Island Forts: Land Forces Have Value in an Air-Sea Battle

Much has been made of late of the vulnerability of U.S. Navy and Air Force assets stationed and operating in vicinity of the Chinese mainland, where in the event of armed conflict with the People’s Republic of China (PRC), they would be easily targeted and dangerously exposed to that nation’s land- and sea-based firepower. When exploring ways to mitigate that vulnerability, military planners should heed Sun Tzu’s maxim, “What is of supreme importance in war is to attack the enemy’s strategy.” To that end, the United States should consider deploying prepositioned and mobile expeditionary land forces along the first island chain and developing the maritime and aviation logistics to support such assets.¹

PRC Strategy

PRC maritime strategy is fairly straightforward: develop an overwhelming conventional first-strike and a sustainable area-denial capability in vicinity of what China considers to be its own sphere of influence. This strategy underlines two of China’s most important national policy positions: 

• China considers itself to be in an era of resurgence, regaining its economic and political position as the world’s Middle Kingdom or, more specifically, its place as the hegemonic power that determines international affairs in East and Southeast Asia. 
• As a predominantly continental power, China’s military schema is built around the concept of buffer territories or “fighting space,” to keep the devastation of a potential war on its peripheries. 

A strategy of dominance around the surrounding island chains supports both these policy positions by making potential adversary forces vulnerable to such a degree that they must withdraw from those areas.

Traditionally, the U.S. strategy has been to counter this threat with the overwhelming technical and operational sophistication of its submarines, surface ships, and land-based and sea-borne aircraft. These include U.S.-based units on rotational deployments and the forward-deployed forces assigned to the dozen or so long-term military bases in the western Pacific. While this approach has been sufficient in the past, as time goes on, it will prove increasingly unsustainable.  

As China continues to close the technological and operational leads of the U.S. military, the United States must work harder to stay ahead. The problem with technological and operational improvements, however, is that marginal increases come at increasingly prohibitive costs. At some point, the value of the naval and aviation assets in theater begins to approach or even exceed the value of the objects they are deployed to protect, making U.S. policymakers loath to employ them. The overall effect plays into Chinese maritime strategy. 

Breaking the Strategy Spiral

There are several ways the United States can alter this strategic downward spiral. The first, a longtime stalwart of U.S. defense policy, is to develop technological breakthroughs that drastically rebalance the force equation against any potential adversary. Such breakthroughs, however, take time, often are difficult to implement, and cannot be relied on as short- or even medium-term solutions.

 The second option is to increase the size of the U.S. naval presence in the region by emphasizing quantity more than quality. This has been a focus of naval thinkers for years and has manifested in various ways, ranging from the high-low mix concept of the Cold War era to certain aspects of the distributed lethality and air-sea battle models currently in practice. While there is value in optimizing U.S. naval and air forces to confront the challenge, these changes take time and are fraught with all the issues that come with changing large organizations, particularly with respect to the acquisition process. Such changes could be implemented in the near- to medium-term if the impetus for change existed, but that impetus may come too late.

The third method, and one that can be implemented rapidly with low cost and minor organizational changes, is to take advantage of China’s geographic weaknesses and recognized vulnerabilities through a strategy known as “archipelagic defense.”² Part of the reason China has put such emphasis on challenging the naval dominance of the United States in the western Pacific is that it recognizes its own inherent geographic dilemmas. 

China is precariously isolated within the island chains that surround it. From the southern tip of Korea through the Japanese islands bordering the East China Sea, down through the Philippines and Indonesia, at no point is there a stretch of water greater than 200 miles. This is problematic for China because, given the range and destructive power of modern missile systems, an adversary in control of those islands could hamper the mobility of China’s naval forces and deprive it of access to the global maritime market.

Figure 1. Possible launcher site locations.

With truck-mounted versions of the Naval Strike Missile (NSM) and Japanese Type 12 missile already having been tested during the RIMPAC 2018 exercise, the United States has access to mobile land-based antiship cruise missiles (ASCMs) that could be acquired and employed to close those gaps and deny China access to the world’s oceans.³ Continued investment in modernizing the existing High Mobility Artillery Rocket System (HIMARS) with antiship rockets or cruise missiles could provide equally effective alternatives without generating a requirement for new launching systems. As illustrated in Figure 1, 12 launcher sites located at key islands in the western Pacific and provided sufficient targeting information (from space-based assets, in-theater aircraft, or even locally operated drones) would be sufficient to close off China’s maritime access. 

With some minor modifications to technology, training, and interservice logistics, the employment of key land-based assets in the western Pacific could throw China’s strategic planning into disarray. The mobility of the launchers, when put in the hands of soldiers and Marines and paired with air-defense systems such as Hawk or Patriot batteries, would make them difficult to destroy.  Were land-based sensors also employed, they would provide valuable support in establishing the maritime air and surface pictures. The ability to contribute to the common tactical targeting picture and conduct engagements would turn even the humblest reefs into veritable “island forts.” 

