Inside the International Contest Over the Most Important Waterway In the World

In the South China Sea, near the reefs known as Mischief and North Danger, a detachment of seven Philippine soldiers and seven dogs guard a coral-fringed sandbar. The cay is called Flat Island, but the “island” part is a bit misleading.

A leisurely stroll around the second smallest islet of the Spratlys–a scattering of rocks, reefs, shoals and islands flung across the South China Sea–takes just minutes. Since the Philippine navy sends fresh water, fuel and other provisions only once every two months, the soldiers must survive on their spearfishing catch and filched seagull eggs. “It’s a beach resort,” says Corporal Ariel Lego, “with no resort.”

Flat Island is too hot, too salty and too small to sustain human life. Yet this spit of sand outfitted with nothing more than a pair of concrete garrisons and a wooden hut is claimed by four governments: China’s, Vietnam’s, Taiwan’s and that of the Philippines, which occupies it. For years, activity around this isolated outpost, a full day’s sail from the Philippine island of Palawan, was limited to perhaps a daily pass by a Chinese, Vietnamese or Philippine fishing trawler. But in early May, Chinese coast guard vessels glided past Flat Island, part of an increasingly visible and adventurous maritime foray by the region’s biggest power.

A few days later, on May 10, a U.S. guided-missile destroyer cruised past Fiery Cross Reef, another disputed Spratly feature. Once just two rocks jutting out at high tide, the shoal has been transformed into a 680-acre (275 hectare) landmass, one of seven artificial islands the Chinese have constructed in the South China Sea since 2014. Passing within 12 nautical miles of Fiery Cross, the U.S.S. William P. Lawrence engaged in what the Pentagon terms a “freedom-of-navigation operation [to] challenge excessive maritime claims.” Beijing responded by scrambling fighter jets, protesting that the U.S. warship had “illegally entered waters near the relevant reef … and jeopardized regional peace and stability.” An op-ed in the state-run China Daily warned that “the moves by the U.S. in the South China Sea smack of its arrogance as the world’s sole superpower.”

The South China Sea ranks as one of the world’s most strategically vital maritime spaces–and one of its most contested. More than $5 trillion in trade flows through its waters each year, one-third of all global maritime commerce. The Strait of Malacca, the choke point that links the Indian and Pacific oceans at the southern end of the South China Sea, handles four times as much oil as the better-known Suez Canal. In an era when the world is ever hungrier for seafood, the South China Sea teems with at least one-tenth of the worldwide fishing stock; its azure depths boast untapped oil and natural-gas deposits. No wonder six governments–those of China, Vietnam, the Philippines, Taiwan, Malaysia and Brunei–have laid competing claims to various pinpricks of territory in the 3.5 million-sq.-km. waterway.

A Cold War–style showdown is now coalescing in the South China Sea, between the world’s established superpower and its presumptive one. While the U.S. is not a claimant to the sea’s specks of land, America’s navy and merchants have long cruised its waters freely. Washington contends that it is keeping vital sea-lanes safe and open for everyone. A rising China, meanwhile, is more assertively pursuing what it considers its birthright: a Monroe Doctrine–like sway over nearly the entire South China Sea and indisputable sovereignty over its sprinkling of reefs, rocks and isles. “The South China Sea dispute is about who is going to be top dog in Asia,” says Ian Storey, a senior fellow at the ISEAS-Yusof Ishak Institute in Singapore. “It’s the issue in global geopolitics.”

In May, a Pentagon report noted that Chinese dredgers have reclaimed at least 3,200 acres (1,295 hectares) in the Spratlys over the past couple of years. (All the other claimants combined reclaimed just 50 acres, or 20 hectares, over the same period.) A “Great Wall of Sand” is what Admiral Harry Harris Jr., head of the U.S. Pacific Command, has dubbed the Chinese building spree. “In my opinion, China is clearly militarizing the South China Sea,” Harris told Congress in late February, after Beijing had stationed radar and surface-to-air missile batteries in the Paracels, another disputed South China Sea archipelago. “You’d have to believe in a flat earth to believe otherwise.”

In response, the U.S. has stepped up its own South China Sea patrols, both by sea and air. On May 17, as a U.S. reconnaissance plane flew in what Washington says was international airspace over the South China Sea, a pair of Chinese fighter jets buzzed it, coming within 50 ft. (15 m) of the American aircraft in what the Pentagon called an “unsafe” intercept. Chinese Foreign Ministry spokesman Hong Lei had a different take. “U.S. military vessels and aircraft frequently carry out reconnaissance in Chinese coastal waters,” he said, “seriously endangering Chinese maritime and airspace security.”

