The second I-55 was one of three Type C cruiser submarines of the C3 sub-class built for the Imperial Japanese Navy. Commissioned in April 1944, she was lost in July 1944 while taking part in the Marianas campaign during World War II. Design and description The Type C3 submarines were derived from the earlier C2 sub-class although with fewer torpedo tubes, an additional deck gun, and less-powerful engines to extend their range. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of . For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the C3s had a range of at ; submerged, they had a range of at . The boats were armed with six internal bow torpedo tubes and carried a total of 19 torpedoes. They were also armed with two /40 deck guns and one twin mount for Type 96 anti-aircraft guns. Construction and commissioning Ordered under the Additional Naval Armaments Supplement Programme and built at Kure Navy Yard at Kure, Japan, I-55 was laid down on 15 June 1942 with the name Submarine No. 628. On 1 November 1942, she was provisionally attached to the Kure Naval District and numbered I-55; she was the second Japanese submarine of that number, the first having been renumbered I-155 on 20 May 1942. Launched on 20 April 1943, she was completed and commissioned one year later, on 20 April 1944. Service history Upon commissioning, I-55 was based in the Kure Naval District and assigned to Submarine Squadron 11 in the 6th Fleet. In late June 1944, she was selected for conversion to carry Special Naval Weapon No. 8, a version of the Fu-Go balloon bomb that could be launched at sea, the conversion involving the installation of hydrogen and balloon-launching equipment. Meanwhile, however, the Combined Fleet had activated Operation A-Go for the defense of the Mariana Islands on 13 June 1944, and the Marianas campaign had begun with the U.S. invasion of Saipan on 15 June. Before her conversion could begin, I-55 got underway from Kure on 30 June 1944, called at Yokosuka from 1 to 6 July 1944, and then departed for Guam towing an Unpoto gun container,