At the outset of the 1967 Arab-Israeli War, the Israeli Air Force executed a masterful attack against Arab air forces, destroying approximately 400 aircraft in the first day and shattering Arab airpower capabilities.
Israel's air force demonstrated that without appropriately hardened shelters or underground hangars, fragile aircraft are easily subject to damage and destruction by blast, fragment, and fire. The Israeli strike prompted extensive base hardening efforts around the world that have continued at varying levels of effort to this day. Offensive counterair strikes against air bases typically form a key element in efforts to gain control of the air. Hardened air bases make succeeding in that job much more difficult.
Decades later, US and allied airpower capabilities are vital to deterring Chinese aggression. As part of its anti-access, area-denial strategy, China has deployed a growing and increasingly modern arsenal of ballistic missiles and advanced land-attack cruise missiles that pose a significant threat to allied airpower bases. But what has received much less attention is the significant efforts China has made to harden its air base infrastructure. By utilizing open source satellite imagery, the general public can see these important developments and the implications for the United States and its allies.
China has a long history of tunneling and underground defense fortification for strategic and military purposes. In more modern times, China pursued the Third Line Defense tunneling efforts from 1964 to 1979. They were initiated by Mao Zedong in response to concerns of an imminent US attack as US military involvement increased in the Vietnam War.
Peasant Hours of Labor
After a short break from 1966 to 1969 due to China's Cultural Revolution, tunneling efforts renewed in earnest after deteriorating Sino-Soviet relations led to border clashes in 1969. The Third Line Defense was a massive engineering undertaking, requiring millions of peasant man-hours of labor, that sought to relocate China's perceived strategically vulnerable coastal industries and cities deep into China's interior, roughly 435 miles from China's coastline and 620 miles from its western border.
As part of these efforts, China developed significant numbers of underground facilities to house its fighters and medium bombers. Many of these underground tunnels and facilities were built in the 1960s and 1970s, apparently modeled on Warsaw Pact underground shelters.
Google Earth imagery and previous work by Australian analysts reveal China today has roughly 40 underground hangars (UGH), with about 30 of them being utilized by tactical aircraft. These provide the capacity to shelter roughly 1,100 fighters and medium bombers. The current disposition of UGHs reflects the threats that Chairman Mao perceived throughout the 1960s to 1970s and before his death in 1976. Significant numbers are located deep inside China.
With the People's Liberation Army (PLA) tasked to defend nearly 14,000 miles of land border and 9,000 miles of coastline, the mostly interior position of the UGH still provide the PLA a capable defense-in-depth strategy and robust infrastructure for supporting offensive operations. An adversary would need to penetrate deep within China to hit many of the UGHs—and thus be exposed to an increasing array of integrated air defenses for an extended period. Roughly half the UGHs could only house fighters, based on the dimensions of the hangar entrances. Presumably, these would provide shelter for Chinese fighters to enable them to survive initial strikes and then contest control of Chinese airspace. Nearly half of them have entrances wide enough to house China's medium bombers. In the event of an attack, the sheltered bombers could emerge from their underground lairs to begin strikes against an aggressor.
Since 2000, however, China has embarked on a significant change in its military air base hardening strategy—the building of significant numbers of above ground hardened aircraft shelters (HAS). Distributed over 15 air bases throughout Nanjing and Guangzhou military regions in the east and southeast of China, the number of hardened shelters has grown from 92 to 312 in the past 12 years, an increase of nearly 240 percent. Some of these shelters can house more than one fighter— as much as a 250 percent increase in capacity (from 92 to 324). In essence, China has built about 20 shelters each year for the past decade.
Unlike the UGHs, most of these hardened shelters are located much closer to the coast, with many less than 345 miles from the western coast of Taiwan, enabling the PLA to quickly muster significant combat power in the region. The increase of HAS in this area is an overt gesture and warning to both Taiwan and the United States that symbolizes China's willingness to use military force as a means to enforce its unwavering claim over Taiwan.
Two well-known China scholars, Andrew Scobell at the RAND Corp. and Andrew J. Nathan at Columbia University, assert that the PLA considers a fight over Taiwan its primary war scenario as long as the Taiwan issue is unresolved. While the development of UGHs deep within China indicate an emphasis on defense, China's more recent hardening efforts point to a stronger emphasis on offensive power projection capabilities.
Why the development of hardened shelters instead of continuing with UGHs? One possible explanation is the perceived vulnerability of UGHs to precision weapons. Most of the shelters have only a few entrances, which if struck could pin aircraft inside for an extended period. In previous decades, the chances of hitting a shelter door using unguided ordnance were very low. But as the United States demonstrated in the 1991 Gulf War and subsequent conflicts, precision guided munitions delivered by a modest number of sorties have the potential to strike the limited number of UGH entrances and significantly disrupt operations.
Precision strikes against the taxiways leading to the entrances could also hinder operations. Although aircraft inside may survive, it could prove difficult to extract them from their underground lair and launch. In addition, it might be possible for the first precision guided munition to penetrate the doors with a follow-on weapon to detonate inside the UGH.
