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RO-101 Japanese Submarine

IJN
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

Sub History
Built by Kawasaki Yard at Kobe. Completed October 1, 1942 as RO-101. Commissioned in the Imperial Japanese Navy (IJN) under the command of Lt Orita Zenji and assigned to the Kure. On November 1, 1942 Zenji was promoted to the rank of Lt. Commander.

On January 16, 1943 this submarine was assigned to Rear Admiral Harada Kaku's SubRon 7 in SubDiv 13, in Vice Admiral Mikawa Gunichi's Eighth Fleet at Rabaul. Two days later, the submarine departs Yokosuka. On January 25, 1943 arrives Truk.

First War Patrol
On February 4, 1943 departs Truk, and patrols as part of the covering force for Operation KE-GO, the withdrawal from Guadalcanal. Returns to Rabaul on February 8.

Second War Patrol
On February 9, 1943 departs Rabaul with RO-103 on her second patrol east of Port Moresby.

On February 22, 1943 RO-101 navigator, Lt Kondo Shigeshi, sights a 4,000-ton steamer. After examining the target by persicope, Orita determines that it is a "Q" ship - a merchant armed with hidden guns and depth charges. He decides to make a night attack, but the ship speeds away towards Port Moresby and escapes.

25 February 1943:
Departs the patrol area.

28 February 1943:
Returns to Rabaul.

5 March 1943:
The RO-101 departs Rabaul to rescue survivors of Admiral Kimura's troop convoy, lost during the Battle of the Bismarck Sea.

On March 7, 1943 south of Dampier Strait RO-101 rescues survivors from the sinking of Nojima Maru including Captain Matsumoto Kametaro, CO and 44 IJA infantrymen from lifeboats.

8 March 1943:
Returns to Rabaul.

13 March 1943:
The RO-103 is dispatched to rescue survivors of Kimura's convoy.

On March 15, 1943, RO-103 ran aground on an uncharted reef at 08-20S, 150-45E and signaled Rabaul for assistance and RO-101 was ordered to the scene to perform a tow. Meanwhile, RO-103 dumps food, supplies and torpedoes and breaks free from the reef before RO-101 arrives.

On March 19, 1943 RO-110 departs Rabaul for a patrol area southeast of Guadalcanal, but soon after departure most of the crew fall sick with food poisoning and the patrol is aborted.

On March 21, 1943 departs Rabaul on her third war patrol for the Solomons to gather weather data, perform air-sea rescue and attack enemy shipping.

5 April 1943:
The RO-101 is ordered to proceed to Cape Esperance, Guadalcanal and rescue a downed bomber crew, but Orita is held off by American PT-Boats and has to abort the mission.

12 April 1943:
Returns to Rabaul.

30 April 1943:
Departs Rabaul on her fourth war patrol for the Samarai Bight, New Guinea.

21 May 1943:
Arrives at Rabaul.

8 June 1943:
Departs Rabaul to patrol E of Guadalcanal.

17 June 1943:
Redirected to the Gatukai –Munda area.

29 June 1943:
The RO-101 is ordered to return to Rabaul.

30 June 1943:
Submerged off Munda, reports sighting enemy landing craft to ComSubRon 7, Rear Admiral Harada, at Rabaul. The RO-101 is ordered to approach and attack the Munda beachhead from the W of Rendova. Orita attempts to penetrate the PT-Boats ringed around the landing site, but cannot.

2 July 1943:
Orita attempts again to attack the landing beach, but still cannot penetrate the PT-Boat defense. He withdraws to sea to charge his batteries at night, but receives orders to return to Rabaul.

3 July 1943:
Arrives at Rabaul.

8 July 1943:
Departs Rabaul on her sixth war patrol to penetrate the Rice Anchorage, Kula Gulf.

12 July 1943:
The RO-101 is on the surface recharging her batteries. At 1650, the USS TAYLOR (DD-468), escorting a convoy, picks up a contact on her SG radar and closes to 2,500 feet of the RO-101. At 1654, the destroyer's lookouts have a visual ID on the submarine’s conning tower. The TAYLOR illuminates the target with her searchlight and opens fire. The RO-101’s Executive Officer, Lt Tokugawa Hiromi and two lookouts are killed with the first hits. LtCdr Orita has to drag their bodies away before he can descend into the conning tower and close the upper hatch, so that the submarine can finally dive. The RO-101 dives to 460 feet. Orita orders the main tanks blown in an attempt to stop the sinking.

At 1710, the TAYLOR drops two more depth-charges that render periscope No. 1 inoperable. The RO-101 remains submerged for the next two hours. The temperature aboard rises to +104 F (+40 C). Towards evening, the RO-101 surfaces and proceeds to the NW coast of Kolombangara Island for makeshift repairs.

