SENSUIKAN!

© 2001-2017 Bob Hackett & Sander Kingsepp:
Revision 2

5 June 1922:
Kobe. Laid down at Mitsubishi Shipbuilding as a 990-ton L4 submarine.

19 May 1923:
Launched.

13 August 1923:
LtCdr (later Cdr) Ishibashi Toshinari (36) is appointed the Chief Equipping Officer (CEO).

9 February 1924:
Completed and commissioned in the IJN as Submarine No. 72. Attached to Sasebo Naval District. LtCdr Ishibashi is the Commanding Officer.

1 November 1924:
Submarine No. 72 is renumbered RO-61.

1 December 1924:
Assigned to SubDiv 26. LtCdr (later Rear Admiral) Takatsuka Seigo (38)(former CO of RO-23) is appointed the CO.

June 1926:
Participates in underwater habitability tests. Twenty sailors receive poisoning after a dummy torpedo explosion and are treated aboard JINGEI.

1 December 1926:
LtCdr (later Vice Admiral) Oka Takazumi (39)(former acting CO of RO-55) is appointed the CO.

20 May 1927:
LtCdr (Vice Admiral, posthumously) Yatsushiro Sukeyoshi (40)(former CO of RO-60) is appointed the CO.

16 May 1928:
Lt (later Rear Admiral) Imaizumi Yoshijiro (44)(the current CO of RO-60 and RO-62) is appointed the CO of RO-61 as an additional duty.

10 December 1928:
LtCdr (later Rear Admiral) Nishina Kozo (44)(former CO of RO-55) is appointed the CO.

1 November 1929:
Placed in reserve at Sasebo. LtCdr Kamura Karoku (44) (former CO of RO-30) is appointed the CO of RO-61 and RO-62 (until 30 November) as an additional duty.

22 April 1930:
LtCdr (Captain, posthumously) Okushima Takasaburo (44) (former CO of RO-66) is appointed the CO.

3 June 1930:
LtCdr (later Captain) Kijima Moriji (44)(former CO of RO-59) is appointed the CO.

15 November 1930:
LtCdr (later Captain) Takezaki Kaoru (45)(current CO of RO-60) is appointed the CO of RO-61 as an additional duty.

1 December 1930:
LtCdr Fukuda Isamu (44)(former CO of SUMIDA) is appointed the CO.

2 November 1931:
Lt (later Captain) Shimazui Takemi (47)(former CO of RO-66) is appointed the CO.

4 November 1931:
Placed in reserve at Sasebo.

14 November 1931-24 September 1932:
Lt Shimazui (promoted LtCdr 1 December 1931) is appointed the CO of RO-62 as an additional duty.

1 September 1933:
Cdr (later Captain) Hirano Rokuzo (41)() is appointed the CO of RO-61 as an additional duty.

6 September 1933:
Lt (promoted LtCdr 15 November; later Captain) Nishino Kozo (48)(former CO of RO-32) is appointed the CO.

20 March 1934:
Cdr Hirano Rokuzo (41) is appointed the CO (his second tour as the CO of that boat).

16 July 1934:
LtCdr (later Captain) Nanri Katsuji (48)(former CO of RO-28) is appointed the CO.

15 November 1934:
LtCdr (later Captain) Shichiji Tsuneo (49)(the current CO of RO-60) is appointed the CO of RO-61 and RO-62 as an additional duty.

15 December 1934:
Placed in reserve at Sasebo. Mothballed. Lt (later Captain) Tonozuka Kinzo (50)(former CO of RO-56) is appointed the CO of RO-60, RO-61 and RO-62 as an additional duty.

15 November 1935:
LtCdr (Captain, posthumously) Izu Juichi (51)(former navigating officer of I-60) is appointed the CO of RO-60, RO-61 and RO-62 as an additional duty.

15 February-1 December 1936:
Lt (Rear Admiral, posthumously) Togami Ichiro (51) (former torpedo officer of I-60) is appointed the CO of RO-60, RO-61 and RO-62 as an additional duty.

15 December 1938:
Placed in 3rd reserve at Sasebo. LtCdr (Captain, posthumously) Harada Hakue (52)(former torpedo officer of I-7) is appointed the CO of RO-60 and RO-61 as an additional duty.

27 July 1939:
Lt (Cdr, posthumously) Taoka Kiyoshi (55)(former CO of I-66) is appointed the CO of RO-60 (until 1 September) and RO-61 as an additional duty.

5-20 October 1939:
LtCdr (Captain, posthumously) Obika Masaru (53)(the current CO of RO-66) is appointed the CO of RO-61 as an additional duty.

