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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

IJN c1943
Sub History
Built by Kawasaki at Kobe. Laid down April 20, 1942 as RO-100 class submarine. Launched on April 30, 1943. Commissioned into the Imperial Japanese Navy (IJN) as RO-109 in the Sasebo Naval District. On the conning tower was ロ109 [RO-109] with the Japanese flag. Assigned to Commanding Officer LtCdr Uesugi Kazuaki (former torpedo officer of I-19) and assigned to SubRon 11 for training.

Wartime History
On August 14, 1943 departs Sasebo bound for Rabaul and enroute assigned to SubRon 7, (Eighth Fleet/Southeast Area Fleet). On August 24, 1943 arrives at Rabaul and assigned to SubDiv 51.

First War Patrol
On September 9, 1943 departs Rabaul starting her first war patrol and processed to the south of Guadalcanal and on October 2, 1943 returns Rabaul. Next, on October 13, 1943 departs Rabaul on her first supply run to Sio, arriving the next day, unloads cargo and departs. During October 15-16 assigned to lifeguard duty to pick up downed G4M1 Betty is unable 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 releases depth charges but does not damage the submarine. RO-109 fires a spread of torpedoes at USS Drayton (DD-366) but misses and escapes. On October 31, 1943 returns to Rabaul.

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

Third War Patrol
On December 3, 1943 departs Rabaul for her third war patrol to the Bougainville area. On December 9, 1943 returns to Rabaul ending the patrol. Afterwards, the submarine is tasked for emergency supply runs to forward bases to deliver critical supplies to Bougainville and New Guinea.

On December 13, 1943 departs Rabaul on her first supply run mission to Buin. On December 16, 1943 arrives Buin and successfully unloads her cargo then departs. On December 19, 1943 returns Rabaul.

On December 23, 1943 departs Rabaul on her second supply run to Buin. On December 26, 1943 arrives Buin and successfully unloads her cargo then departs. On December 30, 1943 returns Rabaul.

On January 24, 1944 departs Rabaul on her third supply run to Buin. On January 28, 1944 arrives Buin and successfully unloads her cargo then departs. On January 31, 1944 returns Rabaul.

On February 7, 1944 departs Rabaul on her second supply run to Sio. On February 9, 1944 unloads cargo at Sio unloads and departs, two days later returns Rabaul.

On February 20, 1944 departs Rabaul via New Hanover Island and five days later arrives Truk. On February 26, 1944 departs Truk. On March 3, 1944 arrives Saipan and departs the same day. On March 11, 1944 arrives Sasebo for repairs. On March 20, 1944 assigned to Lt. Sugamasa Tetsuaki.

Fourth War Patrol
On April 13, 1944 departs Sasebo and seven days later arrives Saipan. On April 22 1944 departs Saipan starting her fourth war patrol off northern New Guinea. On April 29, 1944 joins patrol unit "B" southeast of Meleyon Islet in Woleai Atoll. On May 8, 1944 the patrol ends when the submarine returns Saipan.

Fifth War Patrol
On May 16, 1944 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 any U. S. invasion forces approaching Palau. By May 18, 1944 the U. S. Navy (USN) intercepts radio traffic to confirm the Japanese submarines have established a submarine picket line between Truk and and the Admiralty Islands and a three destroyer hunter-killer group is deployed to attack the line including USS England (DE-635), USS Raby (DE-698) and USS George (DE-697). On May 27, 1944 RO-109 moves 60 miles northwest of his original position. On May 31, 1944 departs the patrol area and on June 5, 1944 arrives 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", paroling until June 22 and returns to Truk on June 28, 1944 departs arriving at Sasebo on July 16, 1944 for repair and overhaul.

On August 5, 1944 to LtCdr Oba Saichi assumes command. On September 5, 1944 assigned to Lt Yuchi Jun assumes command and at the end of the month assigned to SubDiv 33 at Kure. On October 14, 1944 LtCdr Masuzawa Seiji assumes command and two days later is attached to the Combined Fleet. On October 20, 1944 assigned to Sixth Fleet, SubDiv 34.

On October 25, 1944 departs Kure starting her seventh war patrol and proceeds southward to patrol unit "C" in the Lamon Bay area. On November 3, 1944 while surfaced off Luzon spots an unknown Allied submarine and approaches but the target crash dives before an attack could be made. On November 10, 1944 departs the patrol area and nine days later returns to Sasebo for repairs and overhaul.

Eight War Patrol
On December 18, 1944 departs Sasebo on her eighth war patrol of the area to the east of the Philippines. On December 23, 1944 roughly 490 nautical miles off Cape Eluanbi on Formosa (Taiwan), her sonar tracks targets but is unable reach a firing position. On January 5, 1945 roughly 330 nautical miles southeast of Cape Eluanbi on Formosa (Taiwan) picks up sonar targets, likely the U. S. force bound for Lingayen Gulf on Luzon. On January 12, 1945 returns to Sasebo ending the patrol.

Ninth War Patrol
On February 3, 1945 departs Sasebo to patrol an area west of Luzon. On February 16, 1945 at 6:00pm roughly 70 nautical miles west of Lingayen Gulf on Luzon spots a battleship, two cruisers and destroyer screen headed north and tracks the force. On February 17, 1945 the sub makes an attack but scores no hits. On March 2, 1945 returns to Kure ending the patrol and undergoes repairs and overhaul. On March 17, 1945 Lt Nakagawa Hiroshi assumes command.

Tenth War Patrol
On April 12, 1945 departs Sasebo starting her tenth war patrol via Tsushima Strait departing on April 13, 1945 at 10:00am makes her last transmission then proceeds southward bound for southern Okinawa.

Sinking History
On April 25, 1945 south-southwest of Okino-Daito Jima off Okinawa detected by USS Horace A. Bass (APD-144) south and released a salvo of depth charges that sink the submarine. Afterwards, no transmissions were acknowledged by the submarine. On May 7, 1945 presumed lost with the entire crew of 65. On June 10, 1945 officially removed from the Navy List.

IJN Submarine RO-109: Tabular Record of Movement

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Last Updated
April 25, 2020


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