[To the] State Council and the Central Military Commission:
During the journalism delegation’s visit to [North] Korea, the [North] Korean side arranged for the delegation to view some [of North Korea’s] war preparations. We will describe some of the situation as we understood it:
- We saw three war preparation projects. The first is an underground machine tool plant. The cave has three tunnels with heavy machinery and power generators, and each tunnel is 600 meters long. The total area of the cave is 30,000 square meters. Construction began near the end of the Korean Liberation War, and the facility has been in use for nearly twenty years. The workers there are in good health. The second [project we saw] is an underground textile factory. The area of the facility is 20,000 square meters and was also built during the initial period of the [Korean] War. The facility has been in production, and the workers there are also in good health. The third is [deleted].
- Since the armistice, the [North] Korean side has emphasized war readiness in its national defense and economic development. They attached importance to underground construction [projects] and have obtained some experience [in this regard]. From our many conversations, we feel that:
- They are very attentive towards the selection of locations and expend great efforts on surveying locations. The underground machine tool plant and the underground textile factory which we visited were both built in locations selected by the relevant departments, and construction at these facilities only started after Comrade Kim Il Sung himself personally paid a visit. They said that the key is not how tall the mountains are, but how solid the rocks are.
- While picking locations, [the North Koreans] factored in both peacetime and wartime considerations. Their locations are favorable for wartime concealment but are also useful for peacetime production. Generally, they pick locations which are not too far from transportation lines. They said that if a mountain is 70 to 100 meters tall, then it can defend against nuclear weapons, but if the enemy discovers the site, then nothing can be done. Currently they have a railway branch line connecting the underground machine tool plant and the underground textile factory to the main railway line. In order to conceal the underground factories, some additional workshops were built outside of both factories.
- Based on these projects, it seems that they have resolved the issue of moisture and dampness. When we entered the caves we did not see any signs of leaks as it is relatively dry inside of the caves. [Even] the machines that have been in the caves for many years now did not show any signs of rust. According to the introduction provided by the [North] Korean comrades, they had initially encountered [water] leaks and dampness during tunneling and construction, [but] resolved the problem through: 1) For the larger leaks, they installed pipes to lead the water out and use the water for daily and industrial purposes. 2) They have sealed the smaller leaks by using the grouting method. 3) As for dampness, they installed air conditioning equipment in the caves which can adjust for cold and warmth; the air inside of the caves was kept dry and fresh. Having resolved moisture issues and with the presence of air conditioning and appropriate shifts for workers, the health of the workers in these two factories is excellent. Despite spending long periods of time working in the caves, it is very rare [for workers there] to suffer from diseases which are common to living in caves for long periods of time.
[North] Korea is constantly expanding underground construction because of wartime necessity, low costs, and the advantages [that caves] are warm during the winter and cool during the summer.
Chinese Journalism Delegation in [North] Korea
21 July 1971