SENSUIKAN!

2 November 1943:
75 North American B-25 "Mitchell" medium-bombers of the Fifth Air Force’s 3rd, 38th and 345th Bomb Groups, escorted by 70 Lockheed P-38 "Lightnings", attack Rabaul’s airfields and harbor. Three destroyers and eight merchant vessels are sunk or damaged. HOKUYO MARU is damaged in the low level air attacks, but the tow had been slipped and the tokugata unkato midget supply submarine is probably berthed in the inner portion of Simpson Harbor. [6]

USAAF Raid on Rabaul (Naval Historical Center)

3 November 1943:
Convoy 3101 departs Tateyama via Truk for Rabaul. The future CO of the Rabaul midget submarine detachment, Lt Kado Yoshimi (former CO of midget HA-22), with two midget submarine pilots and four technical personnel depart on an unidentified ship and arrive safely later in November.

5 November 1943:
Arrives at Chichi-Jima, Bonins. Destroyer ASANAGI is relieved by destroyer IKAZUICHI.

10 November 1943:
At 1000, auxiliary minesweeper Wa-6 joins the convoy at 10-46N 150-47E.

12 November 1943:
200 km NE of Truk, Carolines. At about 2200, MUKO MARU is torpedoed by LtCdr Harry Hull's (UNNA '32) USS THRESHER (SS-200). At 2218, she sinks at 09-02N, 152-46E. Thereafter, the convoy is split into two echelons.

13 November 1943:
At 1205, the first echelon consisting of HIDAKA, TAIKOKU MARUs and NANKAI MARU No. 2 escorted by destroyer IKAZUCHI, arrives Truk.

14 November 1943:
At 0800, the second echelon consisting of HAGURO, KONEI and SHIBAZONO escorted by destroyer INAZUMA and auxiliary gunboat CHOAN MARU arrives Truk.

17 November 1943:
Truk. At 0700, YAMAZURU MARU, towing a tokugata unkato midget supply submarine, departs Saeki for Palau in convoy No. 708 consisting of ALASKA, KAYO, KIBI, PACIFIC and TAIEI, TAIKO and TOYOKAWA MARUs escorted by patrol boat No. 31 and auxiliary subchasers AOI MARU and TOKUHO MARU No. 10. [1][2]

19 November 1943:
Convoy SO-(unknown) departs Palau consisting of TASMANIA, HOZUGAWA, KENZAN and RYUKO MARUs escorted by submarine chasers CH-37 and CH-38. RYUKO MARU is towing a midget supply submarine. During the voyage south the convoy is plagued by submarine attacks.

25 November 1943:
At 1025, KENZAN MARU is torpedoed and sunk by LtCdr Oscar Hagberg's (USNA ’31) USS ALBACORE (SS-218) at 00-51N, 146-00E. Seven crewmen are KIA.

26 November 1943:
At 1338, YAMAZURU MARU, her midget supply submarine and convoy No.708 arrive at Palau.

28 November 1943:
RYUKO MARU, her midget supply submarine and convoy SO-(unknown) arrive at Rabaul.

10 December 1943:
Truk. At 1230, convoy No. 1103 departs Truk for Rabaul consisting of HIDAKA (5486 grt) and KIMISHIMA MARUs and SHINSEI MARU No. 18 escorted by minesweepers W-21, W-22 and auxiliary submarine-chaser CHa-48. HIDAKA MARU is towing Lt (j.g.) Nagura Tsukasa's (70) midget submarine HA-53 and KIMISHIMA MARU is towing an unkato cargo carrying submersible. Distant cover is provided by old destroyer TACHIKAZE. [1] [2]

15 December 1943:
At 0810, SHINSEI MARU No. 18 that suffered navigational troubles a few days earlier leaves the convoy with W-22 and CHa-48 and heads for Kavieng, New Ireland. At 1210, the same day, the rest of the convoy is attacked by American aircraft, but incurs no damage.

16 December, 1943:
At 1336, the remainder of convoy No. 1103, including the midget submarine and the tokugata unkato midget supply submarine, arrive at Rabaul.

Early January 1944:
Tokuyama, Western Inland Sea. YAMAZURU MARU loads aviation fuel at the depot for delivery to Rabaul. She also carries ammunition and tows Lt (j.g.) Otomo Hiroshi's (70) midget submarine HA-50. [1]

2 January 1944:
Transport NEIKAI MARU departs Kure towing midget submarine Lt (j.g.) Mashima Shiro's HA-49, the first of the Rabaul Detachment's midget submarines.

