Evidence suggesting that thousands of underground tunnels and bunkers have been built in Myanmar using North Korean engineers and engineering know-how has recently been published by a number of organizations, including Daily NK. Thereafter, the scale and sophistication of North Korean tunneling capabilities has become something of an international point of interest.

So, what is the standard of North Korean subterranean construction technology? Certainly, North Korea’s construction experience is broad, and building an underground tunnel complex in Myanmar does not represent an engineering challenge of any great moment.

What is well-known is that North Korea, in the 1960s, began digging countless underground tunnels beneath the demilitarized zone (DMZ) in preparation for a possible invasion of the South, and thereafter for many other purposes besides.

The first such invasion route (the so-called first Infiltration Tunnel) was discovered beneath the DMZ on November 15, 1974, and three more have been discovered since then. It is suspected that many more may exist, but they are unlikely to be counter-tunneled due to the expense of so-doing. One of the four, the 3rd is a major tourist attraction for visitors to the South. These tunnels were built for swiftly transferring reinforcements and firepower south in the event of war, and many thousands of armed soldiers could move through them each hour.

The North developed a fixation on the more general application of subterranean infrastructure after studying the strategy of the Vietcong during the Vietnam War, and began to use tunnels thereafter to mitigate its military inferiority.

Some tunnels are used for emergency defense and to offer shelter. These have been constructed to protect civilians and soldiers. Others are to produce military goods underground in preparation for nuclear, missile and air attacks in a modern war.

The most famous of these underground shelters, which was built in preparation for nuclear or missile attacks, is undoubtedly the Pyongyang subway. Construction started in 1968 on the system, which was built 100~150m underground with technical support from the Soviet Union.

Furthermore, North Korea, in preparation for war with South Korea, has put all infirmaries for units dispatched to the DMZ, concealed weapons including long-range artillery pieces and modes of transportation underground. Recently, it has been suggested that other facilities, including support facilities, storage and even a runway at Wonsan Airport, and a submarine base, are being or have been built underground.

The North has also moved all its munitions factories into tunnels so as to prevent their destruction from above; among these, "Victory Automobile Factory," and "Heecheon Machine Tools," which are in charge of tank and automobile production, are well-known.

In particular, around Kangye, in the area of Jangang Province where there is a major concentration of munitions factories, the surrounding mountains are riddled with underground tunnels five to six-levels deep, which are known to contain large conference rooms and even basketball courts.

Who does all this tunneling? Tunnel engineering is led by People's Army Bureau No. 7, which constructs military as well as clandestine facilities for the People's Army (KPA). Missile bases and the Pyongyang subway were all built by this engineering unit.

In addition, since 1985, North Korea has had "No. 50 Construction Office," which builds subterranean civilian command facilities on the orders of each municipal and county People's Committee.

The civilian command is a complex of underground offices to which Party and administrative offices can retreat in times of emergency. In addition, the Construction Office builds underground facilities to preserve so-called No.4 (medical products, oil and clothing), and No.2 commodities (food).

Normally, Construction Office No. 50 consists of 150~200 people in each city and 50~70 people in the counties.

Evidence suggests that the North is continuing to build tunnels for various purposes to this day.