However, Japan’s basic exploration work was carried out with utmost rigor. When the Soviet Red Army attacked the Kwantung Army, our underground operatives tried to locate these documents, but failed. Afterwards, their whereabouts became unknown: the Chinese believed they had been seized by the Soviets, the Soviets thought the Japanese had destroyed them, and the Japanese believed the Chinese and the Japanese surrendering forces had secretly reached an agreement to take them away. What none of the three sides realized was that these materials had actually been lying in the swamps of the Greater Khingan Mountains in China for a full twenty years.

These materials were invaluable. Later on, to a certain extent—especially in the exploration of several large shallow mineral deposits in Inner Mongolia—they played a very important reference role.

From these materials, we can see the meticulousness of the Japanese in their work. All the exploration data was sorted and sealed in leather boxes, with different types of information having covers of different colors. Later, these items were strictly categorized by the confidential working group at the Beijing Archives Bureau.

This was originally a very ordinary matter, but an incident occurred that made this unexpected discovery particularly special.

Because all these documents were written in Japanese and contained a large amount of geological exploration data, translators and geological surveyors had to collaborate closely, making the sorting process extremely slow. During this period, something happened: one of the Archivist, at the bottom of a leather box numbered 0-34, discovered a strange black coded metal box.

It was a very peculiar box, pressed at the bottom of the case, quite inconspicuous, but the combination lock on the box was extremely sophisticated—clearly a military-grade item at first glance.

What was inside? When the box was reported, it aroused intense interest at the highest levels. They brought in Expert for consultation, and after much effort, using chemical agents to break open the box, they finally extracted a piece of geological exploration data written in code words from this mysterious box.

At the time, they were very puzzled: why did this particular document need such special preservation? Was there something different about the area explored in this geological report compared to other places?

The central authorities suspected that this document might contain clues about the Japanese search for oil back then. However, all the key information in this document was written in cipher. The Japanese codes were extremely sophisticated and could not be deciphered at the time, and the Americans held the Japanese codebooks. Since the Korean War had ended only a few years earlier, there was no way to negotiate with the Americans to borrow them. So we had no idea about the specific contents, and could only discern the location and scope of the exploration.

Accordingly, as recorded in the materials, a special project team was formed under the already ongoing Project 723. One of the three exploration teams secretly took the document into the jungle here, searching for the clues recorded within. Sure enough, they discovered the very Japanese army temporary base where we are now.

However, the place was already deserted. Everything had been burned, not even a scrap of paper remained. Only some traces nearby allowed them to determine that a Japanese exploration team had indeed conducted a thorough survey in the area. The scope even covered 80% of the mountainous jungle here.

Yet, after our own exploration team conducted a general survey in the vicinity, they found nothing at all—nothing was visible on the surface. Even shallow digging yielded nothing. There were no geological features here worth exploring.

The Japanese’s extreme attention contrasted sharply with our own team’s complete lack of findings. At the time, the Project 723 Supervisor sensed something unusual. Trusting the Japanese exploration data and based on the depth of oil-bearing strata, the central authorities made a decision: to deploy the Soviet-imported “seismic exploration equipment” to conduct seismic surveys in this area.

This was a relatively advanced technology at the time. Here is an excerpt explaining how this equipment works:

Seismic waves are artificially generated at the surface. As they propagate underground, when they encounter boundaries between rock layers of different properties, the seismic waves are reflected and refracted. These waves are received at the surface or in wells by detectors. The received seismic signals are related to the characteristics of the seismic source, the position of the detectors, and the properties and structure of the underground rock layers the waves have passed through. By processing and interpreting the seismic records, one can infer the properties and shapes of the underground strata. Seismic exploration surpasses other geophysical methods in terms of stratification detail and survey accuracy. The depth of seismic exploration generally ranges from several dozen meters to several tens of kilometers.

China began importing this equipment in 1951, and by this time already had some practical experience operating it. This equipment was generally used for exploring ultra-deep ore deposits. Today, the feedback data from exploration is three-dimensional and extremely impressive, though for ordinary people, it still looks like a huge mess of chaotic curves.

Afterwards, through “geological data imaging” calculations, these curves could be converted into roughly readable black-and-white film. Now, our exploration already has related software that can generate this in real time, but back then, people had to use hand-cranked calculators to do the math. Of course, all this was the work of Scientist; for us basic technical soldiers, it was like listening to a foreign language. We could only understand the kind of black-and-white film produced after geological imaging.