The Final Battle:
Okinawa’s Underground Defense
By: J.D. Haines, LCDR,MC,USNR
The Battle of Okinawa is often remembered as the final battle of World
War II. From April 1, 1945 to June 22, 1945, the armed forces of America and
Japan proved what both sides had known at the outset: the victor would have to
utterly destroy his opponent. When the smoke cleared, over 76,000 Japanese
soldiers were dead; over 6,000 Americans were killed, with over 66,000 wounded
or ill; and over 122,000 Okinawan civilians lay dead. The civilian casualties
amounted to one-third of the indigenous population of the island, rivaling the
immediate death toll of over 120,000 at the atomic bombings of Hiroshima and
Nagasaki.
Pfc. Paul Isom of the 5th Marine Division dashes madly across Okinawa’s “Death Valley” as the
Americans press their assault against the Japanese bastion.
Image Credit: NATIONAL ARCHIVES
As the war in the Pacific resulted in continued Allied success, the
Japanese Empire believed that losing Okinawa, just 320 miles from the
Japanese home islands, would be disastrous. The Americans sought Okinawa
for several strategic reasons. First, American bombers could easily reach the
Japanese home islands from Okinawa. Second, capture of Okinawa would sever
vital supply lines to Japan. And last, Okinawa could be used as a support base
for the planned Allied invasion of the Japanese mainland (scheduled for
November, 1945).
The Japanese Imperial Army and Navy had, roughly, a year to prepare for
the anticipated American invasion. This allowed the preparation of ingenious
underground defenses, impervious to shell fire and aerial bombing, that resulted
in some of the bloodiest fighting of WWII.
During the Japanese troop build-up to defend the island, he elite Imperial
Army 9th Division was ordered to transfer from Okinawa to bolster defenses in
the Philippines. This forced the Japanese military leaders in Okinawa to
abandon plans for an offensive strategy -- seeking out the enemy in close
combat – and replace it with a defensive strategy, since the overwhelming
superiority of American forces and firepower would quickly annihilate any
Japanese forces who fought in the open.
A member of the 1st Marine Division draws a bead on a Japanese sniper with his Thompson
submachine gun as his companion ducks for cover. The division attacked Wana Ridge before
moving on to the town of Shuri. Image Credit: NATIONAL ARCHIVES
In overall command of the Imperial Japanese Army was Lt. General
Ushijima Mitsara, a conservative consensus-builder. His Chief of Staff was
General Cho Isamu, a heavy drinker who enjoyed Scotch whisky and good food.
When inebriated, he often entertained fellow officers by performing his trademark
Samurai sword dance. Colonel Yahara Hiromichi was the operations officer,
known as a dour, aloof, preoccupied intellectual. Together, however, the three
diverse commanders functioned remarkably well. Their combined efforts
produced one of the most effective Japanese defensive fights of the entire Pacific
War.
Colonel Yahara devised a plan of concentrating Japanese forces in the
strategically critical and more defensible southern part of Okinawa. The island,
just 64 miles long and from two to 18 miles wide, had numerous caves and other
natural features that the Japanese cleverly employed in constructing defenses.
Colonel Yahara initiated an ambitious campaign of digging enough tunnels and
caves to move the entire 32d Army and its supporting Navy troops underground.
“Confidence in victory will be born from strong fortifications,” became the
rallying cry as work on caves and tunnels progressed. The fortifications would
prove to be essential in defending against the superior numbers and technology
the Americans brought to bear.
A platoon of Marines works its way up a draw recently bombarded by mortars and artillery. Many
people believe the Battle of Okinawa contributed greatly to President Truman’s decision to drop
the atomic bomb on Japan. Image Credit: NATIONAL ARCHIVES
Remarkably, the Japanese were able to construct approximately 60 miles
of tunnels and innumerable caves with no mechanized tunneling equipment or
bulldozers -- entrenching tools and shovels wielded by Okinawan and Korean
slave laborers accomplished the monumental task. Since there was little cement
and no ironworks available, wooden beams for supports had to be cut from the
forests in the north of the island and transported south with great difficulty.
The underground defenses constructed on the island proved chiefly
responsible for protracting the battle, forcing American Soldiers and Marines to
blast or burn out Japanese defenders from every spider hole, tunnel complex and
cave. Lurking in underground fighting positions that were often sited on the
reverse slopes of hills (protecting them from U.S. direct fire weapons and making
them nearly invisible to attacking Americans), Japanese soldiers harried their
attackers, frequently popping up in the rear of advancing units. American troops
devised so-called “Blowtorch and Corkscrew” tactics to burn and blast the
dogged defenders from their underground positions. “Blowtorches” were tankmounted and man-portable flame throwers and “Corkscrews” were satchel
charges of high explosives. Both weapons had to be used extensively to root out
the Japanese, most often one at a time. GI casualties were horrendous.
