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Coordinates: 36°32′45″N 138°12′14″E / 36.545811°N 138.203931°E / 36.545811; 138.203931

The entrance to the complex

The Matsushiro Underground Imperial Headquarters (松代大本営跡 Matsushiro Daihon'ei Ato?, lit. Matsushiro Imperial Headquarters Site) was a large underground bunker complex built during the Second World War in the Matsushiro suburb of Nagano, Japan.[1] The facility was constructed so that the central organs of government of Imperial Japan could be transferred there. In its construction, three mountains, symbolic of Matsushiro Municipality were damaged. Parts of the caves are open to the public today, and are operated as a tourist attraction by Nagano.


A view of the caves

Construction began on November 11, 1944[2] and continued until Japan's surrender on August 15, 1945. Construction was 75% completed at the end of the war, with 5,856.6 square meters (63,040 sq ft) of floor-space (59,635 cubic meters (2,106,000 cu ft) of volume) excavated. Between 7,000 and 10,000 Korean slave laborers were used to build the complex, and it is estimated that 1,500 of them died.[3] Forty-six Koreans disappeared on August 15, 1945, when Japan surrendered. The project cost ¥200,000,000.[2]


File:Matsushiro2006 1111.jpg

A diagram of the complex

The complex was an interlinked series of tunnels underneath several mountains. Facilities for the Imperial General Headquarters and palace functions were constructed under Mount Maizuru; military communications under Mount Saijo; government agencies, NHK and central telephone facilities under Mount Zōzan; the residences of the imperial family under Mount Minakami, and the Imperial Sanctuary under Mount Kobo.[4]


The original purpose of the complex was to serve as an alternative headquarters for the Imperial General headquarters. However, in March 1945, secret orders were issued to add a palace to the complex.[5] Yoshijirō Umezu informed Emperor Hirohito about construction of the complex in May, but did not tell him that it contained a palace. The plan was to relocate the Emperor to the complex in an armored train. When informed about the existence of the palace in July, Hirohito twice refused to relocate.[5] It has been suggested that he refused because going to Matsushiro would have effectively isolated the Emperor and allowed the army to rule in his name, effectively guaranteeing they would pursue the war to "suicidal extremes".[6]

The complex was designed specifically to withstand B-29 bombings.[4]

Before the war, the Imperial Army's prevalent thinking was that Tokyo, close to the shore and on the rim of the Kanto Plains was indefensible. Therefore, in the scenario of a fight on Japanese soil, they planned to have the vital organs of government shifted inland. When Saipan fell in July 1944, the bombing of Japan and the final battle in Japan became a real problem. In the same month, by a decision made at Tojo's last cabinet meeting, approval was given to transfer the palace, the army headquarters and other important governmental organs to Matsushiro.


In the initial plan, the government, NHK and the telephone bureau was planned for the Zouzan tunnel. The Minakamiyama tunnel was intended to house the Imperial Palace and the general staff. However, the soil beneath Minakamiyama could not support such a scheme and the plan was changed to shift the palace and the general staff to Mount Maizuru tunnel. On Mount Maizuru, a concrete building was constructed externally and the Minakamiyama tunnel was made into a storage facility. The combined length of the three shelters exceed 10 km. The army bought the land through government agencies. Silkworm keeping was prized then; the acquisition of mulberry fields was therefore made at three different prices according to the productivity of the lands. The land deemed useless after the war, saw its land value drop to half of the price with which it was acquired. 130 of roughly 500 families were evacuated for the construction; it was directed by the Eastern Command of the Imperial Army. Agriculture itself was allowed, so farmers and their dependents stayed at relatives' houses nearby. To conceal the extent of the evacuation, the houses of evacuated families were left as they were and the families were allowed to leave with only three tatami mats. After the war, on the 9 November, some returned to their houses and started repairs. The first explosion was made on 11 November 1944 and work commenced thereafter. Dynamite was used and the debris was removed primarily via human labour. In total, 7000 Koreans and 3000 Japanese worked three eight-hour shifts, later two twelve-hour shifts on the site. Aside from the above, another estimated 120,000 workers from Nishimatsu Company, 79,600 labour volunteers, 157,000 subcontractors from Nishimatsu and Kajima company, 254,000 Korean labourers were involved in the project. However, at 75% completion, work was halted on 15 August due to the surrender.

Imperial Shrine[]

There was in place a plan to move the Imperial Regalia of Japan of the Imperial Sanctuary from Tokyo to Matsushiro. Initially, the replacement shrine was planned in the Maizuru tunnels. However the Imperial Household Agency strongly insisted[citation needed]: "Even some unfortunate mishap should befall his Majesty, the three artefacts (of the regalia) are inviolable. We will not allow it to be stored in the same place as the residence. His majesty's residence should be built to face south, forming a straight axis as the Shrine of Ise, and that should be performed by Japanese of pure blood."

However, the unit in charge of the shrine had no idea how to build one. Tokyo University engineering professor Private First Class Sekino Katsukazu was put in charge. The headquarters asked for the advice of several other professors. At the instruction of one, the tunnels split into lightning forms, reducing the impact from the bombs. The "Japanese of pure blood" came from youths at the Atami branch of the Railroad Ministry training institutes. Work started in July 1944, but was halted shortly after.

