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 25640NaN0 surfaced and 36440NaN0 submerged. The submarines were 108.7m (356.6feet) long, had a beam of 9.3m (30.5feet) and a draft of 5.1m (16.7feet). They had a diving depth of 100m (300feet).[1]
For surface running, the boats were powered by two 23500NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600hp electric motor. They could reach 17.7kn on the surface and underwater.[2] On the surface, the C3s had a range of 27000nmi at ; submerged, they had a range of 105nmi at .
The boats were armed with six internal bow 53.3cm (21inches) torpedo tubes and carried a total of 19 torpedoes. They were also armed with two 140mm/40 deck guns and one twin mount for 250NaN0 Type 96 anti-aircraft guns.[3]
Ordered under the Additional Naval Armaments Supplement Programme and built at the Kure Naval Arsenal at Kure, Japan, I-55 was laid down on 15 June 1942 with the name Submarine No. 628.[4] On 1 November 1942, she was provisionally attached to the Kure Naval District and numbered I-55;[4] she was the second Japanese submarine of that number, the first having been renumbered I-155 on 20 May 1942.[5] Launched on 20 April 1943,[4] she was completed and commissioned one year later, on 20 April 1944.[4]
Upon commissioning, I-55 was based in the Kure Naval District and assigned to Submarine Squadron 11 in the 6th Fleet.[4] 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.[4] 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.[4] Before her conversion could begin, I-55 got underway from Kure on 30 June 1944,[4] called at Yokosuka from 1 to 6 July 1944,[4] and then departed for Guam towing an Unpoto gun container,[4] a 70adj=onNaNadj=on sled that could carry up to 15 tons of cargo, usually in the form of three Type 96 15cm (06inches) howitzers and ammunition for them.[6]
While she was at sea on 10 July 1944, I-55 was reassigned to Submarine Division 15 in the Advance Force,[4] and on 13 July she received orders to abort her supply mission to Guam and proceed to Tinian to rescue the staff of the 1st Air Fleet there.[4] She cast the Unpoto container adrift[4] and headed for Tinian. At 00:40 Japan Standard Time on 13 July, she transmitted a message to 6th Fleet Headquarters estimating that she would arrive off Tinian on 15 July.[4] The Japanese never heard from her again.
At 21:20 on 13 July 1944, an American patrol plane spotted a Japanese submarine submerging in the Philippine Sea off Saipan′s Rorogattan Point.[4] The submarine′s position was reported to a United States Navy hunter-killer group, which detached the high-speed transport and destroyer escort to hunt it down.[4] The two ships arrived at the submarine′s last reported position at 00:22 on 14 July 1944 and began their search.[4] Seven hours later, William C. Miller picked up a sound contact at a range of 1700yd and approached the contact at . She began her attack at 07:26 by dropping a pattern of 13 depth charges, followed by a second pattern of 13 depth charges at 07:52. At 0804, her crew observed pieces of wood rising to the surface about 500yd ahead on William C. Miller′s starboard bow, then heard a heavy underwater explosion at 08:05 that shook the ship, followed by bubbles rising to the surface that made the water appear to boil.[4] William C. Miller dropped a third pattern of 13 depth charges at 0806, sinking the submarine.[4] An oil slick and debris covered the surface, and William C. Miller steamed into the slick and recovered pieces of cork insulating material, splintered wooden decking, and a seaman's cap at 15.3°N 170°W.[4]
It remains a matter of dispute as to whether William C. Miller sank I-55 or the submarine .[4] The destroyer escorts and also have received credit for sinking I-55 in an antisubmarine action on 28 July 1944.[7] [8]
On 15 July 1944, the Imperial Japanese Navy declared I-55 to be presumed lost with all 112 hands off Tinian.[4] She was stricken from the Navy list on 10 October 1944.[4]