By Shirin Bhandari | 2025-07-22

In a significant shift in defense posture, the Philippines is adopting Japan's "one-theater" concept -- an integrated approach that treats the East and South China Seas as a single strategic zone of military operations.

The concept, proposed in 2024 by then-Japanese Defense Minister Gen Nakatani, urged the United States to consider the East China Sea, South China Sea, the Korean peninsula and surrounding areas as a unified theater.

Japan's Joint Operations Command has since implemented this framework, with Manila aligning accordingly.

Philippine Defense Secretary Gilberto Teodoro announced during a briefing that it was "reasonable" to treat both seas as one operational space because both are maritime areas with no land borders involved, Reuters reported June 30.

Teodoro said that the concept is already in motion and does not require new treaties, having been approved by relevant military hierarchies.

The shift will involve a broad transformation of the Philippine defense posture, he added.

"That will involve synergy in operations, synergy in domain awareness, in intelligence exchange, and in mutually reinforcing our strengths to work doubly real-time," he explained.

The armed forces, under Chief of Staff Gen. Romeo Brawner Jr., are now adapting the concept, with future oversight expected to transition to the newly established Strategic Defense Command.

Countering China

The move signals Manila's determination to counter China's maritime coercion and deepen military coordination with allies including Japan, the United States and Australia.

It comes as Manila faces mounting tensions with Beijing in the West Philippine Sea.

Chinese coast guard and maritime militia vessels have repeatedly obstructed Philippine resupply missions and patrols, particularly near Second Thomas Shoal and Scarborough Shoal.

Meanwhile, Japan faces similar confrontations with China in the East China Sea over the Senkaku Islands and exclusive economic zone boundaries. These shared experiences have brought the Philippines and Japan into closer strategic alignment.

This convergence is visible in the evolving structure of Manila's defense alliances.

Over the past two years, the Philippines has emerged as a central hub for regional maritime cooperation with Australia, Japan, South Korea and the United States.

It maintains Visiting Forces Agreements with Australia, Japan and the United States, allowing for expedited troop deployments and joint training.

At the logistical level, Manila and Tokyo signed an Acquisition and Cross-Servicing Agreement in April, enabling them to share fuel, ammunition and supplies during operations.

While the Philippines already has a military intelligence-sharing agreement with Washington, officials and analysts have called for similar arrangements with Tokyo and Canberra to support seamless coordination under the one-theater model.

To anchor the operational side of this evolving alliance network, a Combined Coordinating Center (CCC) is slated to open in Manila by December.

The CCC will function as the strategic nerve center for the so-called "Squad" nations -- the United States, Japan, the Philippines and Australia -- facilitating joint planning, surveillance and response protocols across contested waters.

The project reflects growing consensus on the need for structured, institutionalized cooperation amid escalating regional risks.

Growing cooperation

While strategic integration is the centerpiece, defense hardware plays a supporting role. Japan has agreed to transfer six Abukuma-class destroyers to the Philippines, the Yomiuri Shimbun reported July 6.

The ships, launched between 1989 and 1993 for antisubmarine and escort missions, mark the first such export under Tokyo's defense equipment transfer policy.

These vessels, which are 109 meters long, have a displacement of 2,550 tons each and can accommodate about 120 personnel, are being retrofitted for Philippine navy use as they are slowly being decommissioned because of their aging systems, according to the Yomiuri Shimbun.

A joint inspection of the vessels is scheduled for August, with formal transfer expected in 2027.

The addition of these destroyers will significantly expand the Philippine navy's patrol potential. Even though they are aging, they will boost the navy's capabilities, which currently rely on just two operational frigates compared to China's 100-plus surface ships.

This acquisition is part of Manila's broader naval modernization plan, which also includes recent procurements from South Korea and Israel.

Integrated security efforts

While the Philippines, Japan and the United States have signaled alignment on the one-theater concept, countries like South Korea and Australia are more cautious.

Seoul remains primarily focused on North Korea, and under President Lee Jae-myung, it has taken a stance more equidistant from Washington and Beijing.

In Australia, some policymakers see a potential Chinese invasion of Taiwan as geographically limited, which may hinder Canberra's engagement in broader Western Pacific operations.

Still, despite these complications, the operationalization of a one-theater model appears increasingly likely among its core supporters. For Manila and Tokyo, the concept offers a framework not just for managing crises but for deterring them.

"From a general standpoint, the challenges faced by these countries in the past two years alone should be enough reason to forge a more integrated and consistent response towards China's assertiveness in the maritime space," Don McLain Gill of De La Salle University in Manila wrote in Think China on July 16.

"At the very least, a robust partnership between the United States, Japan and the Philippines holds the most promise in operationalizing this one-theater framework for integrated security efforts," he said.