The Future of Defense Cooperation and Regional Security Challenges: Lessons From the Philippines

The Philippines occupies an unusual position in the strategic geometry of the Indo-Pacific. It is neither a great power nor a marginal actor, but a maritime state whose geography places it directly along the region’s principal fault lines—from the South China Sea to the Taiwan Strait and the broader First Island Chain. For Manila, the core strategic question is not whether it can compete with stronger powers militarily—it cannot and will not—but how a treaty ally with limited hard power can leverage alliances, legal norms, and emerging security networks to enhance deterrence while preserving strategic autonomy.

This dilemma has become sharper as the Indo-Pacific security architecture undergoes a fundamental transformation. For decades, stability in the region rested on a hierarchical structure centered on the United States. The so-called San Francisco System—often described as the hub-and-spokes alliance model—linked Washington to individual allies such as Japan, South Korea, Australia, and the Philippines through bilateral treaties. That system remains intact, but it is no longer the sole organizing principle of regional security. Instead, it is gradually evolving into a more complex, layered, and networked architecture. In this emerging system, the United States increasingly acts as a facilitator of interlocking partnerships rather than the sole anchor of regional order. Security cooperation is now structured less like a hub and more like a web—composed of overlapping coalitions, trilateral arrangements, and functional minilateral initiatives that address specific threats.

The Philippines is an important case study in how smaller and middle powers can adapt to this new environment. Its experience demonstrates how states with limited military capabilities can strengthen deterrence not through sheer force, but through strategic networking, asymmetric defense investments, and legal and normative leverage.

A Destiny Defined by Geography

Philippine defense policy begins with geography. The country is an archipelago of more than 7,600 islands with a coastline exceeding 36,000 kilometers. Its maritime domain covers roughly 2.2 million square kilometers, including an exclusive economic zone extending 200 nautical miles from its shores. Such spatial dispersion creates extraordinary logistical challenges for defense planning. Protecting territorial waters, maritime resources, and critical sea lines of communication requires constant surveillance across a vast and fragmented seascape.

This geographic reality also ties national security directly to economic survival. Maritime trade routes sustain the Philippine economy, while offshore energy resources play a crucial role in domestic energy supply. The Malampaya gas field, located northwest of Palawan, has long provided roughly one-third of the electricity for Luzon, the country’s main island. As the field approaches depletion, attention has increasingly shifted to potential reserves in contested areas of the South China Sea, particularly Reed Bank. Ensuring access to these resources has therefore become a strategic priority.

Yet, geography also exposes the Philippines to persistent maritime pressure. Chinese coast guard vessels, maritime militia units, and survey ships regularly challenge Manila’s exclusive economic zone. These activities are typically framed by Beijing as routine law enforcement or civilian operations, but they form part of a broader pattern of coercive activities designed to expand territorial control and wear Manila down without triggering open armed conflict. For the Philippines, this environment underscores a structural reality: deterrence must operate below the threshold of conventional warfare.

Archipelagic Defense as the New Challenge

The Armed Forces of the Philippines focused primarily on internal security for much of the post-Cold War period. Counterinsurgency campaigns against communist rebels and Islamist militant groups dominated military planning and resource allocation. External defense capabilities received relatively little investment.

This orientation is now changing. As insurgent groups have weakened, Manila has begun shifting its military posture toward territorial and maritime defense. Counterinsurgency operations now account for only a small portion of the armed forces’ overall mission. The central strategic framework guiding this transition is the Comprehensive Archipelagic Defense Concept (CADC), which emphasizes protecting the country’s maritime approaches and key chokepoints rather than relying on a traditional land-based defense posture.

The shift requires significant modernization. Under the Armed Forces’ Re-Horizon 3 program, Manila has approved approximately $35 billion in defense spending over a ten-year period. The modernization plan focuses on acquiring capabilities that enhance deterrence at sea and in the air, including missile systems, surveillance networks, and eventually diesel-electric submarines. The Philippines does not aim to match larger powers ship-for-ship or aircraft-for-aircraft. Instead, it is investing in asymmetric capabilities designed to complicate an adversary’s ability to operate freely in contested waters. One example is the acquisition of the BrahMos supersonic cruise missile system from India. With a range approaching 300 kilometers, shore-based batteries deployed along key coastal areas can threaten hostile vessels operating near Philippine waters. Even a small number of such systems can significantly alter the strategic calculus by increasing the risks faced by potential adversaries.

Deterrence in the Philippine context therefore rests increasingly on denial rather than punishment. The goal is not to defeat a larger power outright but to make coercive actions costly, uncertain, and operationally difficult.

Same Risks, Different Philippines: An Alliance Reimagined

These military developments unfold alongside a significant evolution in the U.S.–Philippines alliance. The two countries signed the Mutual Defense Treaty in 1951, but for decades the alliance functioned largely as a traditional patron-client relationship. The United States provided security guarantees and military assistance, while Manila hosted U.S. bases and aligned with Washington’s strategic priorities. This dynamic is gradually shifting toward a more reciprocal partnership. Updated Bilateral Defense Guidelines issued in 2023 clarified that the Mutual Defense Treaty applies to armed attacks on Philippine forces anywhere in the South China Sea and explicitly includes coast guard vessels. This clarification closes an ambiguity that previously allowed gray-zone tactics to operate in the space between law enforcement and armed conflict.

