"I remember..." Zhao Yu was driving carefully while he spoke. "In Yuan Juncheng's work logs, there was a description of Yishan Fortress. During the period of the Manchukuo government, Yishan Fortress was always regarded as the gateway to the whole Feng Ping area. Yuan Juncheng had once suspected that there were other supporting fortifications on the front of Yishan Fortress. So, he did research in this area but found nothing."
"Front? But..." Cui Lizhu looked at the map displayed on the phone and said, "we are now at the back of Yishan Fortress, not the front..."
"Yes," Zhao Yu said. "The back of Yishan Fortress is all cliffs. It was not a strategic area during the war. So, neither Yuan Juncheng's team nor the other experts had conducted any large-scale searches here. But..."