(Captured EMB under test by an American soldier)

Explosive Motorboats based in the Philippines

© 2009-2011 Bob Hackett and Sander Kingsepp

Revision 8

26-27 July 1944:
Hawaii. President Frankin D. Roosevelt, CINC South West Pacific Area General Douglas MacArthur, Joint Chiefs Chairman Admiral William D. Leahy and CINC Pacific Ocean Areas Admiral Chester A. Nimitz attend the Honolulu Conference to decide on future American strategy in the Pacific.

MacArthur, Roosevelt, Leahy and Nimitz at Honolulu
(National Archives)

MacArthur argues that the United States must liberate the Philippines without further delay. Nimitz argues for bypassing the Philippines and assaulting Formosa. MacArthur counters that with Philippines under Allied control, Japan will be cut off from access to Dutch East Indies oil and other resources and that all Japanese troops south and west of the islands will be isolated. Privately, MacArthur reminds the President that if America does not honor her commitment to liberate the Philippines, "the American electorate will rise up in righteous indignation and vote you out of office."

The plan, as later approved, calls for MacArthur's forces to attack Mindanao, Philippines and those forces under Nimitz to strike the island of Yap. The two forces would then be combined to assault Leyte. MacArthur's forces would next invade Luzon, after which Nimitz's forces would move against Iwo Jima and Okinawa.

August 1944:
Yokosuka Naval Base. The 6th Shinyo Squadron is formed with a strength of 200 men and 48 Type 1 Shinyo Explosive Motorboats (EMBs). IJN plans call for the construction of Shinyo surface raiding bases at Davao and Sarangani Bay on Mindanao, at Tacloban on Leyte and Lamon Bay on Luzon.

September-October 1944:
Over 1,000 IJN Shinyo EMB and IJA "Maru-ni" EMBs are transported to the Philippines, but enroute the 14th, 15th and 39th Shinyo Squadrons are lost at sea to American submarines.

Early in September, the boat units and maintenance personnel begin arriving on Luzon, but the projected bases in the southern and central Philippines are not completed in time to permit deployment before the invasion of Leyte in October. By the end of September, a special attack (suicide) unit with 70 Shinyo boats arrives at Corregidor in Manila Bay. In October, the remainder of the Imperial Navy's 300 Shinyo are off loaded in crates at Manila for assembly and deployment at Corregidor.

The Imperial Army's 800 Maru-ni are deployed to cover possible invasion beaches in Luzon. The surface raiding forces are concentrated at four main points of anticipated invasion-Lingayen Gulf, Manila Bay, Batangas. At the time of the Allied invasion of Luzon, about 150 surface raiding boats were based at Sual, on Lingayen Gulf.

Corregidor Island
(U.S. Army)

13 September 1944:
Aircraft of Admiral William F. Halsey’s Third Fleet sortie against Mindanao and other areas of the Philippines, but encounter little opposition. Based on this and other intelligence, Halsey recommends to Admiral Nimitz that the proposed invasion of Mindanao on 25 October 1944 be cancelled in favor of a direct strike on Leyte. With General MacArthur’s concurrence, Halsey’s plan goes forward.

15 September 1944:
Hotel Frontenac, Quebec. Halsey’s suggestion is adopted at the Second Quebec (codenamed OCTAGON) conference and the invasion date for Leyte is set for 20 October 1944. This requires Nimitz’ amphibious force to be diverted to Leyte rather than assaulting Yap.

Roosevelt and Churchill with American and British Combined Chiefs of Staff at Quebec
(Seated) Gen. George C. Marshall, Admiral William D. Leahy, Roosevelt, Churchill, Field Marshal Sir Alan Brooke, Field Marshal Sir John Dill
(standing) MajGen L. C. Hollis, Gen Sir Hastings Ismay, Admiral Ernest J. King, Marshal of the RAF Sir Charles Portal, Gen Henry H. Arnold, Admiral Sir Andrew B. Cunningham.
(National Archives)

(U.S. Army)

October 1944:
The 6th Shinyo Squadron, that arrived at Manila aboard two unidentified oil tankers, is based at Zamboanga, Mindano. Under continous threat of American air attacks, the squadron is withdrawn from Zamboanga and transported to Sandakan, N Borneo. [1]

1 October 1944:
Convoy HI-77 departs Moji consisting of transports MANJU (SANTOS), and 10 ships escorted by four kaibokan. MANJU MARU is carrying elements of Lt Yamazaki’s 7th Shinyo Squadron

8 October 1944:
Captain Agawa Ryosaburo’s transport ASAMA MARU departs Moji for Shanghai escorted by kaibokan OKINAWA and torpedo boat SAGI. ASAMA MARU carries about 5,000 army and navy troops including 246 men of the 9th Shinyo Unit's base force and 50 IJA "Maru-yon” explosive motorboats and 50 pilots for these boats.

