology influenced Japanese Maritime Self Defense Force (1959).
A refurbished I-203 is used by the characters in the film Hell and High Water (1954).