IJN Submarine RO-43:
Tabular Record of Movement

2001-2017 Bob Hackett & Sander Kingsepp
Revision 3

6 October 1942:
Kobe. Laid down Mitsubishi Shipbuilding as a 960-ton type K6 submarine.

5 May 1943:
Launched and designated RO-43.

16 December 1943:
Completed and attached to the Maizuru Naval District. Assigned to SubRon 11. LtCdr Nishimatsu Haruo is appointed the Commanding Officer.

1 January 1944:
RO-43 is in Rear Admiral Owada Noboru's (44)(former CO of YAMASHIRO) SubRon 11 for work-up.

10 March 1944:
Reassigned to SubDiv 34, Sixth Fleet.

11 March 1944:
Departs 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:
LtCdr Tsukigata Masaki is appointed the next CO.

4 June 1944:
Departs Maizuru.

10 June 1944:
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)(former CO of HYUGA), CINC, Combined Fleet, activates the A-GO plan and orders Vice Admiral (Admiral, posthumously) Takagi Takeo (39)(former CO of MUTSU), 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:
The 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, LtCdr Tsukigata takes the submarine deep -too deep- and substantially exceeds her designed depth limit. RO-43 suffers serious structural damage and is rendered inoperable.

18 June 1944:
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 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.

10 July 1944:
Vice Admiral Miwa Shigeyoshi (former CO of KINU) at Kure assumes command of the Sixth Fleet from Rear Admiral Owada at Truk.

17 September 1944:
Departs Kure on her second war patrol to patrol SE of Palau .

13 October 1944: Operation "SHO-I-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)(former CO of KIRISHIMA), 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, under LtCdr Tsukigata Seiki, departs Kure to operate E of the Okinawa area.

17 February 1945:
RO-43 is ordered to patrol within an 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 Lt Gen Kuribayashi Tadamishi'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 TBF "Avenger" torpedo-bombers to conduct a search of the area.

26 February 1945:
Volcano Islands. USS ANZIO (CVE-57), launches another Avenger piloted by Lt (j.g.) W. J. Wilson of VC-82 to continue the ASW search. About 0220, Wilson's radar operator picks up a contact. As he passes over the contact, he recognizes the shape of a diving submarine. Wilson drops a pair of sonobuoys and then a Mark 24 "Fido" acoustic homing torpedo.

27 February 1945:
At daybreak, a large oil slick covers the area where the submarine sank - probably RO-43 - at 24-07N, 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:
Thanks go to Dr. Higuchi Tatsuhiro of Japan. Thanks also go to John Whitman of the USA for info on CNO intercepts of Japanese messages.

Bob Hackett and Sander Kingsepp.

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