INTRODUCTION
Warfare in the 21st century has been characterised by the increasing sophistication and proliferation of C4ISR assets, across land, sea, air and space, offering militaries unprecedented and persistent battlefield information. However, this has also created an increasing asymmetry, with the benefits of these enhanced capabilities going to forces that can afford these increasingly expensive assets while simultaneously raising the technological and financial threshold for states seeking to possess comparable systems.
It is in this context that lessons have been drawn upon from the recent conflict between Iran and the United States, that has brought into the limelight Iran’s widespread use of subterranean networks, in order to enhance the survivability of its forces in an asymmetric battlefield. Indeed, the conflict shows how subterranean warfare, once restricted to tactical applications such as bypassing enemy defences, has now become a tool at the strategic level, through Iran moving strategic assets such as its nuclear infrastructure, missiles and even entire bases underground. Thus, this article aims to explore how the Chinese People’s Liberation Army thinks about Subterranean warfare, and the implications it could carry for any conflict with the PLA.
THE ORIGINS OF PLA SUBTERRANEAN WARFARE
The PLA’s experience with subterranean warfare dates back to the Second Sino-Japanese War (1937-1945), where the PLA initially adopted the use of tunnels in Hebei to counter Japanese superiority, which slowly evolved into a well-connected network of tunnels, underground shelters and fortifications. As the PLA sees it, this innovation allowed them to gain a first mover advantage, and by opening up a new subterranean domain in the battlefield, forced the Japanese to devote more troops and resources to achieve military objectives.
This system would be further refined during the Korean War, with the PLA instituting its first standardised construction requirements for underground tunnels and fortifications, stipulating the depth and thickness of tunnels, entry and egress points, layout of living quarters, supply depots, respiratory and life support systems, and integration of subterranean infrastructure with frontline trenches, communications trenches, anti-tank and anti-aircraft positions, and bunkers. By the end of the war, the PLA had constructed a defence-in-depth of 20-30 kilometres across the 250 km frontline. These subterranean complexes served a range of functions, such as, protection from shelling and air attack, assisting with defensive operations, acting as assembly areas for forces undertaking offensive operations, providing cover for advancing forces. They also allowed the PLA to reduce the number of troops exposed on the surface during an ongoing battle, while retaining fresh reserves underground, which could be rapidly committed in counterattacks against disorganised attacking forces.
CHINA’S CONCEPTUALISATION OF THE SUBTERRANEAN BATTLEFIELD
Existing PLA literature on subterranean warfare centres primarily around the tactical level, where it studies subterranean warfare in conjunction with Urban Warfare. Cities, due to their concentration of resources, are viewed as centres of gravity by the PLA. In addition, the increasing scale of urbanisation around the world, with an estimated 6.3 billion people living in Urban areas by 2050, means that control of cities is essential in the PLA’s conceptualisation of warfare. It is in this context that PLA writings on urban warfare have highlighted the role of subterranean warfare as a part of controlling cities.
PLA writings cite examples such as the use of the Sarajevo Tunnel by Bosnian forces, to bypass Serb positions and reach the UN-held Sarajevo Airport, examples from the war in Syria, and most notably, the Battle of Mosul, where the complex network of underground tunnels, combined with the urban environment, forced the Iraqi Army to commit troops of a 13:1 ratio in order to retake the city. Even in this case, PLA analysts rated the underground networks used by the militants as fairly rudimentary, and not nearly comparable to the complex underground systems found in most modern metropolitan cities.
The PLA divides subterranean infrastructure into three categories: commercial subterranean infrastructure such as underground shopping complexes, warehouses, parking lots etc, public-service subterranean infrastructure, such as underground and undersea road and railway tunnels, sewers etc, and military subterranean infrastructure, such as underground air raid shelters, missile silos, submarine bases, armouries etc. The importance the PLA assigns to the Subterranean domain can be seen by its terming the Subterranean domain as the ‘Seventh Strategic Dimension of Warfare’, after land, sea, air, space, the electromagnetic domain and cyberspace.
