Ro-104 was an Imperial Japanese Navy Ro-100-class submarine. Completed and commissioned in February 1943, she served in World War II, operating in the Aleutian Islands campaign, New Guinea campaign, and Solomon Islands campaign before she was sunk in May 1944 during her tenth war patrol.
Design and description
The Ro-100 class was a medium-sized, coastal submarine derived from the preceding Kaichū type. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a double hull and 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 Ro-100s had a range of at ; submerged, they had a range of at .
The boats were armed with four internal bow torpedo tubes and carried a total of eight torpedoes. They were also armed with two single mounts for Type 96 anti-aircraft guns or a single L/40 AA gun.
Construction and commissioning
Ro-104 was laid down as Submarine No. 214 on 19 November 1941 by Kawasaki at Kobe, Japan. She had been renamed Ro-104 by the time she was launched on 11 July 1942. She was completed and commissioned on 25 February 1943.
Service history
February–June 1943
Upon commissioning, Ro-104 was attached to the Kure Naval District and was assigned to the Kure Submarine Squadron for workups. She participated in torpedo practice with the submarines , , and on 26 March 1943. She was reassigned to Submarine Squadron 11 on 1 April 1943 and then to Submarine Squadron 7 on 5 June 1943.
Aleutian Islands campaign
On the day Ro-104 was assigned to Submarine Squadron 7, she was detailed Submarine Squadron 1 for service in the Aleutian Islands, where the Aleutian Islands campaign was in its final stages. The Battle of Attu of 11–30 May 1943 had ended in U.S. forces retaking Attu and annihilating its Japanese garrison, and on 21 May 1943 — even before the battle ended — Japanese Imperial General Headquarters had decided to evacuate the isolated Japanese garrison on Kiska. In operations with Submarine Squadron 1, Ro-104 was to support the evacuation.
Ro-104 departed Kure on 7 June 1943 bound for Paramushiro in the Kurile Islands, which she reached on 13 June 1943. She and the submarine refueled from the auxiliary fleet oiler there on 14 June 1943.
First war patrol
Ro-104 got underway from Paramushiro on 19 June 1943 for her first war patrol, assigned a patrol area off Kiska. She joined Patrol Line A west of Attu on 23 June 1943 and operated in it until 28 June, when she was reassigned to the Northern Patrol Unit. Early on the morning of 29 June 1943 she sighted what her commanding officer identified as a large transport and began to pursue it. While she was on the surface at 06:45, she spotted a torpedo fired at her by a submerged submarine and crash-dived. She resurfaced two hours later and resumed her pursuit of the transport, but ultimately discontinued the chase when she identified it as a neutral Soviet merchant ship. She returned to Paramushiro on 30 June 1943.
Second war patrol
Ro-104 departed Paramushiro on 6 July 1943 to begin her second war patrol, again with orders to join Patrol Line A. Her patrol was uneventful, and it concluded with her return to Paramushiro on 21 July 1943. She departed Paramushiro bound for Yokosuka, Japan, which she reached on 28 July 1943.
New Guinea campaign, August–October 1943
Ro-104 departed Yokosuka on 14 August 1943 bound for Rabaul on New Britain, which she reached on 26 August 1943.
Third war patrol
On 4 September 1943, Allied forces landed at Lae, New Guinea, in Operation Postern. Ro-104 departed Rabaul that day to begin her third war patrol, ordered to attack the landing force. She encountered no Allied ships during her patrol, and she returned to Rabaul on 17 September 1943.
Fourth war patrol
Ro-104 got underway from Rabaul on 23 September 1943 for her fourth war patrol, ordered to join the submarines and in intercepting and attacking United States Navy Task Force 76 in the vicinity of Finschafen on New Guinea′s Huon Peninsula. She again found no targets, and she returned to Rabaul on 30 September 1943.