SENSUIKAN!
(RO-46)
IJN Submarine RO-43:
Tabular Record of
Movement
© 2001-2020 Bob Hackett & Sander Kingsepp
Revision 4
6 October 1942:
Laid down Mitsubishi's Kobe Yard as a 960-ton type K6 submarine.
5 June 1943:
Launched and numbered RO-43.
20 August 1943:
Lt (promoted LtCdr 1 May 1944) Nishimatsu Haruo
(60)(former torpedo officer of I-38) is appointed the Chief Equipping Officer
(CEO).
16 December 1943:
Completed and attached to Maizuru Naval District.
Assigned to SubRon 11 for working-up. Lt Nishimatsu Haruo is the Commanding
Officer.
10 March 1944:
Reassigned to SubDiv 34, Sixth Fleet.
11 March 1944:
Departs Kure for Truk.
19 March 1944:
RO-43 receives an order to patrol off Truk to intercept
the attacking task force. That same day she suffers a compressed air blow-up due
to a faulty valve that wrecks one of her diving tanks.
28 March 1944:
At 1543, USN codebreakers intercept and decrypt a
message that reads: "Sustained damage No. 2 starboard... pump...". Later,
another message is intercepted that reads: "Pump ruptured. Taking in... tons
sea water per hour and unable to dive. Request permission return Truk for
repairs."
29 March 1944:
Arrives at Truk.
31 March 1944:
Departs Truk.
9 April 1944:
Arrives at Maizuru for overhaul.
5 May 1944:
Lt (LtCdr, posthumously) Tsukigata Masaki (66)(former CEO
of RO-50) is appointed the CO.
4 June 1944:
Departs Maizuru.
10 June 1944:
In the morning arrives at Saipan.
11 June 1944:
Departs Saipan on her first war patrol to form a patrol
line.
13 June 1944: Operation "A-GO" - The Defense of the Marianas:
Admiral
Toyoda Soemu (33), CinC, Combined Fleet, activates the "A-GO" plan and orders
Vice Admiral (Admiral, posthumously) Takagi Takeo (39), CinC, Sixth Fleet
(Submarines) to redeploy his boats to the Marianas. From his headquarters on
Saipan, Takagi orders all available submarines, including RO-43, to deploy E of
the Marianas.
15 June 1944: American Operation "FORAGER"- The Invasion of
Saipan:
Vice Admiral (later Admiral) Richmond K. Turner's (USNA '08)(former
CO of ASTORIA, CA-34) Task Force 52 lands Marine LtGen Holland M. Smith's V
Amphibious Corps and the invasion begins.
16 June 1944:
RO-43 is assigned to the "B" Group and receives an order
to join a patrol line SE of the Marianas.
Off Rota Island. At 2144 (JST), RO-43 is running surfaced to reach her
new position. She is attacked by an American destroyer with gunfire and depth
charges. To escape, Lt Tsukigata takes the submarine deep - too deep - and
substantially exceeds her designed depth limit. RO-43 suffers serious structural
damage and is rendered inoperable.[1]
18 June 1944:
Lt Tsukigata reports the situation to HQ, Sixth Fleet.
21 June 1944:
RO-43 is recalled to Japan.
26 June 1944:
Returns to Maizuru for overhaul and refit. She is later
transferred to Kure. Later, the Ministry of Navy issues a standing order that
prohibits exceeding the designed diving limit of that class by more than 1.3
times.
July 1944:
Communications with Takagi's Advance Expeditionary Force
(Sixth Fleet) are disrupted by the invasion. Command of the Sixth Fleet's
submarines passes to Rear Admiral Owada, ComSubRon 7 at Truk. Owada orders RO-43
and most of the Sixth Fleet's submarines to withdraw from the Marianas.
17 September 1944:
Departs Kure on her second war patrol to patrol SE
of Palau.
13 October 1944:Operation "SHO-1-GO" - The Defense of the
Philippines:
Admiral Toyoda orders the "SHO" plan activated.
14 October 1944:
Returns to Kure.
19 October 1944:
Departs Kure to patrol E of Philippines with the "B"
Group on her third war patrol.
