IJN Submarine RO-56:
Tabular Record of
© 2001-2017 Bob Hackett & Sander Kingsepp
2 December 1943:
Tamano. Laid down at Mitsui Zosensho as a
965-ton type K6
submarine, provisionally numbered RO-75.
5 July 1944:
Launched as RO-56.
15 September 1944:
Lt (LtCdr, posthumously) Nagamatsu Masateru
(67)(former torpedo officer of I-162) is appointed the Chief Equipping Officer
15 November 1944:
Tamano. RO-56 is completed and registered in the
IJN. Attached to Maizuru Naval District. Assigned to SubRon 11 for working-up.
Lt Nagamatsu Masateru is the Commanding Officer.
10 February 1945:
Reassigned to SubDiv 34, Sixth Fleet.
16 March 1945:
Arrives at Saeki.
18 March 1945:
Departs Saeki for her patrol area SW of Kyushu in
company of I-8, RO-41 and RO-49.
22 March 1945:
Lt Nagamatsu reports that RO-56 has arrived at her
assigned patrol station.
26 March 1945: American Operation "ICEBERG" - The Invasion of
New York's 77th Infantry Infantry "Statue of Liberty" Division lands
on the Kerama Islands and by 29 March captures advance bases and anchorages.
1 April 1945:
Vice Admiral (later Admiral) Raymond A. Spruance's (USNA
'06) Fifth Fleet, including more than 40 aircraft carriers, 18 battleships, 200
destroyers and over 1,000 support ships surround Okinawa. LtGen Simon B. Buckner
Jr's Tenth Army (7th, 77th, 96th Infantry, 1st, 6th Marine divisions) makes
amphibious landings and begins the campaign to take the island from LtGen
Ushijima Mitsuru's 32nd Army.
9 April 1945:
45 miles W of Okinawa Island. LtCdr E. G. Sanderson's
USS MONSSEN (DD-798) and Cdr W. S. Maddox's MERTZ (DD-691) are screening a
fast-carrier group. MONSSEN makes a sonar contact at 900 yds. Sanderson then
drops three patterns of 13 depth charges. MERTZ drops another three patterns.
MONSSEN drops a final two patterns that probably destroy the RO-56 at 26-09N,
15 April 1945:
Presumed lost with all 79 hands off Okinawa.
25 May 1945:
Removed from the Navy List.
 Several sources suggest that RO-56 was sunk on 18 April
1945 NE of Wake Island by USS SEA OWL (SS-405), but the target in that case was
I-372 (not sunk in that attack). There were no other IJN subs at Wake at that
Thanks go to Dr. Higuchi Tatsuhiro of Japan.
– Bob Hackett and Sander Kingsepp.
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