China had advanced into a new phase in its gray zone tactic in the West Philippine Sea with the deployment of long-range acoustic devices, or LRAD, which are used in crowd control.

The utilization of the new weapon can be considered an escalation of the maritime conflict since experts on military gadgets said LRAD can cause permanent hearing impairment.

The weapon has been unwrapped for the Christmas convoy of about 30 civilian ships that set sail toward Ayungin Shoal.

Unfortunately, the three Bureau of Fisheries and Aquatic Resources, or BFAR, vessels — BRP Datu Sanday, BRP Bankaw and BRP Datu Tamblot — became the practice target or were mistaken as part of the civilian convoy.

BFAR sent the vessels to assist fishermen near Scarborough Shoal as part of a government program when they came under fire from Chinese water cannons at least eight times on Saturday.

Militia vessels then used the LRAD, which caused "severe, temporary discomfort and the incapacitation to some Filipino crew," according to a statement of the Task Force on the West Philippine Sea.

The assault also caused "significant damage" to the communication and navigation equipment of one of the three BFAR ships, Filipino officials said.

China's use of increasingly sophisticated means in its gray zone maneuvers translates to the strategy of the Philippines in engaging the Asian giant as succeeding.

Beijing has earlier shone a military-grade laser against a Philippine Coast Guard ship and much later conducted dangerous maneuvers near local vessels, and most recently, intentionally rammed resupply and escorting ships.

China is resorting to aggressive tactics that remain below the level of armed engagement and prevent triggering Article V of the Mutual Defense Treaty.

That portion of the treaty stated: "An armed attack on either of the Parties is deemed to include an armed attack on the metropolitan territory of either of the Parties or on the island territories under its jurisdiction in the Pacific or on its armed forces, public vessels or aircraft [emphasis added] in the Pacific."

Regional experts said the People's Liberation Army, unlike in previous years, now has both the capability and capacity to harass rival vessels, especially as supported by artificial island construction and militarization of nearby features, including Mischief Reef, Subi Reef and Fiery Cross Reef in the Spratly Islands.

So far, the US-Philippine alliance has succeeded in deterring an armed attack, but regional experts warned Beijing's intensifying efforts to leverage gray-zone tactics is nevertheless a cause for concern.

According to Derek Grossman, a senior defense analyst at the think tank RAND Corp, China could cross the line, whether purposefully or inadvertently, that would trigger the Mutual Defense Treaty and lead to war.

He said China is rolling out new and creative gray-zone tactics to get the point across, "only reconfirm the fact that deterrence through the strengthening US-Philippine alliance is working."

"Because deterrence is holding, Beijing must reach into its toolkit to find additional coercive gray-zone tactics to stop future resupply missions, short of an armed attack," Grossman added.

He assessed, "Rather than view such moves with frustration, Manila and Washington should consider them a victory."

Grossman worries that the skirmishes may result in an accident at sea that could lead to miscalculation, escalation, and armed conflict.

"This is the scenario that understandably keeps American and Philippine policymakers and strategic planners up at night. As my colleague Blake Herzinger recently argued, one way of mitigating the potential risk is to remove the Sierra Madre and replace it with a combined forward operating base that includes Philippine forces and US Marine Corps," the analyst said.

He added that such a base could significantly bolster deterrence because the US Navy is much better at repelling Chinese gray-zone activities.

A tradeoff for a base build-up, however, would be inviting reprisals from an increasingly assertive China.

So long as the sovereign entitlement is protected, deterrence should be the response to aggressiveness.