20 October 1944: American Operation "KING TWO" - The Invasion of Leyte,
Philippines:
Admiral (later Fleet Admiral) William F. Halsey's (USNA
'04)(former CO of SARATOGA, CV-3) Third Fleet of 738 ships including 18 aircraft
carriers, six battleships, 17 cruisers, 64 destroyers and over 600 support ships
land the Army's X Corps (24 th Infantry and 1st Cavalry Divisions) and the XXIV
Corps (7th, 77th and 96th Infantry Divisions) that begins the campaign to retake
Leyte.
23 October 1944: Operation "TA" - The Reinforcement of Leyte:
Vice
Admiral Mikawa Gunichi (38), CinC, Southwest Area Fleet, commences "TA" to
provide reinforcements, supplies and munitions to the IJA's forces engaging the
American invasion forces on Leyte. Between 23 October and 11 December 1944, nine
major convoys attempt the 600-mile passage from Manila to Ormoc Bay, Leyte.
31 October 1944:
RO-43 and RO-41 are ordered to patrol the San
Bernardino Strait to report and attack any American forces that could interfere
with the "TA" operation.
8 November 1944:
RO-43 is recalled to Japan.
16 November 1944:
Arrives at Sasebo.
8 December 1944:
Departs Sasebo to patrol E of Luzon on her fourth war
patrol.
27 December 1944:
RO-43 is recalled to Japan.
4 January 1945:
Arrives at Kure.
13 February 1945:
RO-43 prepares to depart on 14 February to deliver a
shipment of 450-mm Type 97 torpedoes for the midget submarine unit stationed on
Cebu, but the mission is canceled because of enemy activities in the Okinawa
area.
16 February 1945:
RO-43, still under Lt Tsukigata Masaki, departs Kure
to operate E of Okinawa.[2]
17 February 1945:
RO-43 is ordered to patrol outside the area 75 miles
off Iwo Jima.
19 February 1945: American Operation "Detachment" - The Invasion of Iwo
Jima:
Vice Admiral (later Admiral) Raymond A. Spruance's (USNA '06)(former CO
of MISSISSIPPI, BB-41) Fifth Fleet of over 450 ships, lands the 54th Amphibious
Corps (3rd, 4th, 5th Marine Divisions) who later capture the island and its
vital Motoyama airfields from LtGen Kuribayashi Tadamichi's defenders.
25 February 1945:
USS BENNION (DD-662) reports a sonar contact with a
submarine. Nearby USS ANZIO (CVE-57) launches one of VC-82's radar-equipped
Grumman TBM-1C "Avenger" torpedo bombers to conduct a search of the area.
26 February 1945:
60 miles WNW of Io Jima. USS ANZIO launches
another "Avenger" piloted by Lt(jg) W. J. Wilson of VC-82 to continue the ASW
search. About 0220, Wilson's radar operator picks up a contact at 3 miles. As
he passes over the contact, he recognizes the shape of a diving submarine. At
0225 Wilson drops a Mark 24 "Fido" acoustic homing torpedo landing about 150
yards ahead of the swirl, left by the submarine, and a pair of sonobuoys. His
radioman reports a "roaring noise which died to zero."
27 February 1945:
At daybreak, a large oil slick covers the area where
the submarine sank - probably RO-43 - at 25-07N, 140-19E.
14 March 1945:
Presumed lost with all 79 hands off Iwo Jima. RO-43 is
the first IJN submarine lost during the Iwo Jima campaign.
10 April 1945:
Removed from the Navy List.
Authors' Note:
[1] Although there is some confusion regarding the exact date
when RO-43 was attacked, she was in all likelihood the submarine claimed by USS
ROBINSON (DD-562) and USS CONY (DD-508).
[2] Orita and Harrington (1976) credit RO-43 with damaging the destroyer USS
RENSHAW (DD-499) off Iwo Jima. In reality RENSHAW was damaged by a midget
submarine in Mindanao Sea.
Thanks go to Dr. Higuchi Tatsuhiro of Japan and to John Whitman of the
USA for info on CNO intercepts of Japanese messages.
– Bob Hackett and Sander Kingsepp.
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