7 January 1944:
At 0600, NEIKAI MARU departs Saeki for Palau towing HA-49 in convoy No. O-007 with TOKO, KOFUKU, MANSHU and KENNICHI MARUs escorted by destroyer SHIRANUHI, torpedo boat HATO and auxiliary minesweepers TAMA MARU No. 7 and TAKUNAN MARU No. 3. [3]

11 January 1944:
Convoy O-105 departs Saeki for Rabaul via Palau consisting of YAMATSURU, TARUSHIMA, ERIE, DENMARK and NARITA MARUs escorted by minesweeper W-18 and auxiliary minesweeper TAMA MARU. YAMAZURU and TARUSHIMA MARUs is towing Lt (j.g.) Sato Masayoshi 's (70) midget submarine HA-51. In addition, YAMAZURU MARU is towing midget submarine HA-50 and carries the submarines' crews and technical personnel.

About 1230, ERIE MARU is torpedoed in hold No. 2 by LtCdr Charleton L. Murphy’s (USNA ’32) old USS STURGEON (SS-187) at 32-31N, 132-34E. At 1417, ERIE MARU lists over and sinks. 200 of about 2500 soldiers of two Infantry Battalions, a tank unit and a AA unit are KIA.The escorts counter-attack and drop 51 depth-charges. STURGEON incurs slight damage, but escapes. The convoy returns to port.

13 January 1944:
Saeki. At 0200, the convoy again sets out for Palau.

14 January 1944:
155 miles SE of Tanega-Jima. At 2025, YAMAZURU MARU is attacked by LtCdr (later Cdr) Royce L. Gross’ (USNA ’30) USS SEAWOLF (SS-197) at 28-25N, 133-30E. The oiler, that has just discontinued zigzagging, is hit by a torpedo in her No. 2 hold. There is a heavy explosion followed by great fires. YAMAZURU MARU’s cargo of aviation fuel catches fire and begins to cascade into the sea. Another torpedo strikes her between the engine room and No. 3 hold. YAMAZURU MARU lists to port and sinks within a few minutes taking down the midget submarine. 30 crewmen, two gunners and four passengers are KIA.

January 1944:
TAMA MARU is detached at 28N; distant cover is provided by minelater NUWAJIMA.

16 January 1944:
At 1430, convoy No. O-707 and NEIKAI MARU arrive safely at Palau.

Philippine Sea. At 1806, that same day, LtCdr (later Cdr) Albert C. ("Acey') Burrow's (USNA ’28) USS WHALE (SS-239) torpedoes and sinks DENMARK MARU. 1,633 soldiers of the 14th Infantry Division, 31 crewmen, and 20 gunners are KIA. At 2250, LtCdr Gross’ SEAWOLF damages TARUSHIMA MARU by gunfire at 23-00N, 135-00E.

17 January 1944:
LtCdr Burrow's WHALE torpedoes and finishes off damaged TARUSHIMA MARU at 22-50N, 135-40E. She sinks with her midget in tow. 613 troops and 20 crewmen are KIA.

USS WHALE (U.S. Navy)

19 January 1944:
NEIKAI MARU departs Palau for Rabaul in convoy SO-903 with NIPPONKAI MARU and TAKATORI MARU No. 2 escorted by subchasers CH-17 and CH-18.

25 January 1944:
At 1800, convoy O-510 departs Saeki for Palau consisting of HASSHU, HINODE, KIBI, KIZUGAWA, MACASSAR, MITO, YAKUMO, SANKO, TASMANIA and YAKUMO MARUS and SHINTO MARU No. 1 escorted by destroyer HARUKAZE, minesweeper W-17 and auxiliary minesweeper TAMA MARU No.7, the latter as far as 28N. KIZUGAWA MARU is towing HA-52.

26/27 January 1944:
Convoy SO-903 is scheduled to arrive at Rabaul, but is delayed.

Simpson Harbor, Rabaul (U.S. Air Force)

28 January 1944:
110 km WNW of Cape Lambert, New Britain. 13th Air Force B-24 “Liberator” heavy bombers and USN PBY “Catalina” patrol planes bomb NEIKAI MARU. She sinks 75 miles S of Queen Charlotte Island, Bismarcks at 03-45S, 150-38E and takes down midget submarine HA-49. Lt (j.g.) Mashima Shiro is rescued and landed at Rabaul.

6 February 1944: Convoy O-510 arrives safely at Palau. At Palau, towage of HA-52 is taken over by auxiliary collier- tanker SANKO MARU (5,461 grt) from KIZUGAWA MARU.

12 February 1944:
Convoy SO-903 departs Palau for Rabaul consisting of SANKO MARU towing HA-52 and TATSUKIKU MARUs and SHINTO MARU No. 1 escorted by subchasers CH-22 and CH-39 and auxiliary subchaser Cha-16. Near Mussau Island, SANKO MARU and CH-39 are detached for Kavieng, New Hanover/ New Ireland.

