The Search for the World War II Japanese Midget Submarine Sunk off Pearl Harbor, Dec. 7, 1941
John C. Wiltshire, Ph.D.
Hawaii Undersea Research Laboratory
School of Ocean and Earth Sciences and Technology
University of Hawaii, Honolulu
(click to view images)
At 12.20 p.m. on August 28, 2002, the Pisces IV and Pisces V, two deep
diving submersibles operated by the Hawaii 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 Hawaii'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.
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.
The search for the Japanese midget sub has been ongoing for 61 years since
it was first sunk. In its latest phase, the Hawaii 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.
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.
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
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.
As we learn more about what will become of the Japanese midget submarine, we will post it on this website.
All images are the property of the HURL Data Dept. Please contact Rachel at 808-956-6183 if you would like to work out an agreement to use any photos or video of this midget submarine. Please be aware that there will be a fee involved.