Explosive Find:  The Special Attack Tunnels of Miyakojima


“With back hunched, pushing forward the control stick, now comes an end to many countless hopes.”  ~Japanese Suicide Pilot’s last words

I’ve learned while exploring the world to stop and check out all those “historic markers” that most people blow past as they go haphazardly barreling through their lives and down the road.  Driving around Miyakojima, a Ryukyu island in the Okinawa Prefecture of Japan, Jody and I passed just such a monument.  Of course we stopped, and found a more remote but significant trace of war in jungled-covered coral mounds of the Far East.

Roadside Historic Marker

Roadside Historic Marker

After their defeats of 1943, Japan knew they were losing the war.  Looking to the hurried and desperate defense of their homeland, and in attempts to slow the steady but American advance, in March of 1944, Japan began the Shinyo (震洋 Shin’yō, “Sea Quake”) manned Explosive Motor-Boat (EMB) program.  The first models of these kamikaze craft were copied from existing Japanese 18-meter motor torpedo boats, themselves copies of American hulls from the late 1930s.  Initially built of steel and constructed at Yokosuka Naval Base, wood was ultimately selected because of availability of materials.  These boats were just one component of the wider Japanese “Special Attack Units: program which incorporated aircraft, divers, boats and torpedoes in suicide attacks.  Nothing much “special” about that.

Shinyo Suicide Boats

Shinyo Suicide Boats

In August of 1944, the first 400 future boat captains started training near Yokosuka.  The students, all would-be aircraft pilots with an average age of 17, were diverted from flight schools because of the lack of aircraft production throughout Japan, given the strangling American maritime blockade of that island-nation and the ongoing strategic fire-bombing campaign of their cities and industrial centers.

Braving the Banana Spiders at the Tunnel Entrance

Braving the Banana Spiders at the Tunnel Entrance

Initially there was a planned 3-month training period focusing on small-boat handling, mechanics and attack techniques, but the pressing needs to defend the Philippines, Okinawa, Formosa and Hainan Island required hasty deployments starting almost immediately.  In September 1944, the first Shinyo Squadrons were sent to the Bonin and Haha (islands about 600 miles south of Tokyo), and the Philippines.

Tunnel Entrance

Tunnel Entrance

The 41st Shinyo Squadron with 55 authorized EMBs and a compliment of over 100 men were deployed to Miyakojima in March 1945.  On this island, roughly halfway between Okinawa and Taiwan, the Japanese Imperial Navy 313 Construction Unit dug numerous tunnels to hide the unit’s Model 1 Shinyo EMBs at Karimata Inlet and various other locations.  The Squadron was there to defend the island from expected invasion because of the active airfields found there, but invasion never came.  The squadron never had a chance to engage in battle.

Shinyo Type 5

Shinyo Type 5

Type 1, one-man Shinyo EMBs were relatively slow and only capable of speeds up to about 18 knots when fully armed.  Typically, Navy EMBs were equipped with a bow-mounted explosive charge of 500-600 pounds that could either be fired by contact fuse (when ramming an enemy vessel), or manually from the craft’s cockpit.  Army EMBs carried depth charges at the stern and were not considered “true” suicide boats as the pilot was supposed to drop the depth charges, setting off a timed fuse, and run.  Very few pilots survived, however, given there was only 6-seconds to escape from an ensuing massive explosion.  Some boats were armed with anti-personnel rockets to help neutralize surface fires from the ships being attacked.

Type 1 and 5 Suicide Boats

Type 1 and 5 Suicide Boats

The slightly larger and faster two-man Type 5 Shinyo EMBs were powered by two Toyota 6-cylinder automobile engines, armed with a 13.2mm heavy machine gun (roughly equivalent to our 50 cal), and were designed to serve as command & control boats being equipped with radio.

Tunnel Interior Today

Tunnel Interior Today

Over 6,100 Shinyo EMBs were manufactured for the Imperial Japanese Navy, and roughly 3,000 somewhat similar Maru-ni EMBs were built for the Imperial Japanese Army.  Around 1,100 boats were transported to the Philippines, 400 to Okinawa and Formosa (modern-day Taiwan), and smaller numbers to Korea, Shanghai, Hong Kong, Hainan and Singapore.  The vast majority – some remaining 7,000 kamikaze boats – were stored along the shores of coastal Japan for defense against the expected invasion of the Home Islands.  The Naval General Staff expected a 10% success rate, or roughly ~900 successful attacks for the suicide boats.  This was not the case.

emb

EMBs scored very limited successes in the Philippines and Okinawa.  Heavy gunfire from Allied ships and PT-boats (patrol boats referred to as “fly-catchers”), along with relentless attack from the air given allied air supremacy stopped most of boats before they could even be utilized.  In the Philippines in 1944, six smaller landing and patrol craft were sunk, while a few others were damaged.  In the 88 day campaign for Okinawa in 1945, about 700 suicide boats, supported by about 7,000 personnel, were employed against the Americans, sinking only two ships and damaging the same in massive waste of the youth of a country;.  Luckily the boats at Miyakojima were never employed, although many kamikaze pilots flying from that island’s airfields suffered the ultimate sacrifice.

Tunnel Exit Today

Tunnel Exit Today

On Miyakojima, a monument to the 41st Shinyo Special Attack Squadron was erected in 2006.  Plaques there in multiple languages (Japanese, English, Chinese, and German) explain the site’s significance, and the unit’s historic tunnels can be accessed immediately behind the monument.  Three entrances/exits can be found, all connected far inside the complex (~300m), but upon exploration, no other artifacts can be found in this far-flung trace of war, except for welcoming light at the end of the tunnel.

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