(Kaichu type submarine scanned from "Submarines
of the Imperial Japanese Navy" by Polmar and Carpenter)
IJN Submarine RO-56:
Tabular Record of
© 2001-2013 Bob Hackett & Sander Kingsepp
5 July 1944:
2 December 1943:
Tamano. Laid down at Mitsui Zosensho as a 960-ton type K6 submarine, provisionally numbered RO-57.
Launched and designated RO-56.
15 November 1944:
Tamano. RO-56 is completed and registered in the IJN. Attached to Maizuru Naval District. Assigned to SubRon 11 that same day. Lt Nagamatsu Masateru (67)(former navigating officer of I-153) is the Commanding Officer.
1 January 1945:
RO-56 is in SubRon 11, Sixth Fleet for training and work-up.
10 February 1945:
Reassigned to SubDiv 34, Sixth Fleet.
18 March 1945:
Departs Saeki for her patrol area was SW of Kyushu with RO-49.
26 March 1945: American Operation "ICEBERG" - The Invasion of Okinawa:
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 Mitsuro's 32nd Army.
9 April 1945:
Okinodaito-Jima, S Ryukyus. 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 yards. Sanderson then drops three patterns of 13 depth charges. MERTZ drops another three patterns. MONSSEN drops a final two patterns that probably kill the RO-56 at 26-09N, 130-21E. 
15 April 1945:
Presumed lost with all 79 hands off Okinawa.
25 May 1945:
Removed from the Navy List.
 Some sources claim 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 that was not sunk in that attack. I-372's CO saw one of the American torpedoes slam into the pier next to his sub. There were no other IJN subs at Wake at that time.
Thanks go to Dr. Higuchi Tatsuhiro of Japan and also to Matt Jones for additional CO info.
– Bob Hackett and Sander Kingsepp.
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