Three members of the 6th Marine Division attempt to smoke out a Japanese soldier in a spider
hole behind some jagged coral boulders. Image Credit: NATIONAL ARCHIVES
The most elaborate of the Japanese underground bastions was the
headquarters for the Imperial Japanese Army (IJA), far below Okinawa’s ancient
Shuri Castle. This tunnel complex ran 1280 feet north and south. There were
also nearby caves for the 5th Artillery and the 62d Division HQ. The 32d Army’s
command cave lay directly beneath Shuri castle, 160 feet below the surface at its
deepest point.
The HQ cave had plank walls, offices with electricity and bunk areas
similar to those found on warships. The caves were far from comfortable,
however. Temperatures hovered around 90 degrees with nearly 100-percent
humidity. The command tunnel housed over 1,000 troops in cramped, miserable
conditions.
Each combat unit was responsible for constructing its own caves. Simple
supply caves contained food and ammunition. Nearby caves and fighting
positions were often linked by tunnels. Infantry units often installed themselves
in pillbox caves, built into hillsides. Many of the caves were under the dome of a
hill, with exits in the sides and rear of the dome. Historian Thomas Huber of the
U.S. Army’s Combat Studies Institute noted in Japan’s Battle of Okinawa: April –
June 1945, “The cave positions on Okinawa were a defensive masterpiece,
resistant to all fire, except a direct hit in the gunport.” (To read the full text of Dr.
Huber’s Leavenworth Paper on the Battle of Okinawa, go to: http://wwwcgsc.army.mil/carl/resources/csi/Huber/Huber.asp )
After the armada of 1,300 warships steamed into Okinawan waters and
put ashore the Army and Marine landing force on L-day, April 1, 1945, U.S.
forces soon discovered that the lack of Japanese resistance at the beachhead
was a cruel, “April Fool’s” joke. Taking the island from the subterranean
Japanese defenders turned into one of the most formidable tasks of the Pacific
war.
It took the Americans nearly two months before they finally overcame the
fiercely defended Shuri line on May 31, 1945. Yet, the battle was far from over.
The remaining Japanese retreated to the far south of the island and literally
fought to the death. Historian Huber notes that, “The army’s final drama was
played out in microcosm by the Okinawa Naval Base Force on Oruku Peninsula
from 26 May to 13 June.”
April 21, 1945. Flame-throwing tanks of the 7th Infantry Division burn out enemy positions on Hill
178 while infantrymen crouch low and await the order to mop up.
Image Credit: NATIONAL ARCHIVES
The Naval Base Force, commanded by Rear Admiral Ota Minoru, defended the
naval port and air station. Elaborate seaward coastal defenses in cave
emplacements had been constructed prior to the American invasion.
Approximately 10,000 Imperial Japanese Naval Officers and sailors and
Okinawan Home Guards comprised Ota’s force. On June 4, the 6th US Marines
landed on Oruku’s north coast and a pitched battle ensued as the Marines faced
caves and well-sited machine gun nests as they had on the Shuri line. The
Japanese Naval forces converted 200-mm naval guns to use against American
tanks and fired 200-mm anti-ship rockets into the Marines’ lines. The Marines
pushed the Japanese Naval Base Force down the peninsula and encircled it on
June 11. Admiral Ota then sent his farewell telegram to the 32d Army,
commending the Okinawan people’s self-sacrifice and cooperation during the
battle.
As the end of the battle neared on June 22, Ushijima and Cho also
committed suicide, just days after Ushijima’s American counterpart, Lt. Gen.
Simon B. Buckner, commander of the Tenth US Army, had been killed by
Japanese anti-tank gun fire while observing the advance of a Marine regiment.
This rare event – the deaths of both opposing commanders – is another
“landmark” in the Pacific war’s final battle.
Okinawa Today – The Remains of War
The former Japanese Navy underground HQ can be visited by the public.
Marks made by the construction party’s pickaxes can still be seen on the walls
and ceilings. Traces of the mass suicide by Ota and his men are visible by the
traces of hand grenade blast scars on the walls. The farewell message left by
Ota on a wall remains clearly visible.
In March, 1970, the Okinawa Tourism Board removed the remains of the
dead soldiers and restored 275 meters of the original 450 meters of the naval
headquarters tunnels. The commander’s room, storerooms, medical room, petty
officers’ rooms, code rooms and others have been restored.
Only the entrances to the Imperial Army’s tunnels can be viewed at Shuri
Castle.
How to get there: Take Hwy 58 south to Naha, over Meiji Bridge, and turn south
onto Route 7 at the Yamashita intersection. Go about 2.5km and turn right
across the street from a park. Follow this road uphill and take the right fork into
the parking lot of the IJN HQ. The facility is open daily from 0830-1700 and
charges admission of 380 yen for adults and 210 yen for children.
Lt. Cdr. J.D. Haines, US Navy officer and board certified family medicine
physician, is currently stationed on Okinawa with the 3rd Marine Division. He has
published over 150 articles in historical and medical journals, including the ACG
web article, “What Really Killed Stonewall Jackson.”