10 October 1944:
Vice-Admiral (later Admiral) Marc A. Mitscher's (former CO of HORNET, CV-8) Task Force 38 launches the first strikes on Okinawa for the pre-invasion landings on Leyte, Philippines.

16 October 1944:
At 1820 convoy MOMA-05 departs Imari Bay carrying about 10,000 reinforcement troops for the Philippines. The convoy consists of DORYU, TATSUURA and SUGIYAMA MARUs and eight other ships escorted by a kaibokan and four subchasers. SUGIYAMA MARU carries Lt Ishii Sumio’s 8th Shinyo Squadron. TATSUURA MARU departs Sasebo carrying elements of Lt Ishikawa Makoto’s 10th Shinyo Squadron. DORYU MARU carries Lt Nakajima Ryojiro’s 11th Shinyo Squadron.

20 October 1944: American Operation "KING TWO" - The Invasion of Leyte, Philippines:
Admiral (later Fleet Admiral) William F. Halsey's (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, lands the Army's X Corps (24th Infantry and 1st Cavalry Divisions) and the XXIV Corps (7th, 77th and 96th Infantry Divisions) that begins the campaign to retake Leyte.

MacArthur Returns
(U.S. Army)

26-31 October 1944:
Enroue to Manila, convoy MOMA-05 is attacked by USS DRUM (SS-228), ICEFISH (SS-367) and GUITARRO (SS-363). The three American submarines sink five marus in the convoy that take down about 5,700 IJA troops and 144 crewmen including gunners.

1 November 1944:
At 0400, convoy MOMA-05 arrives at Manila and disembarks the 8th and 10th Shinyo Squadrons. Later, the 8th Shinyo Squadron is based at Legaspi, Luzon and the 10th Shinyo Squadron is deployed to defend Corregidor Island. At 1800, that same day, convoy MOMA-06 departs Takao for Manila consisting of transports ATLAS MARU and ten other ships escorted by fleet supply ship KURASAKI, a destroyer, three kaibokan, a minesweeper and a subchaser. ATLAS MARU is carrying a deck cargo of Lt Kojima Suiyoshi's 13th Shinyo Squadon's 50 Type 1 EMBs to defend Corregidor Island and 1,325 troops and passengers.

2 November 1944:
Off Sabtang Island, Bashii Strait, Philippines. At 2305, LtCdr John B. Hess’s (USNA ’37) USS POMFRET (SS-391) torpedoes and damages ATLAS MARU. About 1330, on 4 Nov '44, ATLAS MARU is beached and her cargo begins to be unloaded. Salvage proceeds the next four days until a typhoon forces all efforts to be abandoned. The 13th Shinyo Squadron loses an unknown number of its 50 EMBs and an unknown number its 187 men.

10 November 1944:
GYOKUYO and SHINFUKU MARUs depart Miike, Kyushu for Manila in convoy MOMA-07 also consisting of nine other ships escorted by four kaibokan an auxiliary subchaser and an unidentified warship. GYOKUYO MARU is carrying men and EMBs of the 14th and 15th Shinyo Squadrons to be based in the Philippines. SHINFUKU MARU carries elements of Lt Matsuda Yoshihisa's 12th Shinyo Squadron and arrives at Manila on 15 Dec ‘44. Later, the 12th Shinyo Squadron is dispatched to defend Corregidor Island.

12 November 1944:
248 miles SW of Nagasaki. At 0420, LtCdr (later Rear Admiral/MOH) Eugene B. Fluckey’s (USNA ’35) USS BARB (SS-220) torpedoes GYOKUYO MARU and she goes dead in the water. Later, JINYO MARU attempts a tow, but the towline parts. The passengers are transferred to other ships.

At 1800, that same day,convoy TAMA-31B departs Takao for Manila consisting of MANJU MARU and six other ships escorted by two patrol boats. MANJU MARU, that left Moji on 1 Oct ’44 is still carrying the 7th Shinyo Squadron.

