The Search for the World War II Japanese Midget
Submarine Sunk off Pearl Harbor, Dec. 7, 1941
Introduction
At 12.20 p.m. on August 28, 2002,
the Pisces IV and Pisces V, two deep diving
submersibles operated by the Hawaiʻi Undersea Research
Laboratory (HURL), found the Japanese midget submarine
which was the first vessel sunk in the attack on Pearl
Harbor, December 7th, 1941. HURL is one of six
national laboratories comprising NOAA's National
Undersea Research Program. It is located at the
University of Hawaiʻi's School of Ocean and Earth
Sciences and Technology. The sunken midget sub was
located during the last of a series of test and
training dives conducted annually in the military
debris fields off Pearl Harbor. HURL is now
undertaking its regular four to five month dive season
of scientific and engineering dives focusing on
fisheries enhancement , coral reef habitats, undersea
volcanism, landslide monitoring, acoustic
identification of fish and their habitats and other
engineering and oceanographic studies.
This midget sub find has been
described as the most significant modern marine
archeological find ever in the Pacific, second only to
the finding of the Titanic in the Atlantic. The
Japanese midget sub was one of five attached to five
I-class mother submarines and brought from Japan to be
launched 5-6 hours before the aerial attack, within a
few miles of Pearl Harbor. Each had a crew of two. The
subs were battery powered , 78 feet long , 6 feet in
diameter and weighed 46 tons. They carried two
torpedoes and a scuttling charge to avoid capture.
Although experimental in design, they were very
advanced for the time. For short periods, they could
run at 20 knots. These midget submarines were
completed only months before the attack allowing
little time for the crews to train. All of the five
submarines comprising the advanced attack force were
sunk or captured. The type A midget submarines had a
series of basic design problems including trim and
ballast control and problems both with battery life
and battery monitoring. Later redesign, as five man
midget submarines of the Koryu class, addressed but
did not solve these problems. The Japanese midget
submarines although believed at the time to be a
potent secret weapon, in actual fact, were never
highly effective. So far four of the five original
midget submarines attacking Pearl Harbor have been
found.
History
The discovery of the midget
submarine confirms the account radioed to naval
command at Pearl Harbor at 6:45 am on Dec. 7, 1941 . A
Japanese submarine was shot through the conning tower
and then depth charged trying to enter Pearl Harbor
behind the USS Antares. The crew of the attacking USS
Ward , an older style four stack destroyer, saw the
midget sub lifted out of the water by depth charges
after firing the fatal shot from its four inch side
gun. The Ward's crew were Naval reservists from St.
Paul, Minnesota. Unfortunately, Naval command in Pearl
Harbor ignored the Ward's report and the aerial attack
began at 8 am. At the Pearl Harbor investigation, some
question was made of the accuracy of the Ward's
report. The Ward is now vindicated. The Ward itself
was later targeted by the Japanese and sunk in a
kamikaze attack, ironically on Dec. 7, 1944, in the
Philippines.
Search
The search for the Japanese midget
sub has been ongoing for 61 years since it was first
sunk. In its latest phase, the Hawaiʻi Undersea
Research Lab has conducted towed side scan sonar
surveys of the debris fields off Pearl Harbor. At the
end of World War II, obsolete war material was dumped
in 1,000-3,000 feet of water several miles off Pearl
Harbor. This included: landing craft, tanks, old
aircraft, trucks, barges, small ships, fuel tanks etc.
There are on the order of 1,000 significant sonar
targets in the area. Sorting through these various
targets to identify the most promising ones to dive on
as a submersible pilot training exercise has been the
work of many years. The Japanese midget submarine
although giving a very clear return on the side scan
survey was interspersed with other debris on the
bottom complicating the search efforts.
Findings
The Japanese midget submarine was
found in 400 m of water about five miles off the mouth
of Pearl Harbor. As it is an historically significant
military vessel and (per agreement with the government
of Japan) a property of the U.S. federal government,
its exact location is being protected by the U.S.
State Department and heritage resource management
agencies. The submarine sits upright on the bottom and
is in amazingly good condition as shown in the photos.
Both torpedoes are still in place. The submarine has
no apparent depth charge damage but does have shell
damage on both sides of the conning tower. The port
side of the conning tower exhibits what one analyst
has identified as shrapnel holes. This would
presumably have come from the first shell fired by the
USS Ward which exploded near the submarine but did not
directly hit it. The starboard side of the conning
tower shows a hole from the 4 inch shell fired by the
side gun on the Ward as the ship steamed past.
Apparently, this shell did not explode on impact as
the midget sub conning tower is clearly still in
place. While four depth charges were dropped directly
on the midget as the Ward passed by, the charges were
set to go off at a depth of 100 feet and the submarine
was at the surface. The pressure wave created by the 4
depth charges was sufficient to fully lift the 46 ton,
78 foot midget out of the water, but did no visually
apparent structural damage. The midget sub sank from
flooding through the four inch shell hole.
Questions
A number of questions still remain
over this submarine, which was the first casualty in
the war between the U.S. and Japan. Why did the Naval
command at Pearl Harbor apparently ignore a confirmed
enemy sinking right off its harbor mouth? Why did the
Japanese put so much faith in the five midget
submarines that they were allowed to lead the Pearl
Harbor attack? After all five of the attacking midget
submarines were lost in their first engagement and
shown to be ineffective, why did the Japanese Imperial
Navy go on to build hundreds of midget submarines most
of which were never used? Regarding the site and
vessel itself: Should it ever be raised? What is its
structural integrity and deterioration rate? How
stable is its position on the seabed? How can we best
learn from the site and preserve it for future
generations?
Heritage Preservation and the Future of the Midget
Sub
Since its discovery, the Japanese
midget sub has become the focus of a concerted
research and preservation effort on the part of HURL,
NOAA, and the National Park Service. Resting in the
darkness on the seafloor, the site is a tangible
reminder of historic events which began the war in the
Pacific, and as a war grave a monument to the
sacrifices made at that time. The midget sub is most
directly connected to the Pearl Harbor National
Historic Landmark and the unique sites of the USS
Arizona and the USS Utah. Careful preservation and
study of the sub is, therefore, well warranted. NOAA's
maritime heritage management efforts feature in situ
preservation as the preferred alternative. This
approach does not ultimately prohibit intervention or
even recovery, but instead emphasizes the
precautionary approach and the need for data
collection and fully understanding the unique resource
prior to taking any action that might detrimentally
impact the site. The goal is heritage preservation and
resource protection so that future generations may
learn from and appreciate our maritime past. To this
end HURL, NOAA and the National Park Service have
entered into a joint agency collaboration and are in
the process of gathering appropriate data on site
environmental conditions, metal deterioration rates,
and stability status of the midget sub. This is an
essential step in the long term heritage management
plan for this special property. All research actions
are taken with proper regard and respect for the
site's historical significance and war grave status.
