China's Underground Great Wall: Subterranean Ballistic Missiles

Recent concerns about the size of China’s nuclear arsenal have arisen in the wake of a study by Georgetown Prof. Phillip Karber, which considers the question of why China has a vast network of underground tunnels referred to as China’s “underground  Great Wall.” Karber suggests that these 3,000 miles of complicated tunnels could host about 3,000 nuclear weapons. My recent paper (“ The defensive nature of China’s underground great wall,” Bulletin of the Atomic Scientists, Jan.16, 2012 ) provides a comprehensive response to Karber’s report — and offers an alternative explanation.

Here I want to consider: What are the purposes of this 3,000-mile network of underground tunnels?

The key argument Karber makes to support his estimate of 3000 weapons is that “more tunnel growth” means more “nuclear warhead growth.”  If those tunnels are just used for storage of  nuclear warheads, this logic might seem reasonable. However, China’s underground Great Wall is not just for weapons storage. It is operated mainly as a missile launch base (zhendi). I like to call it “subterranean ballistic missile” (an underground-based version of a nuclear missile submarine, or SSBN). Just as a submarine deterrent offers survivability, so too does a subterranean force; the philosophy underpinning the two are the same.

China’s underground Great Wall is converting  its land-based ballistic missiles into “tunnel-launched ballistic missiles” (I prefer the new acronym “TLBM”). Thus,  China has moved its land-base missiles to underground-basing to ensure a limited and reliable second-strike nuclear force after absorbing a first nuclear strike. On this basis, it should be not difficult to understand why China builds it with so many tunnels. It is the same reason a ballistic-missile submarine with about one hundred warheads needs so huge an ocean!

Given the fact that China has no reliable operational air-based (bomber) or sea-based (SSBN) nuclear forces, the main focus of the Second Artillery since 1980, when it initiated China’s nuclear modernization, has been how to ensure that its limited land-based  strategic missiles can survive a first nuclear strike. With the development of Soviet/Russian and U.S. satellite surveillance capabilities and the increased accuracy of their nuclear weapons, China became concerned about the vulnerability of its land-based missiles, in particular its silo-based DF-5s and its cave-based DF-4 missiles, which need to be pulled out and launched from pre-prepared above-ground launch sites. These liquid-fueled missiles usually take up to two hours pof reparation  for launch. In addition, unlike the US and Russia, China does not have a reliable early warning system and its missiles are not in a launch-on-warning posture.

Under its announced no-first-use doctrine, the Chinese government says it would launch a retaliatory nuclear attack only after it survived a first nuclear strike. To assure the survival of an adequate number of weapons for retaliation, China has just two primary options: One is to build more warheads and launchers, but to survive a US preemptive attack that could involve as many as a thousand warheads and extremely accurate targeting, so China would need a huge nuclear arsenal. In practice, China has chosen the second option, moving its small land-based missile force underground.

It is reported that the engineering unit of the Second Artillery began to construct the underground Great Wall in 1985 and finished it after ten years’ effort. Thus, by the mid-1990s, China had a true, reliable second-strike capability.  These tunnels have been built hundreds of meters underground, in deep mountain  areas, and are difficult to detect from space. They can withstand nuclear and conventional  attacks. The missiles, personnel and related equipment can be transported by rails and trucks within the network of tunnels  to various locations. All the activities for launch preparation can be done in the tunnels without detection. Some of the tunnels could also be for logistical support or command and control facilities.

While the road-mobile solid-fueled missiles (e.g. DF-31 and DF -31A) deployed around 2006 have significantly enhanced survivability relative to fix-based and silo-based missiles,  the US is pursuing the capability of  long-range precise conventional strike, and its space monitoring capacity to track mobile targets could make Chinese road-mobile missiles vulnerable again.

The fact that Beijing is willing to reveal the existence of the underground Great Wall shows Beijing wants potential adversaries to know it has real and reliable retaliatory counterattack capability and thus discourage thoughts of first strike. From a Chinese perspective, China’s underground Great Wall further consolidates the mutual deterrence between China and the US, and thereby enhances strategic stability.

The underground great wall provides evidence for Beijing’s minimum deterrence posture, in addition to the fact that China has a small arsenal that is deeply de-alerted and has pledged no-first-use. Unlike the US focus on counterforce targeting policy, which needs a large arsenal to get rid of the adversary’s nuclear force, China has a retaliatory countervalue posture for which China believes a small force is enough.

In practice, while China has made great economic development and technological progress since its economic reform and openness beginning in 1978, Beijing still maintains its minimal deterrence policy. No Chinese believes China would ever use its few tens of ICBMs for a first strike on a US that has thousands warheads. This is just like “using a chicken egg  against a huge stone.”

In the past, China’s minimal deterrence policy has been shown to be effective and smart, and has saved China lots of resourcse for its economic development. It is unthinkable for China to change it and to pursue parity in terms of weapon numbers with the superpowers.

If China feels confident that its underground Great Wall would ensure the survival of a reliable retaliatory force from the first strike, then the major drivers for speeding up China’s nuclear modernization would be the US missile defense, which could neutralize the surviving small force.

To respond to missile defense, Beijing could take the option to build more warheads. To discourage Beijing from moving to such a buildup, Washington should accept mutual deterrence with Beijing instead of pursuing nuclear primacy, and limit its missile defense in a way that does not threaten the potential effectiveness of China’s small arsenal. Meanwhile, if Washington and Moscow move forward to a deeper cut of their nuclear forces, China will have to reassure both capitals that it will cap its arsenal at a low level (say 200 warheads).

I recall that in a Chinese TV drama series, some soldiers died during the construction of the underground Great Wall tunnels. I believe they hoped that the underground Great Wall could prevent a nuclear war and help us to move forward to a world free of nuclear weapons. I hope that when future generations visit Beijing, they will be able to tour not only the Great Wall above ground but also the one underground.