The latest saga in the decades-long standoff over Second Thomas Shoal—known as Ayungin in the Philippines and Ren’ai Jiao in China—happened as Philippine boats attempted to resupply a contingent of marines in the Spratly Islands in June, the Philippine Daily Inquirer said in a July 4 report.

During a June 21 rotation and resupply mission, China Coast Guard ships No. 4302 and No. 5304 tailed wooden boats headed for BRP Sierra Madre, a former U.S. Navy landing ship that the Philippine Navy deliberately ran aground near the shoal in 1999 to serve as an outpost. The shoal is about 105 nautical miles off Palawan in the West Philippine Sea—Manila’s term for the eastern portion of the South China Sea that falls within the Philippines’ exclusive economic zone.

The Spratly Islands are contested by Brunei, Malaysia, Taiwan, Vietnam, China, and the Philippines, but it’s Beijing and Manila that have wrestled for control over Second Thomas Shoal in the last decades. The Sierra Madre represents ongoing Philippine attempts to assert sovereignty and control over the shoal. It doesn’t move; the marines stationed on board are routinely rotated off the vessel, which is resupplied with small boats in order to cool tensions with China.

According to the Inquirer, Chinese vessels that operate regularly in the area, which Beijing claims in its entirety, generally don’t obstruct the resupply of rations. However, they protest the delivery of construction materials that could be used to repair and fortify the rusting warship.

The crew of Sierra Madre was told to “seriously consider the solemn stand of the Chinese government,” during its latest supply mission, the newspaper said.

“If you insist on making trouble [in] your own way, you will take responsibility for all these consequences arising therefore,” China Coast Guard ship No. 5304 warned over the radio, in a move one Philippine Marine described as “bullying.”

As China’s hard power grows in the air and sea, managing overlapping disputes in the South China Sea has become a pressing issue for littoral states like the Philippines, which like many neighbors count China as its most important trading partner. During their 2012 clash over Scarborough Shoal, now under Chinese control, Beijing imposed indirect economic sanctions on Philippine exports.

Beijing asserts sovereignty over nearly all of the South China Sea via its “nine-dash line,” despite the Permanent Court of Arbitration’s rejection of these claims in 2016 in the outcome of Philippines v. China—a verdict Manila is finding almost impossible to enforce.

In 2021, disputes over Second Thomas Shoal saw Chinese vessels accused of firing water cannons on Philippine supply boats. The incident triggered reminders out of Manila and Washington about the U.S.-Philippines Mutual Defense Treaty, which covers attacks on the Philippine military in the South China Sea.

On June 28, the Philippines’ then-outgoing Defense Secretary Delfin Lorenzana said the supply runs would continue despite Chinese protests.

“We have been resupplying that detachment for the past 20 years. Our people need to repair their living quarters,” he said. “[China has] a lot of conditions…But we will continue to resupply the Sierra Madre. We will not stop.”

Beijing claims indisputable sovereignty over the South China Sea and argues its vessels have a right to enforce controls around Second Thomas Shoal and other maritime zones.

Major Western governments—most recently the Group of Seven—rely on unimpeded trade routes in the South China Sea to sustain their economies. They support Manila’s position and find Beijing’s claims inconsistent with the United Nations Convention on the Law of the Sea, or UNCLOS.

In the leaders’ joint statement released last week, the G7 said: “We remain seriously concerned about the situation in the East and South China Seas. We strongly oppose any unilateral attempts to change the status quo by force or coercion that increase tensions.”

“We stress that there is no legal basis for China’s expansive maritime claims in the South China Sea. In this regard, we urge China to fully comply with the arbitral award of 12 July 2016 and to respect navigational rights and freedoms enshrined in UNCLOS,” the statement said.