15 November 1939:
Assigned to SubRon 7's SubDiv26, Fourth Fleet.

15 October 1940:
Placed in reserve at Sasebo. LtCdr (Captain, posthumously) Ohashi Katsuo (53)(former CO of RO-67) is appointed the CO of RO-61 and RO-62 (until 30 October 1940) as an additional duty.

31 July 1941:
LtCdr (Cdr, posthumously) Yamamoto Hideo (56)(former torpedo officer of I-3) is appointed the CO.

2 December 1941:
The coded signal "Niitakayama nobore (Climb Mt. Niitaka) 1208" is received from the Combined Fleet. It signifies that hostilities will commence on 8 December (Japan time). Mt. Niitaka, located in Formosa (now Taiwan), is then the highest point in the Japanese Empire.

6 December 1941:
Kwajalein. RO-61 is in Captain Matsuo Yoshiyasu's (47) SubDiv 26 of Rear Admiral Onishi Shinzo's (42)SubRon 7, Fourth Fleet with RO-60 and RO-62. LtCdr Yamamoto Hideo is the CO.

8 December 1941: The First Attack on Wake Island:
Kwajalein. SubDiv 26 is on 'standby alert' at the outbreak of hostilities.

Wake Island is assaulted by Rear Admiral (Vice Admiral, posthumously) Kajioka Sadamichi's (former CO of KISO) Occupation Group: DesRon 6's light cruiser YUBARI, eight destroyers, two transports and RO-65, RO-66 and RO-67. The United States Marines beat back the first assault with their 5-inch shore batteries. Kajioka loses LtCdr Takatsuka Minoru's destroyer HAYATE to the shore batteries and LtCdr Ogawa Yoichiro's destroyer KISARAGI to Marine Grumman F4F "Wildcats".

12 December 1941:
CarDiv 2's HIRYU and SORYU are detached from Vice Admiral (Admiral, posthumously) Nagumo Chuichi's (former CO of YAMASHIRO) Striking Force returning from Pearl Harbor to reinforce Kajioka, as is Rear Admiral (later Vice Admiral) Abe Hiroaki's (former CO of FUSO) CruDiv 8's TONE, CHIKUMA and two destroyers. Rear Admiral (Vice Admiral, posthumously) Goto Aritomo's (former CO of MUTSU) CruDiv 6's AOBA, KINUGASA, KAKO, FURUTAKA, seaplane tender CHIYODA and two other destroyers also reinforce Kajioka. Rear Admiral Abe, now senior officer present, has overall command.

SubDiv 26's RO-60, RO-61 and RO-62 are assigned to the reinforced Wake Occupation Group and sortie from Kwajalein.

23 December 1941: The Second Attack on Wake Island:
After a magnificent stand, Wake's garrison is overwhelmed and its few defenders surrender.

27 December 1941:
RO-61 returns to Kwajalein.

5 January 1942:
Reassigned to Marshalls Area Guard Unit with RO-62. Patrols off Kwajalein.

1 February 1942: American Air Raid on Kwajalein:
Vice Admiral (later Fleet Admiral) William F. Halsey Jr's (USNA ’04) Task Force 8 (USS ENTERPRISE (CV-6) raids Kwajalein and Wotje in the Marshall Islands. Douglas "Dauntless" SBDs of VB-6 and VS-6 and Douglas TBD "Devastators" of VT-6 sink a transport and damage the light cruiser KATORI, flagship of the Sixth Fleet's (Submarines) Commander, Vice Admiral Shimizu Mitsumi (36)(former CO of ISE). I-23, submarine depot ship YASUKUNI MARU and several other important ships are also damaged in the raid.

Two hours after the attack, Sixth Fleet HQ orders SubRon 1's I-9, I-15, I-17, I-19, I-23, I-25 I-26 and RO-61 and RO-62 put to sea to intercept Halsey's force, but they fail to make contact.

