The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth. They displaced 1115LT surfaced and 1447LT submerged. The submarines were 80.5m (264.1feet) long overall, had a beam of 70NaN0 and a draft of 4.07m (13.35feet). They had an operational diving depth of 80m (260feet).[1]
For surface running, the boats were powered by two 21000NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600hp electric motor.[2] They could reach 19.75kn on the surface and underwater. On the surface, the K6s had a range of 11000nmi at ; submerged, they had a range of 45nmi at .
The boats were armed with four internal bow 53.3cm (21inches) torpedo tubes and carried a total of ten torpedoes. They were also armed with a single 40-caliber 76.2abbr=onNaNabbr=on anti-aircraft (AA) gun and two single 250NaN0 AA guns.[3]
Ro-45 was laid down as Submarine No. 386 on 20 October 1942 by Mitsubishi at Kobe, Japan.[4] She was launched on 21 July 1943 and was renamed Ro-45 on that day.[4] She was completed and commissioned on 11 January 1944.[4]
Upon commissioning, Ro-45 was attached to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups.[4] On 14 April 1944, she was reassigned to Submarine Division 34 in the 6th Fleet.[4] She departed Kure, Japan, on 16 April 1944 bound for Truk, which she reached on 27 April 1944.[4]
While Ro-45 was at Truk, the aircraft carriers of United States Navy Task Force 58 began two days of airstrikes against Truk on 29 April 1944.[4] On 30 April 1944, during the second day of strikes, the commander of Submarine Squadron 7 ordered Ro-45 and the submarines,,,,, and to intercept Task Force 58.[4]
At 06:21 local time on 30 April 1944, the U.S. Navy destroyer made radar contact on an unidentified vessel on the surface south of Truk.[4] The contact disappeared from radar, indicating a submerging submarine.[4] MacDonough subsequently gained sonar contact on the submarine and, with an F6F Hellcat fighter from Fighter Squadron 28 (VF-28) aboard the light aircraft carrier providing spotting support, made two depth-charge attacks.[4] [5] The destroyer also joined the attack.[4] The destroyer crews noted several underwater explosions after the last depth charge detonated, marking the end of the submarine, which sank at 6.2167°N 170°W.[4] Oil and debris later rose to the surface.[4]
No other Japanese submarine made contact with Task Force 58, and the submarine MacDonough and Stephen Potter sank probably was Ro-45.[4] On 20 May 1944, the Imperial Japanese Navy declared her to be presumed lost off Truk with all 74 men on board.[4] She was stricken from the Navy list on 10 July 1944.[4]
Some sources suggest that Ro-45 was sunk off Saipan in the Mariana Islands by the U.S. submarine on 20 April 1944, but that is incorrect because Ro-45 remained active after that date.[4] Other sources incorrectly identify the Japanese submarine sunk on 30 April 1944 as,[4] but I-174 was sunk on 12 April 1944.[6]