The was a large underground bunker complex built during the Second World War in the town of Matsushiro, which is now a suburb of Nagano, Japan. The facility was constructed so that the central organs of the government of the Empire of Japan could be transferred there in the event of an Allied invasion. In its construction, three mountains that were symbolic of the Matsushiro municipality were damaged. Parts of the caves are open to the public today, and are operated as a tourist attraction by Nagano. Construction Construction began on November 11, 1944, and continued until Japan's surrender on August 15, 1945. Construction was 75% completed at the end of the war, with of floor-space (60,000 cubic meters (2,000,000 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. Forty-six Koreans disappeared on August 15, 1945, when Japan surrendered. The project cost ¥200,000,000. Composition 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, the Japan Broadcasting Corporation (NHK) and central telephone facilities under Mount Zōzan; the residences of the imperial family under Mount Minakami, and the Imperial Sanctuary under Mount Kōbō. Purpose 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. 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. It has been suggested that he refused because going to Matsushiro would have isolated the Emperor and allowed the army to rule in his name, effectively guaranteeing they would pursue the war to "suicidal extremes". Before the war, the Imperial Army's prevalent thinking was that Tokyo, close to the shore and on the rim of the Kantō Plain, 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