(Captured EMB under test by an American soldier)

Battle Histories of Japan's Explosive Motorboats

26 November 2011

By Bob Hackett and Sander Kingsepp

Discussion & Questions

In 1937, Japanese hull designers began a study of existing British, Italian and American motor and torpedo boats. Many models were made. By 1941, they completed their own design of six 18-meter motor torpedo boats. At the beginning of the war, these models were put into production.

In March 1944, the Shinyo ("Sea Quake") manned explosive motorboat (EMB) program was begun. The first models were copied from the 18-meter motor torpedo boats. Six steel hulled boats were constructed at Yokosuka Naval Base and two wooden hulled EMBs were built at Tsurumi, Yokohama.

On 27 May 1944, the first Shinyo EMBs were tested. Difficulties were encountered with the design and it was determined to abandon steel hulls in favor of wooden hulls because of the availability of materials.

On 1 August 1944, over 400 new students arrived at the Naval Torpedo School facility at Kawatana on Omura Bay, near Yokosuka. Captain Hara Tameichi (former CO of DesRon 27) was Senior Instructor. The students, all would-be aircraft pilots, had been transferred from aviation schools because of the lack of aircraft production. Their average age was 17 years. The students were given the choice of training for duty with conventional torpedo boats, Special Attack (suicide) boats or as suicide frogmen. About 150 of the first students chose the Special Attack EMBs.

A three-month training period in small-boat handling, mechanics and attack techniques was prescribed for EMB units, but the early squadrons were soon deployed in the defense of the Philippines, Okinawa, Formosa and Hainan Island. In September 1944, the 1st, 2nd and 5th Shinyo Squadrons were sent to Chichijima in the Bonin Islands, the 3rd and 4th Shinyo Squadrons to Hahajima, Bonins, while the 6th Shinyo Squadron went to the Philippines. In October-November 1944, EMB training "officially" commenced.

Type 1 one-man Shinyo EMBs were relatively slow and only capable of speeds up to about 23 knots. When carrying a warhead, their top speed dropped off to a dismal 18 knots. Typically, Navy EMBs were equipped with a bow-mounted explosive charge. Army EMBs carried two depth charges and were not considered suicide boats, as the pilot was supposed to drop the depth charges and U-turn around in the 6-seconds before they exploded. In reality, there was no way to get away safely from the explosion.

The slightly larger and faster two-man Type 5 Shinyo EMBs were powered by two automobile engines. Armed with a 13.2mm heavy machine gun, they were designed to serve as command boats. Both Type 1 and Type 5 Shinyo were equipped with two 120-mm RO-SA rockets (same type used on ISE and HYUGA, not rocket guns) to increase speed during the final run-in and as makeshift propulsion in case of engine failure. The engine(s) for both versions was designated as Toyota KC Special Type. Some Type 5 Shinyo were equipped with radio telephones.

A total of 6,197 Shinyo EMBs were manufactured for the Imperial Japanese Navy and 3,000 somewhat similar "Maru-ni" EMBs for the Imperial Japanese Army. Around 1,100 boats were transported to the Philippines, 400 to Okinawa and Formosa, and smaller numbers to Korea, Shanghai, Hong Kong, Hainan and Singapore. The vast majority of EMBs were stored along he shores of coastal Japan for defense against the expected invasion of the Home Islands. The Naval General Staff expected a 10 percent hit rate for Shinyo EMBs.

EMBs scored some limited successes in the Philippines and Okinawa, but heavy gunfire from Allied ships and PT-boats ("fly-catchers") stopped most of them. Others were lost in transit, met with accidents, or were strafed and sunk by American aircraft.

No detailed production records of EMBs have been located by the authors; however, Japanese and Allied records do contain some information concerning EMB operations. As a result, although we cannot present EMB data in our usual Tabular Record of Movement (TROM) format, we have chosen to present the information by geographical areas of operation and time periods as listed below.

Philippines, 1944-1945
(Revised 8/6/2011))

Formosa (Taiwan) and the Pescadore Islands, 1944-1945
(Posted 11/26/2011)

Ogasawara (Bonin) Islands, 1944-1945
(Posted 8/28/2010)

North Borneo, 1944-1945
(Posted 9/4/2010)

Hainan Island, China, 1944-1945
(Posted 6/17/2011)

Amoy (Xiamen), China, 1945
(Posted 7/9/2011)

Okinawa, 1945
(Revised 1/29/2011)

Hong Kong, 1945
(Revised 1/29/2011)

Saishu-To (Quelpart) Island, 1945
(Posted 1/29/2011)

Shanghai, China, 1945
(Posted 7/16/2011)

Japan, 1945
(Posted 10/31/2009)

Bibliography of Sources

About the Authors

Mr. Robert D. Hackett is a military historian and researcher. Retired from the United States Air Force and later from the aerospace industry, he resides in Florida.

Mr. Sander Kingsepp of Estonia is also a military historian and researcher. A free-lance writer and talented linguist, Sander's translations of Japanese source materials have added immeasurably to these TROMs.

Questions to the authors concerning these TROMs should be posted on the Discussion and Questions board.