This is dangerous stuff: an aerial collision in 2001 over the South China Sea ended with a dead Chinese fighter pilot and an American crew that spent 11 days in detention on the Chinese island province of Hainan, sparking a bilateral crisis. “Right now, we are witnessing the evolution of the security architecture in the Asia-Pacific,” says Wu Shicun, president of the Chinese government–funded National Institute for South China Sea Studies. “If the South China Sea issue is not managed well, there will certainly be a confrontation between China and the United States.”

The notion that controlling a piece of land affords a nation rights over the surrounding sea originates from the imperial age of the 17th century, when European powers wanted to monopolize their colonial spoils. Freedom of navigation, the right to traverse the seas unimpeded, flowed from the same rule book. But China, which began to decay under a waning dynasty, was a victim of empire–a narrative that underlines the country’s South China Sea claims, and much of its foreign policy. For too long, imperial powers preyed upon a weakened China, stealing away territory–as the British did with Hong Kong–and humiliating its populace. Now, under President Xi Jinping, a resurgent nation is defending what it considers its national patrimony. “Islands in the South China Sea have been China’s territory since ancient times,” Xi said last fall. “The Chinese government must take responsibility to safeguard its territorial sovereignty.”

China claims nearly all of the South China Sea as its own through maps marked with a U-shaped, nine-dash line that dates from 1947. The dotted boundary may have reflected one mapmaker’s impression of China’s historical claims, but it did not reflect the geopolitical reality of the mid–20th century. Even today, Beijing has not clarified in international forums just what the contentious line means. Is it just the bits of land and reef with the dashes that the country claims? Or is it all waters, as implied by official Chinese proclamations about “traditional fishing grounds” close to other nations’ coastlines?

Disputed maps, though, matter less than Beijing’s rapid island-building in the South China Sea. Under the U.N. Convention on the Law of the Sea–which China has signed but which the U.S. has not, undercutting American authority on the matter–only a naturally formed island that can support human or economic life can justify a claim of an “exclusive economic zone,” or EEZ, which can extend as much as 200 nautical miles. An EEZ is crucial: it grants a coastal nation sovereign rights to all natural resources within those waters, though other nations’ vessels are allowed to pass through.

But what recourse is there now that many of the reefs and rocks controlled by China have been turned into weaponized islands? In 2013, the Philippine government filed a case with a U.N. tribunal in the Hague arguing against Beijing’s South China Sea claims. A decision from the Permanent Court of Arbitration is expected in the coming weeks, further raising regional tensions. Beijing, though, has already said it won’t respect the ruling, which will likely at least partly favor the Philippines. Nor does the tribunal have any powers of enforcement.

China’s South China Sea construction frenzy has prompted many Asian nations long leery of American hegemony to move toward the U.S. China may now be their largest trading partner, but no country wants to return to an ancient era when a Chinese emperor commanded tributary states across the continent. “I’m sure a lot of other countries are wondering, Will this ever befall us, will this limit our ability to chart our own course?” outgoing Philippine President Benigno Aquino III tells TIME, referring to China’s actions in the South China Sea. “There is a theory that China will tend to push, and if you bend, they will push some more.”

For now, Washington is not ceding any ground. On a recent sweltering day, the U.S.S. John C. Stennis, a Nimitz-class nuclear-powered aircraft carrier that considers itself “4.5 acres of sovereign U.S. territory,” plowed through the South China Sea. Escorting the Stennis, which was carrying more than 3,000 military personnel, were a trio of guided-missile destroyers and an Aegis cruiser. Jets strafed the sea with bombs, sending white spray into tropical air. “We’re committed to security at sea,” says Rear Admiral Marcus Hitchcock, commander of the Stennis strike group, which includes the William P. Lawrence, the destroyer that cruised close to Fiery Cross Reef. “We are very invested in the economic development and building of commerce in the region.”

