Ha-201-class submarine

The Ha-201-class submarine (波二百一型潜水艦) were a class of small submarines designed for the Imperial Japanese Navy (IJN). They were first deployed in 1945, but never saw combat. The Ha-201's were designed from the outset to have high underwater speed and were based on the earlier Submarine No.71 prototype. The official designation of the submarine was Sentaka-Shō type submarine (潜高小型潜水艦). The type name was shortened to Suichū Kōsoku Sensuikan Ko-gata (水中高速潜水艦小型).

Design and description
At the end of 1944, the Imperial Japanese Navy decided it needed large numbers of high-speed coastal submarines to defend the Japanese Home Islands against an anticipated Allied invasion (named Operation Downfall by the Allies). To meet this requirement, the Ha-201-class submarines were designed as small, fast submarines incorporating many of the same advanced ideas implemented in the German Type XXI and Type XXIII submarines. They were capable of submerged speeds of almost 14 kn.

The Ha-201 class displaced 320 LT surfaced and 440 LT submerged. The submarines were 53 m long, had a beam of 4.00 m and a draft of 3.44 m. For surface running, the submarines were powered by a single 400 bhp diesel engine that drove one propeller shaft. When submerged the propeller was driven by a 1,250 shp electric motor. They could reach 11.8 kn on the surface and 13.9 kn submerged. On the surface, the Ha-201-class submarines had a range of 3000 nmi at 10 kn; submerged, they had a range of 105 nmi at 2 kn. Their armament consisted of two 533 mm torpedo tubes with four torpedoes and a single mount for a 7.7-millimeter machine gun.

Construction
The Japanese planned to build 79 Ha-201-class submarines (Submarines No. 4911 through 4989) under the Maru Sen Programme, prefabricating large sections of the boats, then completing them on the slipway. This was an ambitious goal considering the U.S. bombing campaign, which disrupted Japanese production, and by the time hostilities ceased on 15 August 1945 the Japanese had laid down only 22 submarines and completed only ten.

Service
None of the submarines made operational patrols. Except for one submarine that was wrecked, the Allies after the war scuttled all the submarines that had been completed as well as all the incomplete ones that had been launched. Those which remained on the building ways at the end of the war were scrapped incomplete.