Naval Tunnel[]

The Japanese Navy headquarters which was against a standoff on Japanese soil were nonetheless allotted a tunnel plan in June 1945. The 300th Division in Yokosuka building aircraft hangars sent half of its strength to build the naval tunnel. It was intended to be 3.5 km long and was 16 km away from the rest of the complex in Matsushiro. The capacity of the tunnel was approximately 1000 people. The group managed 100m into the ground before the surrender.

Comfort Women[]

Around the shelters, there were three comfort houses with 4 to 5 Korean comfort women servicing these. These were however not intended for soldiers, but primarily for supervisors of higher standing within the ranks of the Korean labourers. However, it is rumoured that children were chided for having stole a glance at soldiers in trucks and women in what appeared to be Chinese clothes. Among these, there was an entertainment room for female staff of a local company. After its liquidation in 1938, it became in September 1944 an accommodation facility for labourers. To prevent troubles with local women, it was used as a comfort house. In November, a Korean family of five and three comfort women who could not speak Japanese, allegedly brought in by Korean authorities to comfort Korean labourers, started a gambling facility in the premises. It is unclear if concurrently, sexual services were provided. After the war, the family and others left for home.


Major Ida Masataka of the Ministry of War of Japan and later of Kyujo Incident fame, proposed the location. After the general staff approved of it, the Railway Ministry conducted a survey of the area, finalising the plans to build such a complex. Five points were raised in Ida's proposition;

1) the widest flat area in Honshu, with an airstrip nearby;

2) solid substrate suitable for excavation and ability to withstand 10 ton bombs;

3) completely surrounded by mountains, yet having sufficient flat surface area for underground constructions; 4) abundance of labour (later proven untrue);

5) Nagano prefecture's residents are simple, making the concealment of the facility easier; the old name for Nagano, Shinshu rhymed with God's Land, and is auspicious. This proposition primarily involved setting up bunkers for the army throughout the Japanese homeland. It was afterwards, that Prime Minister Tojo Hideki expanded the project to accommodate the transfer of the government.

While the project was an operational secret in the guise of a warehouse, from the statement of a local Japanese labourer, rumours were rife in the surrounding villages and towns that the emperor was coming to town. The cause of the rumours was due to the massive amounts of cargo that came on trains.

After the war[]

1946, a local Buddhist association received permission to convert what was meant to be the imperial palace into an orphanage.

1947, plans to convert the whole complex into an orphanage complex for war orphans were debated but not materialised. 1947, the weather agency sets up a seismographic office in the concrete building at Mount Maizuru. Below, an assortment of seismographs and equipment were placed, making it the largest office of its kind in Japan. 1967, Matsushiro earthquake centre is built on part of the Maizuru ruins following a local earthquake. 1990, parts of the Zouzan bunker are opened by the Nagano Municipality, Shinshu University sets up an astronomical observatory within. Subsequently, more of the complex is opened by the sightseeing department of the same office.

After the surrender of Japan, most of the documentation relating to the Matsushiro complex was destroyed. As a result, very little is known about the day-to-day construction of the facility.[4]

The complex today is administered by Nagano city's sightseeing bureau. The caves are mostly closed to the public - only the first 500 meters of the Mount Zōzan facilities are open.[7]

The city of Nagano spent many years trying to attract the Olympic Games, culminating in their successful bid to host the 1998 Winter Olympics. During the bidding period and again during the games itself, peace activists accused the city of Nagano and the Nagano Organizing Committee (NAOC) of burying the past. Yamane Masako noted that "just the other day, the authorities blocked the entrances to the underground shelters with fences, despite requests that the last Imperial General Headquarters should be preserved and left be open to the public. They're afraid it will hurt their chances to get an Olympic Games to come to Nagano. They're trying to draw down a curtain around the Showa era. It's inexcusable." During the games, the complex was omitted from all maps and tourist information passed out to visitors. Peace activists asked the NAOC to include the caves on the list of interesting places to visit in Nagano, but their requests went unanswered.[8]

See also[]

Other bunkers:


  1. McCormack, 253
  2. 2.0 2.1 Cook, 433
  3. Cook, 436
  4. 4.0 4.1 4.2 World War II Imperial Headquarters - Matsushiro . Japan Travel Guide. The Yamasa Institute
  5. 5.0 5.1 Drea, 206
  6. Drea, 206-207
  7. Japan Visitor Blog - Matsushiro Daihonei Nagano. September 02, 2008
  8. Digging Up the Past. Sonni Efron. Los Angeles Times, February 09, 1998


  • Cook, Haruko Taya; Theodore F. Cook (1992). "Chapter 22 - Interview with Yamane Masako". Japan at War: An Oral History. New Press. ISBN 1-56584-039-9. 
  • Drea, Edward J. (2003). In the Service of the Emperor: Essays on the Imperial Japanese Army. University of Nebraska Press. ISBN 0-8032-6638-3. 
  • McCormack, Gavan (2001). The Emptiness of Japanese Affluence. M.E. Sharpe. ISBN 0-7656-0767-0. 

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