China is testing the limits of U.S.-Philippines defense pact

China has stepped up its aggression against the Philippines in the contested waters of the South China Sea, calling into question the strength of American deterrence, according to policy analysts.

Last week, the Chinese coast guard seized two Filipino ships on a resupply mission to an outpost on the Second Thomas Shoal in the Spratly Islands, severely injuring a navy personnel, according to Philippine officials. The shoal is claimed by both Manila and Beijing.

The area has seen several clashes over the past months. Experts say the latest incident represents an escalation and shows the limitations of the U.S.-Philippines Mutual Defense Treaty signed in 1951.

“The failure of the MDT to deter the [latest confrontation] shows the vagueness in the conveyed commitments of the two parties,” said Chester Cabalza, president and founder of the Philippines-based think tank International Development and Security Cooperation.

Last year, the Philippines and U.S. released new “Bilateral Defense Guidelines ,” reaffirming that an “armed attack” in the South China Sea on Filipino vessels would invoke mutual defense obligations of the U.S.

China, on its part, has been careful not to trigger the MDT by avoiding the use of guns, instead employing ” gray zone” tactics — coercive actions that fall short of an armed conflict — at the Second Thomas Shoal. These reportedly have included the use of water cannons and ramming into Philippine boats.

Those guidelines are consistent with the interpretation of the MDT in a report by the U.S. Indo-Pacific Command that was unclassified last year.

However, according to Heydarian, a muted Philippine reaction to last week’s clash could be a sign of its apprehensions with regard to invoking the mutual defense treaty.

“The Philippine Government is confronted with a huge dilemma. It wants greater reassurance from the United States, but it’s likely not getting that, and it also wants to avoid unwanted escalation,” said Heydarian.

“It’s extremely important for the Philippines and U.S. to signal that Filipino troops are empowered and sanctioned to use live firearms to defend themselves, and that usage of live firearms by China would immediately trigger the MDT,” he added.

However, according to Abdul Rahman Yaacob, a research fellow at the Lowy Institute’s Southeast Asia Program, the U.S. is unlikely to widen the scope of the defense pact, as doing so could draw them into a wider military conflict.

Philippine President Ferdinand Marcos Jr. said on Thursday that while the latest incident at the shoal was not an “armed attack,” the country needs to “do more” than protest China’s actions.

“The Philippines will continue to resupply the Sierra Madre, and hopefully invest in more outposts in their Exclusive Economic Zone in the South China Sea … There is no illusion that China will give up; what Manila is trying to do is not to give up on its own,” Paisentini said.

The Philippines defense chief has reiterated that the military would not announce its resupply missions to the shoal in advance. According to the Lowy Institute’s Yaacob, this could help it outmaneuver Beijing while avoiding direct confrontations.

The country has also been working to bolster its own defense capabilities in the South China Sea with the support of the U.S.

It also wants to prevent the U.S. from using the Philippines as a critical part of the “first island chain”- a chain of islands encompassing portions of Japan, Taiwan, the Philippines and Indonesia- seen as strategically important to contain the reach of the PLA, said researcher Muhammad Faizal.

The research fellow at Singpore-based S. Rajaratnam School of International Studies added that “every ally and partner is probably watching how committed the U.S. really is to its military alliances and planning ahead if the commitment falters.”