14 November 1944:
LtCdr Gordon W. Underwood's (USNA ’32) USS SPADEFISH (SS-411) torpedoes and sinks GYOKUYO MARU, previously damaged by BARB, at 31-04N, 123-56E. She takes down an unknown number of men and Type 1 EMBs of the 14th and 15th Shinyo Squadrons.

USS SPADEFISH at Mare Island Navy Yard, 1944

15 November 1944:
LtCdr (later Rear Admiral) Charle's E. Loughlin's (USNA ’33) USS QUEENFISH (SS-393) attacks convoy HI-81 enroute to the Philippines. QUEENFISH sinks AKITSU MARU. She takes down 2,246 soldiers and crew including the IJA's 20th Sea Raiding Battalion and probably all of its "Maru-Ni" EMBs.

17 November 1944:
LtCdr Evan T. Shepard's (USNA ’35) USS PICUDA (SS-382) attacks convoy HI-81 enroute to the Philippines. PICUDA sinks MAYASAN MARU. She takes down 3,546 soldiers and crew including the IJA's 24th Sea Raiding Battalion and probably all of its maru-ni EMBs.


21 November 1944:
At 1500, TAMA-31B and the 7th Shinyo Squadron arrive at Manila.. Later, the 7th SS is sent to Corregidor.

29 November 1944:
108 miles off Omae-zaki, Honshu. At 0309, Cdr (later Captain) Joseph F. Enright’s (USNA ’33) USS ARCHER-FISH (SS-311) hits partially completed supercarrier SHINANO (YAMATO class hull) with four torpedoes starboard side. Incomplete fittings allow flooding to spread and a heavy list to starboard develops. At 1018, Abandon Ship is ordered and at 1057 SHINANO capsizes to starboard and sinks by the stern at 33-07N, 137-04E, taking down 1,435 officers and men, 50 “Ohka” rocket bombs and six Shinyo EMBs ultimately bound for the Philippines and Okinawa.

November 1944- January 1945:
Altogether, the 7th, 9th, 10th, 11th and 12th Shinyo Squadrons arrive with a strength of 300 Type 1 EMBs to defend Corregidor.

2 December 1944:
LtCdr Ralph C. Styles' (USNA ’33) USS SEA DEVIL (SS-400) attacks convoy MI-29 enroute to the Philippines. SEA DEVIL sinks 9,467-ton transport HAWAII MARU. She takes down 2,047 soldiers and crew including the IJA's 22nd Sea Raiding Battalion and probably all of its maru-ni EMBs.


At 2240, convoy TAMA-33 arrives at Manila consisting of Army landing craft depot ships SHINSHU and KIBITSU MARUs escorted by kaibokan TSUSHIMA and DAITO, CD-14, CD-16, CD-134, CD-46 and minesweeper W-101. SHINSHU MARU lands 100 Army maru-ni EMBs and elements of the 18th and 19th Sea Raiding Battalions.

20 December 1944:
Captain Itagaki Akira (47)(former XO of KINUGASA) of the 31st Special Base Force is assigned as director of the Manila Bay Entrance Defense Force, with LtCdr Koyameda Shoichi as commander of the surface special attack (suicide boat) unit.

23 December 1944:
Captain Itagaki sends a message to the Shinyo squadrons on Corregidor that reads "the enemy fleet is moving north from the Mindoro area, with the possibility of attacking Corregidor." Itagaki orders the Shinyo squadrons to sortie. While preparing to set out, a fire starts in the gasoline engine of one of Lt Nakajima Kenjiro's 9th Shinyo Squadron's boats that sets off its on-board explosives. Flames jump quickly from one boat to another packed tightly in a cave. In the end, 50 boats are destroyed and 100 of their pilots die in the disaster.

7 January 1945:
Malinta Tunnel (former HQ of Gen MacArthur), Corregidor. Mines stored inside the 835-foot tunnel accidentally blow up one after another and take the lives of many men.