PLA analysts identify certain key issues affecting the performance of its troops and equipment that need to be addressed in order to gear up for subterranean warfare. At the personnel level, these include insufficient oxygen content and the presence of toxic gases underground, alongside the lack of natural light. These, in turn, result in psychological and physiological effects such as reduced immunity, dizziness, circadian rhythm disorders, fatigue, depression and claustrophobia, induced by prolonged periods in underground environments. Equipment also faces limitations in subterranean conditions, including reduced effectiveness of optical systems, navigation systems (particularly GPS), communication systems and radios, reduced bandwidth etc. Even the employment of weapons is constrained to the use of light and portable systems, and the use of explosives is also restricted due to dangers such as the collapse of underground structures and the reactions of underground gases with explosives.
THE FUTURE DIRECTION OF PLA SUBTERRANEAN WARFARE
PLA literature on the subject suggests that the PLA’s thinking on subterranean warfare is evolving from a focus on small unit tactics centred around the Squad and Platoon level, to operations conducted at the battalion and even brigade level. Subterranean operations, are no longer considered to primarily be the realm of Special Operations Forces, and regular units are being increasingly trained to undertake these operations.
The PLA has also closely followed the US Army’s developments in the field of subterranean warfare, in training, doctrine and equipment. PLA literature clearly notes the US Army training 26 of its 31 Brigade Combat Teams to conduct subterranean operations, alongside issuing new equipment such as respirators and smart radios to enhance its subterranean capabilities. In addition, with the development of ground-penetrating and bunker busting munitions, alongside improved communication and navigation systems, the PLA envisions Subterranean operations to become a common part of future warfare.
As such, PLA analysts emphasise the importance of a multi-domain approach to the doctrinal development of, and execution of subterranean operations, with cooperation between various branches infantry, artillery, sappers, communications, ‘chemical defence’ (NBC) and electronic warfare, alongside the integration of unmanned and autonomous systems owing to the high-risk nature of such operations. There have also been calls for the integration of AI and other technologies to simulate subterranean warfare and improve the training of its troops for such operations.
CONCLUSION
The current body of PLA literature shows a focus on the tactical level, while the discourse with regard to subterranean infrastructure at the strategic level is extremely limited. While mentions are made of strategic subterranean infrastructure, these are mostly with regards to their ability to act as air raid shelters and associated functions. While China does possess some strategic subterranean assets, these are mostly restricted to the PLA Rocket Force and its ‘Underground Great Wall’. However, the recent conflict in Iran, with Iran’s positioning of strategic assets such as nuclear reactors and bases in subterranean structures, has given rise similar interest in Chinese circles.
One such example is an article by Zhang Shishu, chief technical expert at PowerChina, where he calls for the development of Subterranean facilities in China’s mountainous Northwest and Southwest regions, to store critical reserves of oil, natural gas and rare earth metals. The construction of such facilities will require significant time and effort, but nevertheless, should such constructions even be detected in the first place, it is unlikely that any action can be taken to prevent such construction, or attack said facilities once they have been constructed. Similarly, the PLA is constructing a new Headquarters west of Beijing, with deep underground bunkers and tunnels, aimed to protecting its Strategic Leadership and Command and Control systems in the event of a conflict.
These developments naturally affect forces that are likely to face conflict with the PLA. The most notable manifestation of the PLA’s subterranean doctrine would be if it chooses to invade Taiwan, with its range of both civil and military subterranean infrastructure, such as Taipei’s underground metro, which can also be used for military purposes, and its use of subterranean aircraft hangar complexes and an underground tri-service command centre, all carved into Taiwan’s rocky terrain, which the PLA would have to contend with in the event they invade Taiwan. Similarly, any conflict in the Pacific islands, could see all sides making use of and upgrading the remnants of Japanese subterranean fortifications on these islands from the Second World War.
Similarly, India’s mountainous borders with China are also a suitable location for the development of subterranean structures on both sides, and subterranean warfare could become a key component of any conflict on this border. As such, technical efforts need to be made in the field of countering autonomous systems, development of ground-penetrating ISR and munitions, alongside innovation in doctrine and training. Thus, there needs to be a concerted effort to closely follow unfolding events in the subterranean realm, and institute studies to develop methods to leverage the strengths of the subterranean domain and counter its weaknesses at the Tactical, Operational and Strategic Levels.
