The US has been putting increased pressure on the Chinese maritime militia, a paramilitary sea force disguised as a fishing fleet, in an effort to deter provocations in the South China Sea.

The US Navy's top admiral told his Chinese counterpart earlier this year that provocations by militia vessels would be treated the same as those carried out by Chinese navy warships.

Last week, the US ambassador to the Philippines told reporters that US defense obligations to its ally could be triggered by maritime militia attacks.

Troubling incidents involving Chinese fishing vessels are not uncommon in the South China Sea, and while this rhetorical shift in the US position could deter aggression to encourage stability, it could also signal a lower threshold for confrontation and, possibly, conflict in the disputed waterway.

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The US has been steadily ratcheting up the pressure on China's sea forces in a way that could lower the threshold for conflict in the South China Sea, which is already a hotbed of tension.

The US is signaling a tougher stance toward the Chinese maritime militia, a paramilitary sea force disguised as a fishing fleet that is known to sometimes harass foreign rivals to enforce China's vast sovereignty claims in the contested waterway.

The Chinese maritime militia "thrives within the shadows of plausible deniability," according to Andrew Erickson, a leading expert at the US Naval War College, but it can no longer hide like it once could.

The Department of Defense first called attention to the maritime militia in its 2017 report on China's military power. The report said China uses its commercial fishing fleet to engage in gray-zone aggression, "enforce maritime claims and advance its interests in ways that are calculated to fall below the threshold of provoking conflict."

It wasn't until this year, though, that the US really began putting pressure on the militia forces.

Chief of Naval Operations Adm. John Richardson warned his Chinese counterpart during a meeting in Beijing in January that the US Navy would treat coast-guard and maritime-militia vessels as combatants and respond to provocations the same way it would a Chinese navy ship, the Financial Times reported.

In March, Secretary of State Mike Pompeo publicly assured the Philippines that the US would come to its defense in the event that it was attacked in the South China Sea.

"Any armed attack," he said, "on Philippine forces, aircraft or public vessels in the South China Sea will trigger mutual defense obligations."

Sung Kim, the US ambassador to the Philippines, clarified the earlier assurances on Friday, telling reporters that US security guarantees apply to acts of aggression by the Chinese maritime militia.

"Any armed attack, I would think that would include government-sanctioned militias," the ambassador said, according to The Philippine Star. He did not say what type of behavior would constitute an "armed attack."



The increased pressure is intended to change China's strategic calculus in the disputed waterway, experts say.

"By injecting greater uncertainty about how the US will respond to China's grey-zone coercion," Bonnie Glaser, a China expert at the Center for Strategic and International Studies, told the Financial Times, "the US hopes to deter Chinese destabilizing maritime behaviour, including its reliance on coast guard and maritime militia vessels to intimidate its smaller neighbours."

The US position could lead to increased stability by deterring provocation. At the same time, it potentially makes it easier for a lower-level dispute between China and its neighbors to escalate, especially considering the ambiguity surrounding both the US deterrence posture and the role of the maritime militia.

Incidents involving Chinese fishing vessels, potential members of the maritime militia, are frequent occurrences in the South China Sea. It is unclear exactly what kind of incident might trigger US defense obligations.

For instance, in April, more than 200 Chinese fishing vessels were accused of swarming Thitu Island, a Philippine-occupied territory in the Spratly Islands.

And, last week, a suspected Chinese vessel was accused of ramming a Philippine ship in the South China Sea, sinking it, and then sailing off as nearly two dozen Filipino fishermen fought for their lives in open water.

China has denied allegations of misconduct. And, while tensions persist, Philippine leadership has notably called for calm, indicating that escalation is unlikely at this point in time.