Explosive Motorboats

SHINYO!

(Captured EMB under test by an American soldier)

Explosive Motorboats based in the Philippines 1944-1945
By Bob Hackett and Sander Kingsepp

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 Explosive Motorboats (EMB). IJN plans call for the construction of Shinyo surface raiding bases at Davao and Sarangani Bay on Mindanao, at Tacloban on Leyte, and at 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, and Lamon Bay. 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 [1] (National Archives)

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. [2]
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.
Philippines (U.S. Army)

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)

1 November 1944:
Lt Yamazaki’s 7th Shinyo Squadron, Lt Nakajima Kenjiro’s 9th, Lt Ishikawa Makoto’s 10th, Lt Nakajima Ryojiro’s 11th, Lt Matsuda's 12th and Lt Ando's 13th Shinyo Squadrons are positioned on Corregidor Island with a strength of 300 Type 1 EMBs. Lt Ishii Sumio’s 8th Shinyo Squadron is based at Legaspi, Luzon.
2 November 1944:
Off Sabtang Island, Bashii Strait, Philippines. At 2305, LtCdr John B. Hess’s USS POMFRET (SS-391) attacks convoy MOMA-06 enroute from Takao to Manila. POMFRET torpedoes and damages ATLAS MARU carrying a deck cargo of Shinyo EMBs and 1,325 troops and passengers.
4 November 1944:
At about 1330, ATLAS MARU is beached and her cargo begins to be unloaded (by 18 November, a typhoon causes ATLAS MARU to be abandoned).
29 November 1944:
108 miles off Omae-zaki, Honshu. At 0309, Cdr Joseph F. Enright’s 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 develops. At 1018, Abandon Ship is ordered and at 1057 SHINANO sinks at 33-07N, 137-04E, taking down 1,435 officers and men, 50 “Ohka” rocket bombs and 6 Shinyo EMBs that were bound for the Philippines and Okinawa.
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 Ken's 7th 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.

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] (Seated) Gen. George C. Marshall, Admiral William D. Leahy, Roosevelt, Churchill, Field Marshal Sir Alan Brooke, Field Marshal Sir John Dill; (standing) Maj. Gen. 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.
[2] 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.
-Bob Hackett and Sander Kingsepp

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