On a hillside overlooking an athletic field where high school students play volleyball, an inconspicuous entrance leads down a dusty, slippery slope — and seemingly back in time — to Japan’s secret Imperial Navy headquarters in the final months of World War II.

Here, leaders of Japan’s combined fleet command made plans for the fiercest battles, including those of Leyte Gulf, Iwo Jima and Okinawa from late 1944 to the war’s end in August 1945, AP reports.

The entrance of underground tunnels that Japan’s Imperial Navy once used as secret headquarters underneath of Hiyoshi Campus of Keio University
The entrance of underground tunnels that Japan’s Imperial Navy once used as secret headquarters underneath of Hiyoshi Campus of Keio University in Yokohama

They knew when kamikaze pilots crashed to their deaths when signals from their planes stopped. They cried when they monitored cables from officers aboard the famed battleship Yamato as it came under heavy U.S. fire and sank off southern Japan.

Today, the barren, concrete tunnels sit quietly underneath a high school and university campus, largely untouched and unknown, occasionally visited by guided tours for the students. The school opened them to the media for the first time this week to raise public awareness of the site and the tragic history it represents, in the 70th anniversary year of the end of World War II.

“It’s a negative heritage that humans made. It’s the perpetrators’ legacy,” said Takeshi Akuzawa, assistant headmaster of Keio Senior High School, who escorted the media tour on Tuesday. “Just imagine the massive number of people who had to die in the final year of the war because of their operations.”

The inverted U-shaped tunnels are a silent reminder of a time when students and many others were sent to war, many to their deaths, under orders that emanated from this bunker under a school.

Experts say the significance of such war remains is increasing, especially as that era fades from memory, and amid a growing reluctance among some Japanese to look at the negative side of the history.

One of the top Japanese universities, Keio, leased the site to the navy in 1944 under an Education Ministry order, after thousands of teachers, staff and students were drafted and sent to the battlefield, leaving the campus virtually empty. Above ground, the navy commanded from a dormitory, rushing to the underground command center whenever U.S. B-29 bombers flew over.

Keio’s Hiyoshi campus, south of Tokyo in Yokohama, was chosen apparently because of its relative proximity to both Yokosuka naval base and command headquarters in Tokyo. The hilltop campus also was suitable for an underground facility.

Construction of the underground tunnels began in July 1944, mobilizing troops and Korean forced laborers. A room for the chief commander, Adm. Soemu Toyota, and key departments were up and running in a few months.

Only in the chief commander’s room, cement on the walls was smoothed out, the floor was covered with tatami mats and there was a door. He climbed up and down 126 stairs between the two command centers — above and below ground. His room was slightly elevated so that the floor remained dry, and there was even a flush toilet.

The tunnel command center also had ventilation ducts, a battery room, food storage with ample stock of sake, in addition to deciphering and cable and communications departments. Marks on the ceiling remain from where overhead lights hung. The tunnels housing the command center and its facilities under the campus are 30 meters (100 feet) underground and stretch about 2.6 kilometers (1.6 miles) in length.

The conditions for those leading the war contrasted with those of ordinary people, who hid in small mud shelters as firebombs rained down from the sky, Akuzawa said.

Hisanao Oshima, who was there from February to May 1945 as a communications crew monitoring Morse code, still cannot forget the moments when he lost signals from kamikaze fighters. “The sound stops, and that means he crashed. I just cannot get that out of my head,” he said in an interview with public broadcaster NHK.

This site must be preserved “so that we can say it’s the proof why we should not wage war ever again,” Oshima said.

Japan also built the Matsushiro Imperial Underground Headquarters in central Japan for then-Emperor Hirohito and Imperial Army and key government officials, as they prepared for a possible ground war with the Americans, though that one was never used.

Hundreds of hangers, tunnels and other wartime remains still exist in Japan, but many have been abandoned as interest has waned. A growing sentiment among some conservatives favors the removal of such remains if they are seen portraying the negative history.

Sections of the navy tunnels at Keio were damaged in a development project a few years ago, prompting experts and volunteers to call for more support from the city to preserve the site.

Akuzawa said what struck him the most as a teacher was the fact that the university was used as a war command center to send students to the battlefield. A Keio University graduate himself, he did not know about the tunnels until he started teaching at the high school.

“I feel emotionally shaken when I think of those students sent to war were just like these boys,” he said.

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