Malinta Tunnel, Corregidor
(U.S. Army)

9 January 1945: The Invasion of Luzon, Philippines:
Vice Admiral (later Admiral) Thomas C. Kinkaid's Task Force 77 lands Lt General (later General) Walter Krueger's Sixth Army troops at Lingayen Gulf under cover of heavy gunfire from Vice Admiral (later Admiral) Jesse B. Oldendorf's TG 77.2 bombardment force and aircraft from the Rear Admiral (later Vice Admiral) Calvin T. Durgin's TG 77.4 escort carrier force. Initially, the troops encounter little resistance, but Japanese air attacks and EMBs continue to attack the invasion forces off the beaches.

9/10 January 1945:
Lingayen Gulf. That night, about 70 Imperial Army maru-ni EMBs launch a mass attack against American invasion shipping in Lingayen Gulf. USS ROBINSON (DD-562) of the Attack Force screen is anchored in the transport area. She comes under a pre-dawn attack by an EMB that drops depth charges. The explosions temporarily put ROBINSON's sonar equipment out of commission, but do no other serious damage.

IJA maru-ni EMB
(U.S. Army)

At 0410, auxiliary transport WAR HAWK (AP-168) suddenly shudders heavily as a maru-ni EMB, going full-throttle and laden with explosives, crashes into her port side. The explosion tears a 26-foot hole in No. 3 hold and kills 61 men. WAR HAWK lay without power and an engine room begins to flood. Her repair crews work to restore power and patch the ship's side while WAR HAWK’s gunners fight to repel air attacks. The transport then disembarks her remaining troops and begins unloading her embarked mechanized equipment. On 11 January, she creeps to Leyte Gulf.

Transport WAR HAWK (AP-168)
(U.S. Navy)

During the dark early morning, USS PHILIP (DD-498) picks up a small boat on radar which she challenges. The small craft, acting queerly, does not reply. After illuminating the maru-ni EMB with her searchlights, PHILIP opens fire with her 20-mm guns and hand-held .45 sub-machine guns. The boat turns sharply and heads directly for the destroyer's port side amidships, but is exploded by 20-mm gunfire just 20 yards short of her mark.

Maru-ni EMBs infiltrate the transport areas and sink infantry landing craft (mortar) LCI (M)-974 (Landing Craft Infantry-Mortar) at 16-06N, 120-14E. Infantry landing craft (gunboat) LCI (G)-365 is hit by an EMB. Only a few men are injured, but the ship is out of action for the rest of the war. Maru-ni EMBs also damage landing ship tank LST-610.

Lingayen. LST-925 and LST-1028 (Landing Ship Tank) are seriously damaged by depth charges dropped by Maru-ni EMBs. They are beached and lay at right angles to each other. All 70 maru-ni EMBS are destroyed during the raid.

LST-925 and LST-1028 grounded on Orange Beach, Lingayen Gulf
(U.S. Navy)

24 January 1945:
More American planes attack and bomb Corregidor. Twenty-five Shinyo EMBs are destroyed. The remaining EMBs of the Shinyo squadrons are moved into Malinta tunnel.

30 January 1945:
Corregidor reports to Captain Itagaki that about 100 Shinyo EMBs remain. The rest, about 200 boats, had been destroyed. Lt Ishikawa's 10th Shinyo Squadron is ordered to attack an island south of Corregidor, but the mission cannot be completed and they return.

31 January 1945:
A Shinyo Squadron, recently established at Balayan Bay, is ordered to sortie against Rear Admiral (later Admiral) William M. Fechteler’s TG 78.2 that landed Army troops to outflank Japanese forces defending Manila (Operation Mike Six). Rear Admiral William D. Sample’s TG 77.4 provides cover.

Subchaser PC-1129
(U.S. Navy)

S of the entrance to Manila Bay. At about 2235, subchaser PC-1129 detects the EMBs approaching and radios the alarm. The Shinyo EMBs overwhelm PC-1129 from all angles. The subchaser's 3-inch and 40mm AA guns blast apart two EMBs, but a third rams PC-1129 amidships and explodes tearing a six-foot hole in her hull at the waterline. The subchaser capsizes and sinks at 14-05N, 120-30E.

15 February 1945:
At about 0845, signals are received by the Shinyo Squadron that read: "enemy landing boats, 8 large and about 40 small are approaching the north shore," and "the enemy is estimated to land west of Mariveles." At 2100, Special Attack Commander Koyameda orders Lt Matsuda's 12th Shinyo Squadron to "attack and destroy the enemy fleet stationed in Subic Bay."

