The sands are quickly shifting in the South China Sea. New reports suggest that China may be preparing to conduct land reclamation at Scarborough Shoal, which is seized from the Philippines in 2012. And just weeks ago, satellite images revealed that China had installed sophisticated radar on Cuarteron Reef in the Spratly Islands and deployed two batteries of surface-to-air missiles on Woody Island in the Paracels. Further, following its rapid-fire island building, runway construction, and efforts to assert claims to new water and airspace, many experts agree that China could soon declare an Air Defense Identification Zone (ADIZ) in the South China Sea to match the one it has already claimed in the East China Sea. This would be yet one more attempt to interfere with air traffic over the contested waters.

In many respects, however, Washington’s own efforts in the South China Sea are bearing fruit, too. The United States spotlighted China’s assertive behavior, has resumed freedom of navigation operations, and is building regional support for them. It is closer than ever with the Association of Southeast Asian Nations, and its ASEAN partners have begun to articulate serious, sustained concerns about freedom of navigation, freedom of overflight, and the rule of law in the South China Sea, which are Washington’s primary national interests.

It is something of a puzzle that Washington has simultaneously made measurable political strides while also facing defense setbacks in the contentious waterway. But the reason is simple. Washington has focused its South China Sea strategy on the political balance in the region, aiming to maximize regional support for its interests while it augments its military posture over time. Beijing, on the other hand, has been focused on the tactical military balance and has been building islands faster than the United States can build coalitions. The result is a political balance that is generally quite favorable to Washington but a military balance that is anything but.

A Philippine flag flutters from BRP Sierra Madre, a dilapidated Philippine Navy ship that has been aground since 1999 and became a Philippine military detachment on the disputed Second Thomas Shoal, part of the Spratly Islands, in the South China Sea March 29, 2014. Erik De Castro / Reuters IN THE BALANCE

Scholars, including Kenneth Waltz and Stephen Walt, have written volumes about the phenomenon of balancing in international relations, in which states band together to counteract the capabilities or threats of a prospective adversary. Balancing is presumed to be a natural tendency of the international system: when faced with a rising challenger, states with similar security interests will overcome other obstacles to pool their energies and resources to thwart the foe.

The U.S. strategy for the South China Sea is premised on a form of balancing. As policymakers often repeat, the United States is not a claimant in the South China Sea, but it does have clear interests there, including freedom of navigation, freedom of overflight, and the rule of law. In other words, it wants to protect the basic rules of the road that make up the international order in Asia. It rightly recognizes that a South China Sea strategy that alienates regional states cannot ultimately be successful in achieving these ends. It also cooperates with China on numerous issues ranging from Iran and North Korea’s nuclear weapons programs to climate change. Washington’s gambit, then, has been a robust effort to harness the power of regional balancing against China’s South China Sea assertiveness.

Over the past seven years, through the Rebalance to Asia, the United States has invested copious diplomatic energy in its relationship with ASEAN. It has upgraded and formalized its ties with the association and has provided leadership from within ASEAN on South China Sea issues. It has also invested in its bilateral ties with other countries caught up in South China Sea disputes, including Malaysia, the Philippines, and Vietnam. Many of these initiatives predate China’s most recent behavior and are part of broader efforts to demonstrate U.S. interest in an important region. But they have taken on renewed purpose as Beijing sought to expand its reach in the South China Sea.

A satellite image released by the Asian Maritime Transparency Initiative at Washington's Center for Strategic and International Studies shows construction of possible radar tower facilities in the Spratly Islands in the disputed South China Sea in this image released on February 23, 2016. Reuters And the political investments have produced some real diplomatic payoffs that would have been hard to imagine several years ago. In recent statements, ASEAN has expressed grave concern about China’s island building and the fact that it jeopardizes freedom of navigation and freedom of overflight in the region. Until very recently, the organization would have been loath to use language that risked alienating China. And despite the fact that many of its member nations retain close economic and even political ties to China, South China Sea claimant states have begun to stand up to China individually, decrying its flight tests of new runways and deployments of weapons systems. Leading analysts, such as the Council on Foreign Relations’ Joshua Kurlantzick, have noted that the United States’ diplomatic balancing act appears to be working. Southeast Asian countries are closer than ever to Washington and are increasingly fearful of Beijing’s longer-term intentions.

Washington’s strategy has surely not been limited to the diplomatic realm: closer political ties have allowed the United States to strengthen its security posture around the South China Sea. Singapore has agreed to host four U.S. combat ships and a surveillance aircraft. The United States is rotating a marines detachment through Darwin, Australia. The Philippines has approved an Enhanced Defense Cooperation Agreement, which will permit Washington access to at least five bases that abut the South China Sea. U.S. allies are also forging closer security ties among themselves; Japan and the Philippines recently signed a defense agreement.

The challenge is that the political and security elements of Washington’s coalition-building strategy are long-term efforts that require constant tending. Every state in Southeast Asia has a unique set of interests to consider, including its relationship with China. Moreover, whereas Washington is increasing its military presence in the South China Sea, many of the other claimants have few naval and coast guard resources of their own (hence U.S. partner capacity investments). With additional security issues around the world ranging from the Islamic State (also known as ISIS) to Ukraine, Washington can prioritize the Pacific but cannot ignore the rest of the world, and leading from within a diverse balancing coalition doesn’t produce easy gains or quick fixes.

PROVOCATIVE

While Washington has been investing in a long-term multilateral political strategy, China has focused on unilateral short-term changes to the military balance in the South China Sea. Beijing built 3,000 acres of new South China Sea land over a period of just 18 months and has been paving three new runways at breakneck speed. And China is clearly installing military and dual-use equipment on its islands. More disturbing than the installations themselves is the fact that Beijing claims they are not militarily provocative at all. If, in Beijing’s book, surface-to-air missiles are purely defensive, however, it is safe to assume that more dangerous deployments will soon follow.