The newly perceived vulnerability of UGHs to precision weapons could thus have spurred the Chinese to build hardened shelters. Given the pace of building, the end result is a greatly increased potential number of aimpoints that must be struck to disrupt operations and destroy aircraft. Typically, hardened shelters provide protection from blast, fragment, and fire, but are vulnerable to direct hits by penetrating weapons. Chinese construction efforts have increased the number of aimpoints by nearly 130 percent from 2002 to 2014. In particular, the number of aimpoints that must be struck to disrupt Chinese combat operations near Taiwan has significantly increased. Offensive counterair efforts aimed at these PLA airfields within range of Taiwan would need to strike a much greater number of targets. The additional HAS also adds a layer of deception, making US and allied planning and targeting more difficult. With roughly 200 additional HAS spread over 15 air bases, the PLA can now disperse its squadrons more effectively to confuse targeting efforts.
US Hardening Efforts
Currently, the US military has 207 HAS dispersed among four bases in the Western Pacific, with a significant majority in South Korea. This number reflects an almost minimal increase of 2.5 percent in HAS construction over the past 12 years. The hardening infrastructure of Air Force bases in the Western Pacific was, for the most part, built in response to Cold War threats and vulnerability assessments.
Great care was given to deter and protect foremost against Soviet, North Korean, and Chinese aggression in the Western Pacific as part of a larger US effort to mitigate Soviet threats in Western Europe. In the 1970s and 1980s, USAF invested tens of billions of dollars in Western Europe to minimize theater base vulnerability from Soviet threats, but since then, investment in base hardening has proved minimal.
As numerous analysts have outlined, China has aggressively invested in deploying large numbers of ballistic and cruise missiles armed with cluster weapons as part of its larger plan to shift the military balance in the Asia-Pacific region.
Andrew F. Krepinevich, president of the Center for Strategic and Budgetary Assessments, points out that while China does not use the US term anti-access, area-denial, it does use the Chinese term
shashoujian, or "assassin's mace," which has the same meaning. Krepinevich states: "Today, shashoujian weapons and combat methods are essentially those potentially capable of deterring a superior adversary like the United States or of being employed to surprise and cripple US forces at the onset of a conflict." Analysts from CSBA report, "PRC strategists refer to shashoujian capabilities and 'combat methods' as those powerful enough to deter a superior adversary—the 'inferior defeats the superior.' " Ballistic and cruise missiles combined with modernized combat aircraft are two of the capabilities associated with the assassin's mace.
The general consensus is that should hostilities break out, China would conduct a pre-emptive strike against US and allied air bases in the region. With the advent of China's Dong Feng 26 ballistic missile, capable of reaching Guam, and the potential use of submunition warheads, anti-access challenges and air base vulnerability concerns are heightened. Kadena Air Base on Okinawa, located just 460 miles from the Taiwan Strait, houses F-15s and occasionally F-22s—and large numbers of other USAF aircraft—but possesses only 15 shelters.
Andersen Air Force Base on Guam hosts a range of strategic assets, such as B-2 stealth bombers and RQ-4 surveillance aircraft, but has no hardened shelters.
Warheads filled with submunitions could be devastating against aircraft parked in the open. In a 1999 RAND analysis, John Stillion and David T. Orletsky note that one guided ballistic missile with conventional submunitions could effect the same damage as nearly a dozen cruise missiles on an entire USAF fighter wing exposed in the open. Similarly, retired Naval War College professor Marshall Hoyler calculates China has 350 to 400 CSS-6 ballistic missiles capable of reaching Kadena that could either deliver unitary warheads to crater runways or deliver cluster munitions to destroy unsheltered aircraft on the ground.
Given the short flight times of ballistic missiles, it would be difficult to gain sufficient warning time to launch unsheltered aircraft. China could follow up with strikes by combat aircraft that could deliver significant quantities of munitions against runways, shelters, fuel depots, and maintenance facilities.
In contrast, China's air base hardening efforts would greatly increase the level of effort required to disrupt Chinese operations—instead of striking just dozens of aimpoints to pin aircraft in the UGHs, the US and its allies would need to strike hundreds. Would such a riposte be possible after absorbing the initial Chinese strikes? The potential end result could be local Chinese control of the air and the devastation of US and allied land-based airpower in the Pacific.
The United States and its allies are clearly far behind a potential adversary in their base hardening efforts. Given the threat and the new challenge illustrated by Chinese air base hardening efforts, US facilities in the Pacific Theater may need a new hardening initiative to maintain effective deterrence. Although resource allocation is always difficult, it should be noted that roughly 20 new hardened shelters can be purchased for the cost of a single fourth generation fighter.
The United States and its NATO allies made great strides in hardening their airfields in Europe during the Cold War. A similar coalition approach may be overdue to maintain deterrence in the Pacific.
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