Inspection of the boat indicates numerous dents in the hull and that the periscope must be replaced. After the sunset her crew heard heavy gunfire and saw searchlight beams (the Battle of Kolombangara). The RO-101 is ordered to rescue the survivors from the JINTSU, but can not execute it.

During the afternoon of July 13, 1944, while charging her batteries on the surface west of Shortland, RO-101 is attacked by a patrol plane forcing Orita to crash-dive. The plane drops two bombs, but misses but her second periscope is damaged and inoperable.

14 July 1943:
Returns to Rabaul. Repairs last three weeks

7 August 1943:
Departs Rabaul on her seventh war patrol for the Kolombangara area.

18 August 1943: The Battle off Horaniu:
Rear Admiral (Vice Admiral, posthumously), the Baron, Ijuin Matsuji (former CO of KONGO) leads the SAZANAMI (F), HAMAKAZE, ISONAMI and the SHIGURE screening 13 Diahatsu barges and three motor torpedo boats. They are carrying IJA and SNLF troops from Buin to Horaniu on Vella Lavella.

Captain Thomas Ryan is dispatched to intercept the Japanese with the NICHOLAS (DD-449), O'BANNON (DD-450), CHEVALIER (DD-451) and the TAYLOR (DD-468). At 0040, a Japanese scout plane drops flares and illuminates the American destroyers 15,000 yards W of the convoy. Between 0046 and 0055, Ijuin's destroyers launch 31 torpedoes at the Americans, but Ryan turns into them and they all miss. Both sides open fire, but the range is long and the gunfire is ineffective. The convoy scatters. Admiral Ijuin withdraws to the NW. Ryan sinks two small subchasers, but the barges later rescue 9,000 Japanese troops from Kolombangara.

About 0100, in the RO-101, LtCdr Orita spots gunfire flashes to the north through his periscope. At 0200, his sound operator picks up destroyer screws coming down the "Slot". Orita quickly sets up and at a range of only 600 yards fires four torpedoes at the second destroyer, but they all pass astern! The destroyer is making 30 knots, much faster than Orita calculated.

20 August 1943:
The RO-101 is reassigned to SubDiv 51 with the RO-100. Lt Arima Fumio (former torpedo officer of I-175) is notified of his selection as the next Commanding Officer of the RO-101.

26 August 1943:
The RO-101 returns to Rabaul. LtCdr Orita receives a signal that he is being reassigned.

28 August 1943:
Bougainville. A Kawanishi H6K "Mavis" is shot down by Lt Charles J. Alley's PB4Y-1 "Liberator" of the VB-104's "Buccaneers" based at Guadalcanal. The Mavis was transporting several passengers from Truk to Rabaul including the prospective CO of the RO-101 Lt Arima who is KIA.

1 September 1943:
Lt Fujisawa Masakata is selected as the next Commanding Officer of the RO-101.

4 September 1943:
Lt Fujisawa assumes command. LtCdr Orita is reassigned as the Commanding Officer of the I-177.

Eighth War Patrol
On September 10, 1943, departs Simpson Harbor off Rabaul on her eighth war patrol to the area southeast of San Cristobal in the Solomon Islands.

Sinking History
On September 15 , 1943 at the south entrance to Indispensable Strait, RO-101 attacks a convoy of two cargo ships escorted by two destroyers bound for Espiritu Santo. At 10:11am, the convoy's escorts: USS Montgomery (DD–121) and USS Saufley (DD-465) spot a torpedo wake and begin searching for the submarine.

Immediately, USS Saufley (DD-465) begins to search down the track of the torpedo's wake. At 12:51pm, she makes sonar contact at 3,000 yards. Over the next three and a half hours, the destroyers makes five depth charge attacks.

At 2:43pm, the submarine surfaces and USS Saufley (DD-465) opens fire on the conning tower with her 5" guns and machine guns. Overhead, PBY-5 Catalina piloted by Lt W. J. Geritz from VP-23 joins the attack and drops two depth charges. The first charge misses, but the second hits.

At 2:46pm the submarine disappears and shortly afterwards, the destroyer crew hears a heavy underwater explosion. By 5:35om, a diesel oil slick covers a square mile of the ocean at roughly Lat 10° 57' S, Long 163° 56' E.

On October 11, 1943, the submarine was presumed lost with all 50 hands in the Solomons. On December 1, 1943 officially removed from the Japanese Navy list.

References
Combined Fleet - IJN Submarine RO-101: Tabular Record of Movement

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Last Updated
November 27, 2022

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