A satellite image released by the Asian Maritime Transparency Initiative at Washington's Center for Strategic and International Studies shows construction of possible radar tower facilities in the Spratly Islands in the disputed South China Sea in this image released on February 23, 2016. Reuters Over the last few years, China’s South China Sea strategy has relied on what strategists refer to as “salami slicing” in “gray zones.” Beijing has advanced its interests opportunistically and incrementally, keeping its activities below the threshold of open conflict that would provoke intervention by the United States. China has moved an oil rig into waters disputed with Vietnam, wrested the Scarborough Shoal from the Philippines, and dredged up seven artificial Spratly Islands. These activities have all provoked a collective outcry but little active response because Beijing possesses several key advantages.

First, China’s South China Sea approach relies on opportunism. Beijing has adopted tactics that are unlikely to cause full-blown conflict and implemented them at times and places when it is unlikely to meet with serious pushback. Related is the fact that China is the first mover in its efforts to shift the status quo in the South China Sea (although Chinese officials would almost certainly disagree with this characterization). Beijing chooses when it will make its next South China Sea move, and the United States and its partners are forced to react. The tempo of its activities also provides China with an advantage: unlike U.S. diplomatic or security efforts, which have long time horizons, Beijing’s assertiveness proceeds in shorter bursts. These three characteristics have all been on display in the Spratly Islands, where China reclaimed new land incredibly quickly and has since dialed up and down its building as its interests and the international environment suit. Salami slicing has produced significant gains for Beijing, and although they have come with diplomatic and reputational costs, China seems to have calculated that the costs are worth the longer-term gains.

With its recent deployments, however, China has moved beyond this gray area. Analysts have long worried that China is developing an anti-access/area denial (A2/AD) capability that aims to keep foreign powers from entering or operating in the waters close to its shores in the event of a major conflict. For A2/AD, China would need sophisticated radar to monitor the area and surface-to-air and anti-ship cruise missiles to ward off an outside power. The two surface-to-air batteries that China has recently rolled out will surely not keep the United States away, but chances are good that there will be more where these came from, and Washington and its partners need no longer ponder China’s intentions for its island outposts.

A satellite image released by the Asian Maritime Transparency Initiative at Washington's Center for Strategic and International Studies shows construction of possible radar tower facilities in the Spratly Islands in the disputed South China Sea in this image released on February 23, 2016. Reuters WELL ORDERED

Washington’s efforts have succeeded at rallying support behind the rules of the regional order, and they will likely bear fruit when its comes to longer-term U.S. military presence in the area. But these efforts have not prevented China from shifting the military balance in the South China Sea in the near term. If the United States and its partners want to halt China’s worrisome advances, they must focus on closing the gap between the political and military balances. This means translating the growing political consensus into near-term multilateral action in the South China Sea, with the United States at the helm.

First, with respect to the near-term military balance, Washington must prepare itself and its partners for a coordinated push against additional Chinese encroachments. If China does declare an ADIZ over the Paracel Islands, the Spratly Islands, or a broad swath of the South China Sea, it would be destabilizing because of the sheer number of claimants and disputed territories it would encompass. Washington should not only lay the diplomatic groundwork for regional states to protest an ADIZ but begin to make plans with partners to conduct multilateral military operations that will contest the zone on a regular basis. It should also coordinate with ASEAN countries as well as Japan and Australia to make sure that partners have consistent and coordinated policies as to how their commercial airlines will treat this zone.

Second, the United States may need to rethink whether China’s continued assertiveness should be met with costs outside of the South China Sea. The United States and China have a deep and multifaceted relationship, including on important security issues where they must cooperate, but Washington may increasingly find that it needs to hold the other aspects of the relationship at risk to gain leverage. This could include cancellation of high-level visits and invitations to military exercises, as well as other symbols of China’s great power status that are highly valued in Beijing.

Third, Washington must expand its own strategy for the military balance in the South China Sea. U.S. military and civilian leaders have placed a great deal of emphasis on freedom of navigation operations in these waters, which contest spurious claims to water and airspace. Although such operations should absolutely be conducted routinely, they are mostly intended to send discrete legal messages. If China continues to arm its outposts, Washington and its partners will also want to remind Beijing that they are monitoring its activities and stand prepared to respond to the use of force. They will want to conduct consistent surveillance and reconnaissance operations by sea and air and to improve their coordination in the South China Sea.

Fourth, Washington should signal to Beijing that China’s militarization in the South China Sea may ultimately force the United States to change its own strategy. For years, U.S. policymakers have tried to get South China Sea claimant states to exercise restraint, convincing them to halt their own land reclamation or other building on islands, with the ultimate goal of achieving a binding code of conduct for all. Such a code must remain a goal, but Washington may increasingly have an interest in seeing its partners exercise less restraint in the South China Sea. Although it should not explicitly encourage the Philippines or Vietnam to arm its own outposts, it can communicate to Beijing that China’s actions are eroding the United States’ interest in restraining its partners.

None of these are good options. Contesting a South China Sea ADIZ, tying Beijing’s behavior to other aspects of the bilateral relationship, and assenting to Vietnamese or Philippine militarization would all be steps that Washington should be and would be loath to take. There is also no guarantee that these steps will halt China’s rapid advances, and a stronger stand necessarily introduces additional risk into the U.S.-Chinese relationship, which will remain a vital one for years to come. The emerging alternative, however, is effective Chinese control of the waters and skies of the Paracels and Spratlys, backed up by dangerous weapons. This is no alternative at all and will surely not bring peace or stability to the region or world.