President Marcos on Monday, April 15, made it clear that if any Filipino serviceman would be killed in an attack in the West Philippine Sea, the United States would step in to defend the Philippines.

As gray zone operations—or activities that fall short of being called as war—continue in the waters still contested by China, Marcos finally said what would invoke the Philippines' Mutual Defense Treaty (MDT) with the Philippines.

"I think (US Defense) Secretary (Lloyd) Austin explained it very well. If any servicemen, Filipino service man, is killed by an attack from any foreign power, then that is time to invoke the Mutual Defense Treaty," the President said during a presidential forum with the Foreign Correspondents Association of the Philippines (FOCAP).

Marcos recently flew to the US for a trilateral summit with US President Joe Biden and Japanese Prime Minister Fumio Kishida to talk about developments in the South China Sea. He also met with Austin, who reaffirmed Washington's defense commitment with Manila.

"As long as they have actually caused casualties, and it has killed the serviceman... whatever their designation are, whether they're merchant marine or Coast Guard or actual...navy vessels, it does not matter," he added.

The President also said that the defense treaty would be invoked if the attack would be perpetrated either by a foreign military or a foreign militia.
The defense chiefs of the Philippines and the US had already "condemned" China's gray zone in the South China Sea as they said these acts interfere with the livelihood of Filipino fisherfolk.

In a readout provided by the US Department of Defense following a phone call between Austin and his Filipino counterpart, Carlito Galvez, in March 2023, the two officials already called out Beijing for its activities that impede the rights of other claimant states "that seek to operate lawfully in the South China Sea consistent with the 2016 Arbitral Tribunal ruling."

Austin and Galvez noted "with particular concern" the Chinese aggression in the waters when it deployed dozens of its vessels, including a People's Liberation Army Navy ship, to the waters off the Philippine-administered Pag-asa (Thitu) Island, as well as when it conducted dangerous maneuvers, water cannon attack and pointing military grade laser.

Various experts had also come together to call on the Philippine government and the public to counter China's operations.

Former German Ambassador to the Philippines Anke Reiffenstuel already warned against the gray zone operations in the South China Sea through non-military means in a bid to assert one's territorial claims.

For Reiffenstuel, such activities undermine international law and "pose a significant threat to regional security and stability."

And since these actions "are mostly below the threshold of military conflict," she said "adequate and yet balanced response is challenging."