The Philippines has accused China's Coast Guard of launching a "brutal assault" with bladed weapons during a South China Sea clash earlier this week, a major escalation in a festering dispute that threatens to drag the United States into another global conflict.
Footage released by the Philippine military on Thursday showed Chinese coast guard officers brandishing an axe and other bladed or pointed tools at the Filipino soldiers and slashing their rubber boat, in what Manila called "a brazen act of aggression."
The Philippines and China have blamed each other for the confrontation near Second Thomas Shoal in the contested Spratly Islands on Monday, which took place during a Philippine mission to resupply its marines stationed on a beached World War II-era warship that asserts Manila's territorial claims over the atoll.
The incident is the latest in a series of increasingly fraught confrontations in the resource-rich and strategically important waterway.
But the scenes captured in the latest footage mark an inflection point in the long-simmering tensions, with China adopting new, far more openly aggressive tactics that, analysts say, appear calculated to test how the Philippines and its key defense ally – the United States – will respond.
Collin Koh, research fellow at the S. Rajaratnam School of International Studies in Singapore, said it was unprecedented for China's maritime law enforcement to board a Philippine naval vessel.
"They can be rubber boats, but it doesn't change the fact that they are Philippine Navy vessels, and according to international law, they enjoy what we term as sovereign immunity," Koh said. "That is very dangerous, because, if anything, that could even be construed as an act of war."
At a news conference on Wednesday, senior Philippine military officials said China's Coast Guard officers "illegally boarded" the Philippine rubber boats, "looted" seven disassembled rifles stored in gun cases, "destroyed" outboard motor, communication and navigation equipment and took the personal cellphones of Filipino personnel.
A Philippine Navy serviceman on the rubber boat lost his right thumb when the China Coast Guard rammed it, said Alfonso Torres Jr., commander of the Armed Forces of the Philippines (AFP) Western Command.
"Only pirates do this. Only pirates board, steal, and destroy ships, equipment, and belongings," Gen. Romeo Brawner Jr, chief of staff of the Armed Forces of the Philippines, said in a statement.
What happens in the South China Sea has profound implications for the US, which has a mutual defense treaty with the Philippines. Signed in 1951, the treaty stipulates both sides would help defend each other if either were attacked by a third party.
Derek Grossman, a senior defense analyst at the RAND Corporation, a US-based think tank, said the footage released by the Philippines "clearly shows a Chinese attack on Philippine military assets," which according to Washington and Manila's defense pact would trigger mutual defense commitments.
"However, in practical terms, the Philippines itself would have to initiate a move to activate (it) before the US would intervene militarily," he said.
Koh said China was trying to test both Manila and Washington "to find out exactly where the red line is."
"They wanted to see how far the US is willing to pledge its security commitment to the Filipinos. And of course, I don't think Beijing is dumb enough not to have considered the possibility of having all these actions escalate the situation, but I believe that was a risk that they, in the end, decided to take."
Keep reading about the implications.
More on tensions in the South China Sea: