The Scarborough shoal, an obscure feature 120 nautical miles west of Luzon in the South China Sea, has been an unlikely locus of concern over a potential clash between the U.S. and China. Tension first flared there in 2012 when China effectively evicted Filipino fishermen from the shoal, which surrounds a fish-rich lagoon covering nearly 60 square miles. In March, the head of the U.S. Navy told reporters the Navy was concerned the Scarborough Shoal was “a next possible area of reclamation.” The possibility that China might build facilities capable of hosting jets or missiles within reach of Manila raises the specter of military clash with a U.S. treaty ally that could bring the U.S and China to blows. There is evidence the U.S. has worked behind the scenes to deter Chinese expansion at Scarborough Shoal and broker some arrangement between China and the Philippines over its use. However, the policies incoming populist Philippine President Rodrigo Duterte suggests he will implement may neuter U.S. efforts to keep China from expanding its South China Sea military infrastructure.
Chinese buildup on Scarborough Shoal could pose a distinct, if limited, threat to the Philippines. The facilities China has built in the Spratly Islands are capable of supporting major force projection capability, but remain unarmed for now, in arguable compliance with Chinese President Xi’s 2015 pledge not to militarize features there. Scarborough Shoal, however, is not a part of the Spratly chain, so Chinese facilities built there might be unambiguously armed like its bases in the Paracels. While the relative isolation of the shoal means Chinese forces would be both highly exposed to counterattack and easily starved of re-supply, Chinese missiles and jets would nonetheless be within striking distance of some of the Philippines’ most important naval and air bases, as well as Manila. And as a former head of the U.S. Navy suggested, after failing to stop China’s fait accompli base construction in the Spratlys, the U.S. is especially sensitive to preventing any new Chinese military outposts in the region.
Outgoing Philippine President Aquino’s commitment to preventing Chinese construction at Scarborough Shoal has been unequivocal. But before the May election, President-elect Duterte sounded ambivalent about the dispute. While insisting that “it [Scarborough Shoal] is ours, period” he also hinted he would “shut up” about the dispute in return for infrastructure aid to build railroads and insisted that “I will not waste the lives of Filipinos” over it. Now having won the presidency, in part with the support of fishermen hopeful he would help return their old fishing rights at Scarborough Shoal, Duterte reiterated that he would “never surrender” the shoal to China, but seems unwilling to incur any costs to protect it. Speaking to reporters this week, Duterte–who will be inaugurated at the end of June–said explicitly that “I will not go to war because of the Scarborough Shoal,” and that a clash with China over the shoal would be “a massacre.”
This is not the first time China has made moves against disputed islands claimed by a U.S. treaty ally. In the East China Sea, China claims the Japanese-held Senkakus, around which it has claimed a formal maritime boundary with the U.N., and makes almost daily incursions into surrounding waters with its coast guard and aircraft. But lest China attempt anything more overt against the Senkakus, which Beijing calls the Diaoyu, both U.S. President Obama and Defense Secretary Carter have publicly pledged that the U.S. will defend the islands under the terms of the U.S.-Japan Security Treaty. However, the U.S. has pointedly refrained from making a similar pledge with respect to the Scarborough Shoal and its Mutual Defense Treaty (MDT) with the Philippines. Instead, it has maintained a careful ambiguity over its commitment to keeping the shoal free of Chinese construction.
Nevertheless, President Aquino said recently that the U.S. must act if China moves against the shoal, and the circumstantial evidence suggests the U.S. has told China that it would. Administration sources say Obama personally warned President Xi Jinping against provocations at Scarborough Shoal at a meeting in Washington. The Chairman of the Joint Chiefs of Staff reportedly asked Admiral Harry Harris, head of U.S. Pacific Command, whether he would go to war over the Scarborough Shoal earlier this year. Asked how he responded, the Admiral’s coy non-answer (“it is good that my voice is low”) reinforced the impression that the U.S. had signaled China to expect real opposition to reclaiming the shoal.
The basis for U.S. military action against Chinese construction on Scarborough Shoal, and therefore the credibility of any deterrent signals it has given Beijing, is under the provisions of the MDT with the Philippines. The obligation to act depends on one party being attacked, which the treaty defines as armed attack on either a party’s “metropolitan territory” or “island territory under its jurisdiction,” or on its “armed forces, public vessels, or aircraft.” President-elect Duterte’s statements make it hard for likely Chinese actions to meet those criteria.
Significantly, Duterte has said he does not consider the Scarborough Shoal dispute to be over territory, but a matter of respecting Filipino rights within its Exclusive Economic Zone (EEZ), even though legal experts believe the shoal is entitled to territorial status under the U.N. Law of the Sea. Duterte’s interpretation thus needlessly cedes the right to define potential Chinese aggression at the shoal as an attack on “territory” under the terms of the MDT.
In defining the dispute in terms of EEZ rights, Duterte also said he would use his coast guard, not his navy to assert Philippine rights at the shoal. As “public vessels,” attacks against coast guard cutters are covered under the terms of the MDT. However, the Philippine Coast Guard is woefully over-matched by the Chinese Coast Guard; its largest cutter is nearly 20 times smaller than China’s largest. The level of force China would notionally use against it is so low that a proportional U.S. response is unlikely to have much reciprocal or deterrent effect. Further, if the U.S. Navy were to get involved against the Chinese Coast Guard, it would end up looking like the bully, not China. In any case, if China were to use its much larger coast guard cutters to push Filipino vessels out of the way, it isn’t clear this would meet the standard of “armed attack” under the MDT.
Finally, the point Duterte has been clearest and most consistent on—that he would not risk Filipino lives against China over the shoal—means he is unlikely to allow his forces to take any action that provokes China in the first place. If China perceived even an ambiguous threat of U.S. intervention on behalf of the Philippines, Duterte’s statements effectively remove it. Admiral Blair, a former head of U.S. Pacific Command, recently told reporters that “If the Chinese push [at Scarborough Shoal] …there’s going to be trouble,” and that Chinese construction there was, geopolitically, “a pink line, if not a red line” for the U.S. But the Philippines would also need to consider Scarborough Shoal a red line in order to give the U.S. the legitimacy to act. If his views hold once in office, it doesn’t appear the Duterte administration will provide that red line, undercutting the credibility of U.S. deterrence. If that happens, U.S. efforts to dissuade China from occupying and reclaiming Scarborough Shoal will need to get more creative.
Steven Stashwick is a writer and analyst based in New York City. He spent ten years on active duty as a U.S. naval officer with multiple deployments to the Western Pacific. He writes about maritime and security affairs in East Asia and serves in the U.S. Navy Reserve. The views expressed are his own. Follow him on Twitter.