It was not the first time the castle had been destroyed. The castle was bombed during World War II. The main hall and castle square survived an April 14 attack. Four days later, it was entirely destructed.

The US military targeted the facility knowing a Japanese military headquarters lied just beneath the ground. The 32nd Japanese Army had stayed in an underground trench during the Battle of Okinawa. Shuri Castle was also bombed and destroyed in the battle.

In June of this year, camera crews were permitted to enter the area for the very first time. The ditch is about 30 meters deep and one kilometer long. A mound of dirt around 150 meters from the entrance prevented the crew from proceeding further. The 32nd army blew the area up before retreating.

Entry had been limited after the war due to the risk of collapse. Guns and helmets were found inside. Nearly 1,000 soldiers and commanders sheltered in the dim, damp trench. 91-year-old Shoken Yoza was one of them.

"I'm completely overwhelmed. I never expected to visit this place after what happened. It's my first time here since the end of the war," said Yoza.

75 years ago, Yoza stayed in the trench as a member of a child soldier group.

"There was only a dim light bulb. Water kept leaking from the ceiling. It was damp and hot. We longed to breathe the fresh air outside," he added. "Sometimes a soldier would kick us, warning us to stay spirited"

Beds and the commander's office were also inside the bunker. It also served as a fortress. Yoza would carry out soil that had fallen by bomb attacks. Going outside was the most dangerous part of the work.

Omine Naoko was another person who spent time in the ditch. Learn about the 94-year-old and others by watching the harrowing story in the video above.