Thirty meters below Keio University’s Hiyoshi campus on the outskirts of Yokohama’s Kohoku Ward lies a major site of World War II history: the Hiyoshidai Tunnels (Hiyoshidai Chikago), from where the Imperial Japanese Navy commanded some of their final and most destructive battles.
The 5-km-long tunnel complex survived three air raids and has weathered nearly 70 years since the end of the war.
But some now feel that not enough is being done to preserve the site, and fear that the significance of the tunnels and their history are being forgotten. When sections of the tunnels were destroyed in a development project this spring, these worries would appear to have been proven warranted.
The Hiyoshidai Tunnels were built near the end of the war, in September 1944, after the navy leased the Hiyoshi campus from Keio earlier that year.
By that point in the conflict, the situation was looking dire for Japan: University students, including more than 3,000 from Keio, had been drafted for military service, and the navy had lost most of its fleet and could no longer command the war from the sea.
These developments set the stage for the Command Division of the navy’s combined fleet, which directed naval war strategy for the entire Pacific, to make the move to Hiyoshidai.
The navy picked Hiyoshi because it was close to the Imperial Headquarters in Tokyo and the naval base at Yokosuka.
The hilly site was also ideal for building tunnels to avoid impending Allied air raids.
After the Allies took the strategic island of Saipan in July 1944, putting all of Honshu in range for bombing raids, the navy moved its Hiyoshi base underground. By the time Allied raids hit Hiyoshi in April and May 1945, the navy’s elite were safe under the earth behind 40 cm of concrete.
Despite Japan’s grim prospects, the navy pressed on with the war. From their command center at Hiyoshi, the top brass directed some of the conflict’s most deadly and destructive battles, including the Battle of Leyte Gulf in October 1944, the Battle of Iwo Jima in February and March 1945 and the Battle of Okinawa in April through June 1945.
Moreover, from their subterranean post, the navy leadership issued commands sending scores of young men and boys, including some former Keio Hiyoshi campus students, to die as kamikaze pilots as they prepared for the “final battle for the mainland” (hondo kessen).
Yet despite their major role in WWII, the Hiyoshidai Tunnels fell largely into ruin following Japan’s defeat.
When a group of Keio researchers finally conducted a survey of the tunnels in 1985, they found that many sections were deteriorating or had been partly flooded with muddy water.
The poor condition of the tunnels led some concerned citizens and scholars to form the Association to Preserve the Hiyoshidai Tunnels (APHT) in 1989.
A group booklet explains: “More than half a century after the end of the Asia-Pacific War, the method for passing on memories of that tragic conflict is moving from people to things. If living testaments to history such as war remnants and other resources are lost, we will also lose an important indicator of how to create a peaceful society and future.”
Since 2003, the group has sought to pass on this message through guided tours of the tunnels. In a typical year, they lead around 50 tours and welcome 3,000 visitors.
But the group still worries that not enough is being done to preserve the Hiyoshidai Tunnels.
One target of criticism has been Keio University, which owns most of the land over the tunnels.
“Keio has yet to build a museum or resource center that would offer information about the tunnels,” APHT president Akira Onishi says. “The tunnels and that part of war history are hardly taught in classes at the school. Although some students may know of their existence, few know that they are remnants from World War II.”
But the APHT is even more concerned about the sections of tunnel that lie outside Keio’s jurisdiction.
As recently as April and May of this year, for example, a tunnel entrance on private land near the southeastern slope of the Hiyoshi campus was leveled and paved over with a concrete reinforcement wall in preparation for housing development.
Onishi says he was “struck with a great sense of powerlessness and regret” when he learned of the damage.
He and the APHT believe Yokohama city deserves much of the blame for the loss of the tunnel section.
“It is the administration’s responsibility to preserve cultural assets that are on privately owned land,” its website states. “The Yokohama Board of Education directly administers the tunnels in this area and knew there was an entrance [within the planned construction site], yet it failed to conduct a survey. By shirking its duty to preserve the tunnels . . . the city has invited this current situation.”
The city seemed to confirm this when officials stated in a 2013 document that local authorities “were unable to fully complete negotiations with the builder before construction began.”
However, Hideaki Ishida, chief of Yokohama’s Lifelong Learning and Cultural Properties Division, explained that the city is now taking action, saying that it is “discussing the possibility of designating the Hiyoshidai Tunnels as an ‘area containing buried cultural properties’ (maizō bunkazai hōzōchi).”
According to city documents, this designation would “require potential builders to submit prior notice of intent, thus making it possible [for the city] to issue directives requiring protection and preservation.”
Yet, Ishida conceded, “It will still be difficult to tell companies not to build there, because it’s private land.”
At the same time, the developer, Yokohama-based Chuo Kogyo, seemed to confirm that city actions thus far have largely been ineffective.
“We didn’t know anything about the tunnels before we started developing there,” said the company’s Noritsugu Ueno. “There was no prior contact from the city either.”
According to Ueno, it wasn’t until after his company came across the tunnels during digging that the city mentioned conducting a survey of the site.
But Ueno also said that “the city still hasn’t told me anything about the history behind the tunnels, or the results of its survey.”
In this context, the APHT continues to be skeptical. “It is doubtful that the central government, prefecture or city is making any attempts to protect these important cultural properties,” its website states.
Still, the group has continued pressing for support from local and national authorities. In one recent petition, the organization reiterated its view about the tunnel’s value: Because “there are fewer and fewer survivors who can directly relate their experiences, the role of passing on the realities of the war is falling on war remnants.”
The APHT petition also urged the central government’s Agency for Cultural Affairs to act.
As its website explains, the Agency for Cultural Affairs “selects, designates, and registers important cultural properties, and prioritizes their level of protection.”
Previously, the government agency noted that “the current state of historic remains from the modern era [including WWII] is not well understood,” and that “many historic sites have already been lost.”
With this in mind, the central government began conducting surveys in 1997 as the first step toward protecting such sites.
According to Shigeo Otsuka from the agency’s Monuments and Sites Division, around 800 WWII-related sites have been investigated thus far, and these have been ranked A, B or C based on their level of national historical importance.
Otsuka also confirmed that the Hiyoshidai Tunnels were included in the government survey, and were given the highest-level A rank, meaning they constitute “a historic site essential to the understanding of our modern national history.”
Although the results of that part of the survey were scheduled for completion in 2004, Otsuka says that they have yet to be released.
The agency’s website offers one possible reason for withholding the results of the survey: “There are various opposing viewpoints about the significance of events in modern history, and therefore it is difficult to gain national consensus on protecting such sites.”
But some APHT members see something more sinister behind the apparent lack of interest within local and central government for protecting sites such as the Hiyoshidai Tunnels.
“It’s because they tell of Japan’s role as an aggressor in the war,” said one, Yuzuru Yamada. “From these tunnels, leaders sent people to their deaths.”
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