Japanese submarine I-201 sunk by a single torpedo from USS Queenfish (SS-393) on May 23rd 1946

The I-201-class submarines were of advanced design built for high underwater speed for the Imperial Japanese Navy during World War II. They were one of the fastest submarine class built during the conflict, 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.

Ordered as Submarine No. 4501, I-201 was laid down on March 1st 1944 by the Kure Naval Arsenal at Kure, Japan. She was launched on July 22nd 1944, and was completed and commissioned on February 2nd 1945 as the lead unit of the I-201 class. The war ended before she could see service and she would eventually arrive at Pearl Harbor on February 13th 1946 with her sister submarine I-203, where her design was studied by the US Navy.

With postwar relations with the Soviet Union deteriorating rapidly and concerns growing in the United States that under postwar agreements the Soviets would demand access to the captured Japanese submarines that would provide the Soviet Navy with valuable information about advanced Japanese submarine designs, the US Navy issued orders on March 26th 1946 to sink all captured Japanese submarines. Accordingly, the U.S. Navy sank I-201 as a target in tests of the Mark 9 exploder off Pearl Harbor on May 23rd 1946. She sank at 10:58 at 21°13′N 158°08′W after the submarine USS Queenfish (SS-393) hit her with a single Mark 18 Mod 2 torpedo.