16 February 1944:
Off Three Island Harbor, New Hanover. Convoy SO-903 is attacked by nine Fifth Air Force B-25 "Mitchell" medium-bombers of the 500th 'Rough Raiders' Bomb Squadron of the 345 Bomb Group that bomb, strafe and sink SANKO MARU. CH-39 is run aground on a nearby reef. The strafers also damage Lt Nishi Hitoshi's (70) midget submarine HA-52. [4]

That same afternoon, B-25s of the 499th 'Bats Outta Hell' Bomb Squadron of the 345 Bomb Group arrive at the scene and find CH-39 sunk by the stern on a reef and abandoned. The 499th Bomb Squadron finishes her off with thirteen bombs that explode her magazine and boiler and reduce CH-39 to a shattered hulk. They also bomb and strafe a midget submarine on the surface and claim a sinking. [4]

17 February 1944:
B-25s of the 500th Bomb Squadron return to the scene again and find the other midget submarine on the surface. They bomb and strafe the midget submarine and claim a sinking. [5][6]

Type C Midget Submarine under attack off New Hanover, Bismarcks (Scanned from L. Hickey's "Warpath Across the Pacific")

28 October 2011:
Rabaul, Papua New Guinea. Australian minehunter HMAS GASCOYNE, taking part with New Zealand warships in Operation RENDER SAFE explosive ordnance disposal (EOD) in Rabaul from 18 Oct to 4 Nov '11, takes images of the wreck of a submarine 55 meters below the surface in Simpson Harbor. The 20-metre (66-feet) long submarine is partially buried in the harbor floor but remains upright. [7]

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Authors' Notes:
[1] HA-53, the last Type A midget submarine, was completed as the Type B prototype. Later, HA-49 through HA-52 were rebuilt as B Types. All five were sent to Rabaul, towed by merchants, but HA-49 and others were lost in transit. The 46-ton midgets were towed because they were too heavy to be handled by the ships' derricks. HA-53 was the first and only midget sub to arrive safely at Rabaul.

[2] A Tokugata Unkato, also called a "pipe", was a partially completed Type A midget submarine converted into an underwater special cargo carrier. Two sections of a Type A were used together with a torpedo engine and a nose cap. It is doubtful whether any completed Type A's were used for this purpose. Type A Tokugata Unkato "pipe" at Rabaul, postwar

[3] The code name "Ko-Hyoteki' means A-Target. Until late in the war, many Japanese thought the midgets were just that, target ships.

[4] There was only one midget sub involved - HA-52. Some sources say the midget had just been taken off a mother submarine. It was to be provisioned, then put back on the mother sub to be deployed. Postwar, divers find the midget's two counter-rotating props still tied together and the sub's tie-down tackle still attached. Lt (j.g.) Nishi is picked up by CH-39 which itself is soon heavily strafed, bombed and run aground on a nearby reef. Lt (j.g.) Nishi also survives CH-39's ordeal and succeeds in reaching shore by swimming. Thereafter, he travels over land and later by sea and finally arrives Rabaul on 2 March 1944. Later promoted to full Lieutenant he serves as a butai leader in the 86th Guard Unit at the end of the war.

[5] Japanese sources claim the midget submarine's crew scuttled her after the B-25 attacks.

[6] In 1987, divers from MV TELITA are exploring the wreck of a sunken WW2 armed freighter off Three Islands Harbor, N of New Hanover Island. The freighter is lying on its starboard side covered in sea fans and soft corals in 22 m of water. One of TELITA divers swims out from the wreck – straight into midget submarine HA-52. The submarine is intact and sits upright only 50m from the freighter’s main masts. Salvagers had come and gone, but never suspected it was there. TELITA’s divers inspect the periscope, the twin counter rotating propellers and the empty twin torpedo tubes and open the hatch, which is not locked down. The slimmest diver is rigged with a line, torch and long hose and sent in. She gets to the bottom of the ladder and can see the sub is empty.

Midget Submarine sunk off New Hanover

Port Bow and Conning Tower

Starboard Bow & Empty TTs and Stern View

(Conning Tower Photo by Howard Sawyer, all others by Kevin Denlay)

[7] Midget HA-53 was at Rabaul at war's end. HA-53's source of transportation to Rabaul is unknown. on 17 Jan '46, she was raised by Australian Commonwealth Marine Salvage Board salvage ship CALEDONIAN SALVOR with help from the midget's former crew and handed over to the NOIC, Rabaul. Thereafter, she was allowed to deteriorate and finally scuttled in deep water. She may be the submarine that George Tyres found in 400 foot of water near KEIFUKU MARU. Later, wreck not found again due to severe seismic underwater activities.

Japanese prisoners assisting in raising HA-53 in Simpson Harbor postwar

Thanks go to Peter Cundall and to Kevin Denlay of Australia and Erich Muehlthaler of Germany for additional info on HA-53.

Special thanks for the photos of the Kavieng midget submarine go to photojournalist/divers Howard E. Sawyer of the United Kingdom and Kevin Denlay of Australia. Thanks also go to Mr. Denlay for info on the 1987 find of the midget submarine and to Bob Haldstead, ex-owner of MV TELITA and diver Kevin Baldwin who found the midget submarine.

-Bob Hackett and Sander Kingsepp

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