(Captured EMB under test by an American
Battle Histories of Japan's Explosive Motorboats
26 November 2011
By Bob Hackett and Sander Kingsepp
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.
Formosa (Taiwan) and the Pescadore Islands, 1944-1945
Ogasawara (Bonin) Islands, 1944-1945
North Borneo, 1944-1945
Hainan Island, China, 1944-1945
Amoy (Xiamen), China, 1945
Hong Kong, 1945
Saishu-To (Quelpart) Island, 1945
Shanghai, China, 1945
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.