The U.S. Navy has been a force in the waters of the Asia-Pacific region since 1853. That was the year U.S. Commodore Matthew Perry steamed into a Japanese harbor and used gunboat diplomacy to force the island nation out of its self-imposed isolation. Long tilted toward the Atlantic, the U.S. soon boasted Pacific holdings like Hawaii, Guam and the Philippines, which it won as spoils in the Spanish-American War. World War II cemented U.S. naval dominance in the world’s largest ocean as the Pacific began to feel like an American lake. Of the U.S.’s seven collective-defense treaties around the world, five are in the Asia-Pacific.

Born in Hawaii and partly raised in Indonesia, Barack Obama came to office vowing to serve as a Pacific President for a Pacific century. While the Middle East refused to release Obama’s foreign policy, he presided over a so-called pivot to Asia that included shifting a greater percentage of American troops to the Pacific. In 2010, then U.S. Secretary of State Hillary Clinton announced at a regional forum in Vietnam that the U.S. “has a national interest in freedom of navigation … and respect for international law in the South China Sea.” Beijing, though, views the “rebalance,” as the pivot was later renamed, as nothing more than American containment by a more polite name. “By using the South China Sea to contain China, America has turned a regional issue into a global issue,” says retired Colonel Liu Mingfu, a Chinese military commentator. “Too many countries are now involved, and that’s dangerous.”

Defense spending in Southeast Asia has jumped as unease over China grows. Last year, Indonesia, Vietnam and the Philippines were among the 10 countries with the world’s fastest-growing military budgets, according to IHS Jane’s, the defense publisher. “I think other Asian countries have been startled by the speed and uncompromising way with which China is asserting itself in the South China Sea,” says Bilahari Kausikan, a veteran Singaporean diplomat. “It makes us wonder whether Beijing really believes the Pacific is big enough for the U.S. and China.”

The Philippines, which in the early 1990s ended a long-standing American military presence, is welcoming back U.S. troops, even if the country’s President-elect, Rodrigo Duterte, seems keen to repair economic ties with Beijing. In Vietnam–whose communist soldiers repelled U.S. forces decades ago–Obama on May 23 lifted an arms embargo that had been in place since 1984. Though he insisted the decision was “not based on China,” few observers agreed. “It’s all about China,” says Anthony Zinni, a retired four-star U.S. Marine general who fought in Vietnam. “No matter how much he denies it.” Xinhua, China’s state news agency, concurred: “The United States has come to the belief that [Vietnam] could be suitable to help project Washington’s will over the South China Sea issue.”

In a May 24 speech in Hanoi, Obama was pointed when it came to the South China Sea.”Nations are sovereign, and no matter how large or small a nation may be, its territory should be respected,” he said. “Big nations should not bully smaller ones.” Two months earlier, he had cautioned Xi in a meeting against further reclamation in the South China Sea, according to U.S. defense officials. The warning centered on Scarborough Shoal, which is located 185 nautical miles west of Manila, the Philippine capital. Four years ago, the Chinese seized control of the reef after a failed diplomatic initiative by Washington. Now Chinese military commentators have gone online to discuss plans for dredging Scarborough to turn it into yet another artificial island.

But what rising power will blunt its ambitions, especially in its own backyard? While China has just a single aircraft carrier, a retrofitted Ukrainian ship that was once considered for use as a floating casino, it is assembling a blue-water navy–one capable of traversing the open oceans–and building a second aircraft carrier that will patrol the South China Sea. The Chinese are also developing the Dongfeng-21D anti-ship missile, which Pentagon officials fear could disable, and even sink, huge warships like the Stennis. As it is, half a dozen Chinese soldiers could probably overwhelm Flat Island without breaking a sweat, aside from the heat. And for all of Obama’s commitment to Asia, the White House remained silent for months on China’s reef reclamation. “The United States certainly isn’t willing to go to war with China over these rocks and reefs,” says Storey. “That leaves America with pretty limited options.”

The Chinese may be willing to adopt a longer perspective, even if they take short-term measures like the rare move of denying the U.S.S. John C. Stennis a Hong Kong port visit in late April. “Like the tide that comes and goes, none of these attempts will have any impact,” said Chinese Foreign Minister Wang Yi in March, as the Stennis completed an earlier pass through the South China Sea. “History will prove who is merely the guest and who is the real host.”