9 March 1942:
Arrives at Truk with RO-61.

19 March 1942:
RO-61 and -62 depart Truk for Saipan.

22 March 1942:
Arrive at Saipan, depart on the same day for Sasebo.

30 March 1942:
Arrive at Sasebo.

23 May 1942:
Lt (LtCdr, posthumously) Tokutomi Toshisada (59)(former torpedo officer of I-3) is appointed the CO.

31 May 1942:
Departs Sasebo for Saipan with RO-61.

6 June 1942:
RO-62 and RO-61 arrive at Saipan.

7 June 1942:
Depart Saipan for Truk.

10 June 1942:
Arrive at Truk.

27 June 1942:
Depart Truk for Yokosuka.

5 July 1942:
Arrive at Yokosuka.

14 July 1942:
SubDiv 26 is reassigned to the Fifth Fleet.

24 July 1942:
Departs Yokosuka for Paramushiro in company of RO-61.

30 July 1942:
RO-62 and RO-61 arrive at Paramushiro.

1 August 1942:
Depart Paramushiro for Kiska.

5 August 1942:
Arrive at Kiska.

August 1942:
The RO-61 is based at Kiska, Aleutians in Cdr (later Captain) Kato Ryonosuke's SubDiv 33 with I-6, RO-62, RO-63, RO-64, RO-65, RO-67 and RO-68.

7 August 1942:
Rear Admiral (later Vice Admiral) William W. Smith's (USNA '09)(former Chief of Staff to Admiral H. E. Kimmel (USNA '04)), TG 8.6 shells Kiska. RO-61, RO-64, RO-68 and I-6 anchored in the harbor crash-dive to escape damage. After the bombardment, some of the submarines are sent to intercept the task group, but they fail to overtake the Americans.

8 August 1942:
Depart Kiska to intercept the American TG.

10 August 1942:
Return to Kiska.

11 August 1942:
Departs to patrol off Kiska in anticipation of another raid.

13 August 1942:
Returns to Kiska.

15 August 1942:
Departs to patrol off Kiska.

17 August 1942:
Returns to Kiska.

28 August 1942:
A Kiska-based Aichi E13A1 "Jake" reconnaissance plane detects the 1,766-ton BARNEGAT-class seaplane tender USS CASCO (AVP-12) and a destroyer in Nazan Bay at Atka Island, Aleutians, but mistakenly identifies CASCO as a light cruiser. RO-61, RO-62 and RO-64 sortie to intercept her.

29 August 1942:
All three submarines arrive off Atka. Lt Tokutomi, the CO of the northernmost RO-61 is ordered to penetrate Nazan Bay to lure the Americans out.

30 August 1942:
After sunset, Lt Tokutomi enters Nazan Bay and makes a slow, cautious approach that almost depletes his batteries. From 875 yards, he fires a spread of three 6th Year Type torpedoes at what he identifies as a "NORTHAMPTON"-class heavy cruiser. The first one passes the CASCO and lands on the beach. The third torpedo also misses but the second hits CASCO's forward engine room and damages the tender severely. She is beached to prevent sinking. Lt Tokutomi reports one hit on a NORTHAMPTON-class cruiser. [1]

31 August 1942:
Aleutian Islands. In the lee of the Atoka volcano, Lt S. E. Coleman of VP-42, flying a PBY-5A "Catalina" through the fog, spots a submarine on the surface, probably recharging her batteries. He strafes her and drops two depth charges, heavily damaging the submarine. Lt Carl H. Amme of VP-43, flying another "Catalina", also makes a depth-charge attack. The submarine crash-dives, leaving a large oil slick.

Lt Amme signals to nearby LtCdr H. H. McIllhenny's USS REID (DD-369) and directs her to the site. Amme marks the oil slick with smoke floats. McIllhenny then drops two patterns of 13 depth charges each that damage the submarine and forces her to surface.

RO-61 first runs at 130 feet, but after the first pattern dives to 200 feet. The next attack causes multiple leaks in her diesel and electrical engine rooms. The battery compartment is flooded and the boat fills with chlorine gas. To fight the stern trim, the sailors haul bags with rice and canned foods to the bow sections.

One of the explosions shorts out the central switchboard. Fires break out in the control room and in the shell magazine. A sudden forward trim causes the crew to haul over twenty 3-in shells to aft compartments. One petty officer dies from chlorine poisoning. Lt Tokutomi orders "Battle Surface".

The Japanese attempt to man their deck gun and some fire at REID with Type 38 Arisaka carbines. Most of the crewmen on deck are cut down by 20-mm fire.

McIllhenny finishes off the submarine with his 5-inch/38 cal main armament. The submarine capsizes and sinks by the stern at 52-36N, 173-57W. Lt Tokutomi and 59 crewmen are lost. REID rescues five survivors who identify their submarine as RO-61.

1 September 1942:
Presumed lost in the Aleutians.

20 October 1942:
Removed from the Navy List.

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Author's Notes:
[1] CASCO was the first warship ever attacked by an RO-class submarine.

Thanks go to Dr. Higuchi Tatsuhiro of Japan.

– Bob Hackett and Sander Kingsepp.

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