China’s naval pressure campaign against rival nations in the South China Sea has reached unprecedented heights since yearly short-term moratoriums on fishing were lifted, with Chinese ships shadowing Western warships in the region and seeking to interrupt maritime resupply on a submerged, Philippine-claimed island.

The People’s Liberation Army Navy’s ongoing blockade of the Second Thomas Shoal, a submerged reef that’s part of the Spratly Island chain in the West Philippine Sea, has become a rallying point for Southeast Asian countries concerned about China’s harassment of smaller nations on the high seas. In early August, the Philippines accused Chinese vessels of firing water cannons at its Coast Guard ships as they attempted to resupply the reef.

It was a major display of force by China, including six large Coast Guard ships and four naval vessels. “It looked to be a calculated show of force by China,” said Ray Powell, the director of SeaLight, a Stanford University project focused on China’s maritime gray zone activities. “It looked like China was trying to send the Philippines a message that playtime is over. We’re bringing in the big guns.”

China basically claims almost all of the South China Sea, asserting “indisputable sovereignty” over the Spratly Islands, the Paracel Islands, and the Scarborough Shoal via a so-called nine-dash line ringing the sea. While those claims are disputed by almost every other country in the region, including Taiwan, Brunei, Indonesia, Malaysia, the Philippines, and Vietnam, China has spent more than a decade creating facts on the ground by artificially enhancing atolls and reefs, turning them into airfields and ports.

The crisis, which has been ongoing since Chinese authorities lifted their annual fishing moratorium in mid-August, has seen People’s Liberation Army-backed maritime militia forces actively blocking Philippine Coast Guard resupply vessels from landing on the shoal, where the Philippines periodically needs to resupply the BRP Sierra Madre, a World War II-era U.S.-made tank landing ship. Manila ran the Sierra Madre aground on top of the submerged reef in 1999 to help support its legal claim to it.

It’s not the first recent maritime flare-up between Chinese and Philippine sailors. Even during the administration of the mercurial former Philippine President Rodrigo Duterte, who sought to strengthen relations with Beijing and threatened to boot a rotating presence of U.S. troops from the archipelago, Manila filed a formal diplomatic protest in 2021, when more than 200 Chinese fishing boats laid anchor at the disputed Whitsun Reef in the Spratly chain. The Philippines also sought arbitration at the Hague over the territorial dispute with China in the sea in 2016.

But with new Philippine President Bongbong Marcos in power and taking a more hawkish tack toward China, the tensions have kicked up another notch. Through the summer, China repositioned large portions of its maritime militia forces to operate out of Mischief Reef, according to Powell. Mischief, an atoll in the South China Sea that has been developed by Beijing and armed with anti-aircraft missiles, is about 25 miles from Second Thomas Shoal.

China also buttressed those militias with more forces near Sabina Shoal, another disputed shoal, and Thitu Island, the second-largest of the Spratlys. And it’s not just shadowing and water cannons; China has also fired blinding lasers to daze Philippine vessels at least twice this year.

And Manila has dusted off Vietnam’s playbook from 2014, when Chinese vessels harassed Hanoi’s navy over an oil rig dispute in the South China Sea, by naming and shaming China directly. “When it comes to international relations, anything that you publicize that has a reputational cost for China, hits a nerve with the Chinese,” Philippine Coast Guard spokesman Commodore Jay Tarriela told Bloomberg in August.

The push against Second Thomas Shoal is also a sign to experts that China’s navy can more effectively sustain itself at sea from disputed islands in the South China Sea. And just as China’s air force has used constant incursions into Taiwan’s air defense identification zone as a tactic to burn out Taipei’s pilots, it is using the pressure campaign at sea to exhaust Philippine forces.

“They couldn’t really flex their muscles against the Filipinos, the Malaysians, [and] the Indonesians until after they built up the islands in the South China Sea, and that’s really why they did that,” said Brent Sadler, a senior research fellow for naval warfare and advanced technology at the Heritage Foundation and a former U.S. naval attach? in Malaysia. “Now they can keep those cutters and those patrol boats and fishing boats out there a lot more frequently [and] actually start to wear down the Malaysian and Filipinos just because they can keep a constant presence where the other guys don’t have as many platforms.”

And the more that China uses Coast Guard and maritime militia forces to harass the Philippine and other regional navies, the more routine China’s aggressive posture becomes. “The Chinese just keep coming at them and messing with them,” Sadler said. “It becomes like a new normal.” Chinese military strategists believe that under the constant pressure, the United States would go away rather than continue to contest its maritime control.

Even with the Philippines adamant that it will continue to resupply the sunken reef despite Chinese harassment, experts are worried that the Biden administration needs a longer-term solution to the recurring crisis, which has bedeviled the last three U.S. administrations.

“The Philippines and the U.S. are going to have to come up with a solution for Second Thomas Shoal,” said Powell. “Because otherwise, time and the elements will solve it for them, and at that point, China will just own the shoal.”