Operational cooperation has expanded as well. Under the Enhanced Defense Cooperation Agreement (EDCA), the United States now has access to nine military sites across the Philippines. Several of the newer locations are situated in northern Luzon and Palawan—positions that provide proximity both to contested areas of the South China Sea and to the Taiwan Strait. These sites support joint training, prepositioning of equipment, and rapid humanitarian response capabilities. Such integration strengthens deterrence but also introduces strategic risks. Greater interoperability and rotational deployments enhance the credibility of extended deterrence, yet they also raise concerns about entrapment. Manila must manage the possibility that tensions involving the United States and China—particularly around Taiwan—could escalate in ways that draw the Philippines into a broader conflict.

To mitigate these risks, Philippine policymakers have pursued several activities that combine alliance strengthening with diplomatic diversification and narrative control. One notable example is the transparency initiative of the Philippine Coast Guard. Incidents involving Chinese vessels in disputed waters are carefully documented and publicly released to international audiences. The aim is to shape global perceptions of maritime behavior and to frame Philippine actions within the language of international law and rules-based order. This alone, however, is not sufficient to deter China.

The Rise of Security Networks in Southeast Asia

Beyond its alliance with Washington, Manila has increasingly embraced minilateral cooperation—small, flexible groupings of states that coordinate on specific security issues. This trend reflects broader changes across the Indo-Pacific. Large multilateral institutions often struggle to respond quickly to security crises. ASEAN, for instance, operates through consensus-based decision-making, which makes unified responses to sensitive geopolitical issues difficult. As a result, many states have turned toward smaller coalitions that can act more efficiently.

The Indo-Pacific now hosts a growing ecosystem of such arrangements. The Quadrilateral Security Dialogue links Australia, India, Japan, and the United States, and the AUKUS partnership between Australia, the United Kingdom, and the United States is another. These frameworks are not formal alliances but functional mechanisms for cooperation in areas such as technology sharing, maritime security, and defense innovation.

The Philippines has begun latching on to this emerging networked environment. One important development is the Reciprocal Access Agreement between Japan and the Philippines, which entered into force in 2025. The agreement establishes legal and logistical procedures for military forces from each country to operate in the other’s territory. It enables joint exercises, training activities, and logistical cooperation independent of—but complementary to—their respective alliances with the United States. Similarly, trilateral maritime cooperation among Japan, the Philippines, and the United States has expanded through coordinated patrols and exercises. Manila has also conducted joint maritime activities with Australia, Canada, and New Zealand. These engagements help improve interoperability and maritime domain awareness while signaling collective commitment to maintaining freedom of navigation.

Importantly, such arrangements do not represent the formation of an “Asian NATO.” They remain flexible, issue-specific, and largely operational rather than institutional. Their purpose is to provide practical mechanisms for cooperation without imposing rigid alliance commitments that could constrain regional diplomacy.

Lessons from the Philippines’ Experience

Several broader lessons emerge from the Philippine case.

1. Credible deterrence for smaller powers often depends on denial rather than dominance. Investments in coastal defense systems, surveillance networks, and precision strike capabilities can create significant operational challenges for stronger adversaries. Even modest military assets can reshape the strategic environment when deployed intelligently across key maritime chokepoints.
2. Security cooperation is becoming increasingly networked. Traditional bilateral alliances remain important, but they are now complemented by trilateral and minilateral arrangements that enable flexible, issue-specific collaboration. These frameworks allow states to coordinate responses to emerging threats without the institutional rigidity of large multilateral organizations.
3. Legal and normative strategies remain powerful tools, but these alone are not sufficient. The Philippines’ successful arbitration case against China in 2016 established an important legal benchmark under international law. Although enforcement remains difficult, the ruling provides diplomatic leverage and reinforces Manila’s narrative that its actions align with the rules-based international order.
4. Defense modernization must include technological and industrial dimensions, and an economic buy-in to incentivize private sector participation. Recognizing this, the Philippines has introduced legislations—such as the CREATE Law, Self-Reliant Defense Posture Revitalization Law, Strategic Trade Management Law, “re-Horizoned” AFP Modernization, and the revised Government Procurement Law, among others—aimed at strengthening its domestic defense industry through incentives for technology transfer, local production, and maintenance capabilities. Developing even a limited domestic defense ecosystem can enhance strategic autonomy and reduce reliance on external suppliers that supports the Philippines’ agential role as contributor to the alliance.
5. Effective strategy requires balancing alliance commitments with sovereign agency. The United States remains the Philippines’ most important security partner, yet overreliance on any single external power can create vulnerabilities. Diversifying defense relationships—with partners such as Japan, Australia, South Korea, Canada, and European states—helps ensure that Manila retains diplomatic flexibility while allowing space for broader cooperation and amid shifting geopolitical conditions.

A Networked Future?

The future of Indo-Pacific security will likely be defined less by rigid blocs than by adaptive networks of cooperation. The Philippines’ evolving strategy reflects this reality. By combining asymmetric defense investments, alliance modernization, and participation in minilateral security initiatives, Manila is attempting to transform structural weakness into strategic leverage. This approach does not eliminate the risks inherent in great-power rivalry. The Philippines remains exposed to maritime coercion, regional instability, and the possibility of escalation between larger powers. But its experience illustrates how smaller states can navigate these pressures through creative diplomacy and networking without sacrificing agency and core strategic priorities.

In a region increasingly shaped by competition and uncertainty, the Philippine case offers a broader insight: influence in the international system is no longer determined solely by military strength. It also depends on how effectively states connect themselves to the emerging web of partnerships that now defines the Indo-Pacific security landscape.

The views expressed are solely the author’s and do not reflect those of Perry World House, the University of Pennsylvania, or Carnegie Corporation of New York.