Before there were nations in the South China Sea, with their borders and EEZs, there were fishermen. On Vietnam’s remote Ly Son island, Nguyen Quoc Trinh, head of the local fishermen’s association, describes how mysterious Chinese vessels have attacked his union’s boats, ramming their matchstick hulls with steel prows or forcing the Vietnamese by gunpoint to evacuate contested areas. “China makes it impossible because we cannot fish where we used to fish for generations,” he says. In early May, yet another Vietnamese trawler operating in the disputed Paracels archipelago–which Chinese naval forces gained control over in a bloody but brief clash with the South Vietnamese in 1974–limped to shore after it was struck by a Chinese ship.

Among the colorful trawlers nestled at Tanmen port on China’s Hainan Island loom gray, steel-hulled behemoths. Many conspicuously lack fishing nets, and Tanmen locals refer to them as “military boats.” In 2013, Xi visited Tanmen and praised the local maritime militia, composed of well-subsidized fishermen and decommissioned soldiers, for plying distant waters. He urged its members to “support the construction of islands and reefs,” according to state media.

Roger that. Boats from the Tanmen militia already had stormed Scarborough Shoal in the run-up to China’s successful takeover. In late March, around 100 Chinese fishing boats showed up in waters near the Malaysian coastline, guarded by a pair of Chinese coast guard ships. “Chinese trawlers are in the relevant waters carrying out normal fishing activities,” maintained the Chinese Foreign Ministry. But not all Tanmen locals agree. “It’s not about whether there are enough fish in the area for so many countries to share,” says Tanmen fisherman Chen Yiquan, who spent a year in a Philippine jail on charges of poaching sea turtles. “It’s about politics. Now there are more militias than real fishermen in the region.”

These paramilitary and quasi-civilian fleets have further muddied South China Sea waters. In 2009, Chinese fishing boats buzzed the Impeccable, a U.S. surveillance ship operating in the South China Sea, about 75 miles (120 km) from Hainan. The Chinese coast guard regularly directs water-cannon sprays at foreign fishing vessels and maritime authorities. In March, after an Indonesian patrol boat apprehended a Chinese trawler that Jakarta said was illegally fishing in its waters, a Chinese coast guard vessel muscled in to free the Chinese boat from the towline connected to the Indonesian ship. The Chinese Foreign Ministry called the waters where the incident took place–off the coast of one of Indonesia’s undisputed islands–its “traditional fishing grounds.” “The Chinese government is using these boats as military proxies in the South China Sea,” says Bonnie Glaser, a senior advisor at the Center for Strategic and International Studies in Washington.”One wrong move, and they could provoke a serious crisis.”

As U.S. aircraft carrier strike groups ply the sea, Chinese cruise ships ferry Chinese tourists to the Paracels. In March, Wang Xinjian, a Chinese army veteran, boarded the Coconut Princess. “I felt like I was in a fairyland,” he says of his visit. “Any country that wants to take away our territory is daydreaming.” In early May, one of China’s most popular folksingers gave a concert on Fiery Cross Reef, with a repertoire including “Ode to the South Sea Defenders.”

By contrast, the Philippine navy is perennially short of funds, bases and even boats–despite a 15% hike in defense spending from 2014 to 2015. When U.S. Secretary of Defense Ashton Carter announced onboard the Stennis in April that the U.S. and the Philippines would conduct joint patrols, it was unclear where Manila would find the vessels to embark on such exercises, at least until orders for new warships are filled. One of the Philippines’ fleet of geriatric vessels–a U.S. cast-off of World War II vintage–has been parked since 1999 on the contested Second Thomas Shoal to serve as a military base. The rusting Sierra Madre houses seven soldiers and many more rats. “We cannot match the might of the Chinese military,” says Colonel Arnel Duco, a deputy commander of the Philippine Western Command. “So we need to be innovative and use every old ship and palm tree at our disposal.”

Sergeant Roland Wong was deployed for six months on the Sierra Madre. It was, the Philippine soldier says, “a job but a very lonely, very difficult job.” Wong now serves on Nanshan Island, another of the Spratlys. Unlike nearby Flat Island, Nanshan supports a lagoon with brackish water that soldiers can use to shower. The island is home to a seagull sanctuary, and the air is thick with birdcall and the stench of guano. Yet this coral-ringed isle, deep in the South China Sea, sits at the fulcrum of global geopolitics. “We are so far from everywhere,” says Wong, looking at a destroyed bulldozer that sits like an urban sculpture in the middle of Nanshan, a testament to the Philippine navy’s corroded dreams. “But we are all scared that the Chinese will come one day.”

–With reporting by YANG SIQI/TANMEN and MARK THOMPSON/WASHINGTON