Were the United States to equip allied nations to construct such a maritime barrier, Chinese military planners would face a formidable threat, which would be exacerbated by the possibility of expeditionary teams from the U.S. Army and Marine Corps with the ability to rapidly seize and reinforce dozens of additional islands in the region prior to or immediately after the commencement of hostilities. Even considering the political hurdles that would have to be cleared to put U.S. ASCMs on foreign soil, adding them to the Military Sealift Command’s arsenal would be a huge contribution toward preparedness for large-scale conflict.

By denying China surface ship and air access beyond the first island chain, these mobile island forts would force Chinese military planners to reassess their strategies for commencing hostilities in the theater. Planners would have to factor them into their calculations for how many assets they would need to conduct a successful first strike and then sustain an effective area-denial strategy. Moreover, they would have to consider acting against these mobile sites before planning any major amphibious movements to threaten U.S. allies along or outside the first island chain.  

While such a construct is worthy of investigation through high-end simulations and war gaming, analytical techniques can illustrate the value of adopting these island forts. One such analysis is to determine how much impact the ASCM batteries would have in a naval engagement that occurred within range of their positions. To do so, the Hughes salvo equations can evaluate an engagement between two U.S. guided-missile destroyers (DDGs) and six Chinese Type 022 missile boats.⁴

DDGs versus Type 022s

In this scenario, each of the two DDGs (A) has one of its SH-60 helicopters airborne, providing initial detection and the opportunity to coordinate a strike against the known hostile forces. Each SH-60 will use on-board Hellfire missiles to eliminate an enemy Type 022, and each DDG will fire four SM-6 missiles, two at each of the remaining missile boats (a₂). The U.S. targeting ability is assessed at .8 (σ_A), and the accuracy of each U.S. missile at .8 (α). 

The U.S. forces will be prepared for a counterattack, with each DDG capable of shooting down four enemy missiles before they can do damage (a₃). Enemy missiles are highly lethal, however, and U.S. DDGs are lightly armored, so each DDG will be knocked out of the fight should it suffer a single hit (a₁). U.S. forces are considered well trained and prepared for the engagement (τ_A).

For the Chinese forces, the four missile boats that survive the initial SH-60 attack (B) have eight missiles apiece (b₂), and they will have time to fire all of them before the SM-6 missiles arrive. Because they are caught off guard and have inferior targeting technologies, Chinese targeting ability will be assessed at .5 (σ_β), but their missiles are equally as accurate as the U.S. ones (β). The Type 022s have no defensive capability (b₃), but the U.S. missiles are relatively small, and it takes two to mission kill a Type 022 (b₁). The Chinese crews are deemed equally well trained and prepared for battle as the U.S. forces (τ_β).

Applying the Hughes equations for modern missile engagements produces the following results:

 ΔA = (σ_βαb₂B - τ_Aa₃A) / a₁ = 4.8 Out of Action

ΔB = (σ_Aβa₂A - τ_βb₃B) / b₁ = 2.56 Out of Action

This indicates that following the initial missile salvos, enough Chinese missiles will have landed to put four to five U.S. ships out of action, more than sufficient for a decisive result. Meanwhile, U.S. missiles will have delivered only enough firepower to put two Chinese Type 022s out of action, suggesting that the Chinese survive the initial engagement with force to spare.

Presuming U.S. forces are conducting a defensive engagement within range of the ASCMs on one of their island forts, however, creates quite a different result. 

Assuming the two ASCM launchers on the island each is able to fire two missiles at a Type 022, at a minimum the U.S. striking capacity doubles to a₂ = 8 instead of 4 and the battle becomes a draw: U.S. and Chinese naval forces both are destroyed but the island fort still is fully functioning. In the event one of the ASCM batteries is targeted by the Chinese force, the results tilt even further in favor of the United States, with U.S. forces delivering enough firepower to put eight or nine enemy ships out of action while taking only enough fire to put one or two of their own assets out of action, possibly even just the shore-based missile batteries. 

Played out to their optimal utility, the island forts would be able to fire effectively on the PLAN Type 022s before those ships were able to gain an effective firing solution on the U.S. DDGs. Under such circumstances, the island forts would, with a single salvo of four missiles, reduce the PLAN numbers from six to four ships. Should a surface-to-surface engagement then take place, wherein the SH-60 assault knocks out two more Type 022s and the remaining pair of Type 022s exchanged salvos with the DDGs, the results would be wildly favorable for the U.S. forces, which would have enough defensive power to intercept inbound missiles and enough offensive power to eliminate both remaining Type 022s.

These tactical vignettes represent possible outcomes from one scenario, but the model can be applied to countless other engagements. In any engagement, the salvo equations are helpful in assessing the value of the existing or prospective assets that may be involved. Scenarios may be designed to preclude the use of the island fortifications, but having included the increased lethality of shore-based ASCMs in their calculations, theater commanders would be hard-pressed to justify not adapting their operational plans to make best use of them. 

More important, Chinese planners will be likely to employ similar analytical methods in determining what courses of action they may take in the event of hostilities. They will recognize the strategic and tactical threats island forts present, thereby limiting their options for initiating hostilities. Whether they attack island forts with intermediate-range ballistic missiles and long-range cruise missiles or use sizable naval and aviation detachments to eliminate them in detail, they would be drawing from resources they would otherwise prefer to focus on higher end threats such as the surface, subsurface, and aviation threats posed by the U.S. Navy and Air Force.