Excavation required the removal of approximately 750,000 cubic meters of earth and rock using mostly manual labor.
The project was top-secret, with workers required to sign oaths of silence and forbidden from discussing the site.
The tunnels were reinforced with timber supports, many of which remain visible today, highlighting the emergency nature of the construction.
The site was never used by the Emperor, as the war ended before the planned relocation could take place.
Construction work resulted in a significant number of deaths among the forced laborers due to malnutrition, illness, and accidents.
The complex includes vast, cavernous spaces designed to house government ministries, communication centers, and living quarters.
The mountain terrain was selected for its geological stability and ease of tunneling into granite and tuff layers.
Following the surrender, the Japanese government initially attempted to destroy or seal many of the records related to the facility's construction.
The Matsushiro Underground Imperial Headquarters consists of a massive, unfinished tunnel complex excavated into three mountains—Maizuru, Zōzan, and Minakami—during the final months of World War II. Built between 1944 and 1945, the site was intended to serve as a secure relocation facility for the Emperor, the Imperial General Headquarters, and government offices in the event of an Allied invasion of the Japanese mainland. Labor for the construction was primarily forced, involving thousands of Korean laborers and Japanese conscripts who worked under brutal conditions. The tunnels span approximately 10 kilometers in total length, though only a small portion is currently accessible to the public. The site serves as a poignant reminder of the late-war emergency measures and the human cost associated with the project. It remains an essential site for understanding the history of the Pacific War in the Japanese home islands.
The main tunnel entrance provides the best perspective of the scale and architectural profile of the excavation.
Bring a light jacket, as the tunnel temperature remains cool and damp regardless of the season.
Wear comfortable, sturdy walking shoes to navigate the slightly uneven gravel and paved floor surfaces.
Allow extra time to read the informational placards that detail the historical context of the forced labor involved.
Do not attempt to enter restricted or unlit tunnel sections, as they are structurally unstable and blocked for safety reasons.
Closed during the winter season; generally remains accessible throughout the rest of the year.
Maintain a quiet and respectful demeanor throughout the tunnels, as it is considered a site of historical mourning.
