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  RO-109 Japanese Submarine
Ro-100 Class Submarine

525 Tons (surfaced)
60.90m x 6m x 3.51m
4 x torpedo tubes
(8 Type 95 torpedoes)
2 x 25mm AA guns

Ship History
Built by Kawasaki at Kobe. Launched on April 30, 1943. Commissioned and is based in the Sasebo Naval District. Assigned to Commanding Officer LtCdr Uesugi Kazuaki (former torpedo officer of I-19).

Assigned to SubRon 11 for training. On August 14, 1943 departs Sasebo for Rabaul. Enroute assigned to SubRon 7, (Eighth Fleet/Southeast Area Fleet). Arrives at Rabaul on August 24, 1943 then assigned to SubRon 7's SubDiv 51.

First War Patrol
On September 9, 1943 departs Rabaul to patrol south of Guadalcanal. Returns to Rabaul on October 2, 1943. Next, on October 13, 1943 departs Rabaul on a suppy run to Sarmi, arriving the next day, unloads cargo and departs. During October 15-16 assigned to lifeguard duty to pick up downed G4M Betty crew, but fails to locate them. Afterwards, redirected to the Lae area.

On October 19, 1943 the submarine is detected and chased by USS Reid (DD-369) and USS Perkins (DD-377). Perkins drops depth charges on the submarine, but does not damaging it. RO-109 fires a spread of torpedoes at USS Drayton (DD-366), but misses. Escaping, the submarine returns to Rabaul on October 31, 1943.

Second War Patrol
On November 8, 1943, departs Rabaul for her second war patrol to the Bougainville area. Returns November 24 to Rabaul.

3 December 1943:
Departs Rabaul for her third war patrol to the Bougainville area.

9 December 1943:
Returns to Rabaul.

13 December 1943:
Departs Rabaul on her first supply run to Buin, New Guinea.

16 December 1943:
Arrives at Buin, unloads her cargo, then departs.

19 December 1943:
Returns to Rabaul.

23 December 1943:
Departs Rabaul on her second supply run to Buin.

26 December 1943:
Arrives at Buin, unloads her cargo, then departs.

30 December 1943:
Returns to Rabaul.

24 January 1944:
Departs Rabaul on her third supply run to Buin.

28 January 1944:
Arrives at Buin, unloads her cargo, then departs.

31 January 1944:
Returns to Rabaul.

7 February 1944:
Departs Rabaul on her second supply run to Sarmi.

9 February 1944:
Arrives at Sarmi, unloads her cargo, then departs.

11 February 1944:
Returns to Rabaul.

20 February 1944:
Departs Rabaul for Truk via New Hanover Island.

25 February 1944:
Arrives at Truk.

26 February 1944:
Departs Truk for Sasebo.

3 March 1944:
Arrives at Saipan, departs on the same day.

11 March 1944:
Arrives at Sasebo for repairs.

20 March 1944:
Lt Sugamasa Tetsuaki (former CO of RO-68) is appointed the next CO. [1]

13 April 1944:
Departs Sasebo for Saipan.

20 April 1944:
Arrives at Saipan.

22 April 1944:
Departs Saipan to patrol N of New Guinea on her fourth war patrol.

29 April 1944:
Joins patrol unit "B" SE of Meleyon Islet.

8 May 1944:
Returns to Saipan.

16 May 1944:
RO-109 departs Saipan on her fifth war patrol to form a picket line with RO-104, RO-105, RO-106, RO-108, RO-112 and RO-116 to warn of American invasion forces approaching the Palaus.

18 May 1944:
The U. S. Navy intercepts radio traffic that indicates the Japanese have established a new submarine picket "NA line" between Truk and the Admiralty Islands to intercept American carriers. LtCdr Walton B. Pendelton's USS ENGLAND (DE-635) departs from the Solomons with RABY (DE-698) and GEORGE (DE-697) as a hunter-killer group to attack the NA line.

27 May 1944:
The Sixth Fleet decodes American signals that indicate that several submarines of the NA line have been sunk. The Japanese flash a warning message. Lt Sugamasa moves RO-109 to a new position 60 miles NW of his original position.

31 May 1944:
Departs the patrol area.

5 June 1944:
Arrives at Truk.

Sixth War Patrol
On June 12, 1944, departs Truk to patrol in the vicinity of Truk. On June 16, 1944 joins patrol unit "D", patroling until June 22 and returns to Truk on June 28, then departs arriving at Sasebo on July 16 for repair and overhaul.

5 August 1944:
LtCdr Oba Saichi (former CO of RO-105) assumes command. Lt Sugamasa is appointed the next CO of RO-49.

5 September 1944:
Lt Yuchi Jun (former torpedo officer of RO-49) assumes command.

25 September 1944:
Reassigned to the Kure SubRon's SubDiv 33.

14 October 1944:
LtCdr Masuzawa Seiji (former CO of I-158) assumes command. Lt Yuchi is later appointed CO of RO-112.

17 October 1944:
The RO-109 is directly attached to C-in-C, Combined Fleet.

20 October 1944:
RO-109 is reassigned to SubDiv 34, Sixth Fleet.

25 October 1944:
Reassigned to patrol unit "C". Departs Kure for the Lamon Bay area on her seventh war patrol.

3 November 1944:
140 miles NNE of Manila. At 0700 (JST), LtCdr Masuzawa fires a spread of torpedoes at an unknown Allied submarine, but does not score any hits. [2]

10 November 1944:
Departs her patrol area.

19 November 1944:
Arrives at Sasebo for repairs and overhaul.

18 December 1944:
Departs Sasebo on her eighth war patrol for an area E of the Philippines.

23 December 1944:
490 nms E of Cape Eluanbi, Taiwan. At 1420, RO-109’s sonar operator picks up an enemy task force and tracks it for a while, but the submarine fails to reach the firing position.

5 January 1945:
330 nms SE of Cape Eluanbi. RO-109’s sonarman again picks up suspicious noises, this time evidently belonging to an enemy convoy bound for Lingayen Gulf.

On January 12, 1945, returns to Sasebo.

3 February 1945:
Departs Sasebo for an area W of Luzon.

16 February 1945:
60 nms W of Lingayen Gulf. At 1800, LtCdr Masuzawa sights one battleship and two cruisers protected by a screen of destroyers, heading north.

17 February 1945:
LtCdr Masuzawa attacks an enemy task force in the same area but scores no hits.

2 March 1945:
Returns to Kure, later transferred to Sasebo for repairs and overhaul.

17 March 1945:
Lt Nakagawa Hiroshi (former CO of RO-62) assumes command. LtCdr Masuzawa is reassigned as CO of I-44 on which he is KIA in Apr '45.

Tenth War Patrol
On April 2, 1945 the submarine departs Sasebo on her tenth war patrol for an area east of Okinawa. The RO-109 is scheduled to arrive in an area 20 miles S of Okinawa by 20 April, but there are no further contacts after her departure.

Sinking History
On April 25, 1945 returning from escorting a convoy to Guam, RO-109 was detected by USS Horace A. Bass (APD-144) SSW of Okino-Daito Jima off Okinawa. The submarine was sunk by a single accurate depth charge salvo. Presumed lost with all 65 crew aboard. Officially removed from the Navy List on June 10, 1945.

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Last Updated
November 16, 2018


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