16 February 1945:
At 0315, about 30 Shinyo EMBs depart Corregidor and appear suddenly in the port of Mariveles. LCS (L)(3)-26 (Landing Craft Support, Large, Mk 3)-7, LCS (L)(3)-8, LCS (L)(3)-26, LCS (L)(3)-27, LCS (L)(3)-48 and LCS (L)(3)-49 are anchored across the mouth of Mariveles Bay. In the pre-dawn darkness, the flotilla of EMBs roars toward the U.S. task force. One EMB slams into LCS(L)(3)-26 and explodes. Many of LCS (L)(3)-26's crewmen abandon ship and jump into the water. Suddendly, a second suicide boat rams the vessel and creates a fiery conflagration. 76 men are KIA. LCS (L)(3)-7 and LCS (L)(3)-49 are also sunk. LCS (L)(3)-27 and another LCS (L)(3) are damaged in the attack. Most of the EMBs are destroyed.

Typical Landing Craft Support, Large, Mk 3
(U.S. Navy)

The American 503d Parachute Infantry is air-dropped onto the main plateau on Corregidor, while the 3d Battalion, 24th Regimental Combat Team (RCT) is lifted to the island in navy medium landing craft (LCM). Support landing craft (large) [LCS(L)] and infantry landing craft (rocket) [LCI(R)] provide close-in covering fire.

Shinyo EMBs at Corregidor
(U.S. Army)

The five remaining boats of the 10th Shinyo Squadron are ordered to set out for the follow-up attack. However, due to the landing of American parachute troops and the landing from the south dock that same day, the chance for a second attack is lost.

17 February 1945:
Captain Itagaki is KIA. He is promoted Rear Admiral, posthumously.

24 February 1945:
Japanese resistance in Manila ceases.

During the course of the war, in addition to the loses at sea of men and EMBs previously mentioned, the Philippines-based 8th Shinyo Squadron looses 99 men, the 9th looses 244 men of an originally authorized 184, the 10th looses 138 men, the 12th looses 131 men, the 13th looses 79 men, the 14th looses 100 men and the 15th Shinyo Squadron looses 121 men, all to unknown causes, most probably including accidents, bombings and ground action.

Shinyo EMBs at Samar

3 September 1945:
Philippines High Commissioner’s Residence at Baguio. At 1210, in his former residence and headquarters, LtGen Yamashita Tomoyuki (the “Tiger of Malaya”) signs the document of unconditional surrender of all Japanese forces in the Philippines. MajGen W.H. Gill, CG, 32nd Division accepts the surrender. [2][3]

The senior American officer present is LtGen (later Gen/MOH) Jonathan M. Wainwright, who surrendered the Philippines to the Japanese in 1942. British LtGen Sir Arthur Percival, who surrendered Singapore to Yamashita in 1942 is also present.

LtGen Yamashita surrenders the Philippines

Authors’ Notes:
Japanese records seldom detail individual EMB attacks. While U.S. wartime records describe EMB attacks, they most often do not distinguish between the IJN's "Shinyo" and the IJA's "Maru-ni". In some cases, therefore, our TROMs simply refer to both service's suicide boats as "EMBs".

[1] As a result of the 17 October 1944 invasion of Leyte, the 6th Shinyo Squadron was trapped at Sandakan for the duration of the war.

[2] Wainwright is seated at the left on the far side of the long dining room table. Yamashita is seated in the middle at the near side of the table. Vice Admiral Okawachi Denshichi (37) CinC, Southwestern Area Fleet, is seated at the far right. Percival is partially obscured by the man standing and the unidentified Japanese at the left.

[3] Yamashita surrendered his Shin-Gunto samurai sword (with general officer's knot) dating to about 1640-1680. Okawachi also surrendered his Kai-Gunto sword at the ceremony. Yamashita’s sword is now at the U.S. Military Academy at West Point and Okawachi’s is at the U.S. Naval Academy at Annapolis. Yamashita was convicted of war crimes and hanged on 23 Feb '46 at Bilibid Prison, Philippines.

Thanks go to John Whitman of Virginia for info about the loss of the IJA's 20th, 22nd and 24th Sea Raiding Battalions and info on the 7th Shinyo Squadron. Thanks also go to Akira Takizawa of Japan for help with Rev 6. Thanks again go to John Whitman, Erich Muehlthaler of Germany and Gengoro S. Toda of Japan for help with Rev 8.

-Bob Hackett and Sander Kingsepp

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