Japanese submarine Ro-45

Ro-45 was an Imperial Japanese Navy Kaichū type submarine of the K6 sub-class. Completed and commissioned in January 1944, she served in the central Pacific Ocean during World War II and was sunk in April 1944 during her first combat sortie.

Design and description
The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth. They displaced 1115 LT surfaced and 1447 LT submerged. The submarines were 80.5 m long overall, had a beam of 7 m and a draft of 4.07 m. They had an operational diving depth of 80 m.

For surface running, the boats were powered by two 2100 bhp diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600 hp electric motor. They could reach 19.75 kn on the surface and 8 kn underwater. On the surface, the K6s had a range of 11000 nmi at 12 kn; submerged, they had a range of 45 nmi at 5 kn.

The boats were armed with four internal bow 53.3 cm torpedo tubes and carried a total of ten torpedoes. They were also armed with a single 40-caliber 76.2 mm anti-aircraft (AA) gun and two single 25 mm AA guns.

Construction and commissioning
Ro-45 was laid down as Submarine No. 386 on 20 October 1942 by Mitsubishi at Kobe, Japan. She was launched on 21 July 1943 and was renamed Ro-45 on that day. She was completed and commissioned on 11 January 1944.

Service history
Upon commissioning, Ro-45 was attached to the Maizuru Naval District and assigned to Submarine Squadron 11 for workups. On 14 April 1944, she was reassigned to Submarine Division 34 in the 6th Fleet. She departed Kure, Japan, on 16 April 1944 bound for Truk, which she reached on 27 April 1944.

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. On 30 April 1944, during the second day of strikes, the commander of Submarine Squadron 7 ordered Ro-45 and the submarines JAPANESE SUBMARINE I-16, JAPANESE SUBMARINE I-176, JAPANESE SUBMARINE Ro-44, JAPANESE SUBMARINE Ro-106, JAPANESE SUBMARINE Ro-108, and JAPANESE SUBMARINE Ro-115 to intercept Task Force 58.

Loss
At 06:21 local time on 30 April 1944, the U.S. Navy destroyer USS MacDonough (DD-351) made radar contact on an unidentified vessel on the surface 40 nmi south of Truk. The contact disappeared from radar, indicating a submerging submarine. 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 USS Monterey (CVL-26) providing spotting support, made two depth-charge attacks. The destroyer USS Stephen Potter (DD-538) also joined the attack. The destroyer crews noted several underwater explosions after the last depth charge detonated, marking the end of the submarine, which sank at 6.21667°N, 151.31667°W. Oil and debris later rose to the surface.

No other Japanese submarine made contact with Task Force 58, and the submarine MacDonough and Stephen Potter sank probably was Ro-45. On 20 May 1944, the Imperial Japanese Navy declared her to be presumed lost off Truk with all 74 men on board. She was stricken from the Navy list on 10 July 1944.

Some sources suggest that Ro-45 was sunk off Saipan in the Mariana Islands by the U.S. submarine USS Seahorse (SS-304) on 20 April 1944, but that is incorrect because Ro-45 remained active after that date. Other sources incorrectly identify the Japanese submarine sunk on 30 April 1944 as JAPANESE SUBMARINE I-174, but I-174 was sunk on 12 April 1944.