During World War II, Japanese naval forces in Okinawa, led by Rear Admiral Minoru Ota, built an elaborate underground headquarters, with hundreds of meters of connecting tunnels under a hill in Tomagusuku. On June 4, 1945, the U.S. 6th Marines landed and a pitched battle ensued.

Ota sent his farewell telegram to the 32nd Army on June 11. In it, he commended the Okinawan people's self-sacrifice and cooperation during the battle. Ota then, along with members of his staff, committed suicide on June 13 to avoid surrender. The Marines sealed the entrances to the underground headquarters rather than attempt to enter it. When it was unsealed in the 1950s, the remains of over 2000 sailors were found.

Today, the Japanese Navy Underground Headquarters can be visited by the public. Traces of the mass suicide by Ota and his men can still be seen. Blast scars from a hand grenade are visible on the walls and the farewell message left by Ota is still clearly visible.