The Trump Administration’s recently released November 2025 National Security Strategy of the United States revived the mid-20th-century geopolitical concept of the strategic relevance of the first island chain. The said document stated: “We will build a military capable of denying aggression anywhere in the First Island Chain. However, the American military cannot, and should not, have to do this alone. Our allies must step up and spend—and more importantly do—
much more for collective defense.” The first-island chain is the geopolitical linear arrangement of three major island groups: Japan’s Southwest Islands, Taiwan, and the Philippine archipelago. The concept of a first-island chain is based on a traditional geopolitical assumption that occupying and controlling this collection of islands provides locational advantages, triggering undeniable attractions from great naval powers, drawing them in through a small island's "suction effect" (SISE).
In recent times, driven by its vast economy and expanding navy, Beijing has pursued a policy of maritime expansionism that challenges Washington’s pivotal position in the first-island chain, extending from Japan to Taiwan and the Philippines. Projecting its growing comprehensive power eastward, China seeks to break past the first island chain, namely Japan’s Southwest Island chain, Taiwan, and the Philippines, into the open waters of the Western and Central Pacific. This, consequently, is leading to a 21st-century version of the mid-20th-century Cold War First Island Chain Strategy.
Reviving a 21st Century Island-Chain Strategy
Washington conceived the first island chain strategy during the Cold War to contain the Soviet Union and China. It provided for establishing American naval and air bases in the Western Pacific, from which to project American air and naval power and deny access to Soviet and Chinese expansion into the Central Pacific. In the context of the 21st century, the strategy involves linking the defense postures of the Philippines, Taiwan, and Japan through security partnerships among the three. Three significant developments are creating the necessary conditions for the formation of a first island chain strategy that can constrain Chinese maritime expansion. They are: the Philippines’ adoption of a Comprehensive Archipelagic Defense Concept (CADC), the enhancement of the Philippine-Japan security partnership, and the growing realization by Manila and Tokyo that they need to link their security relations with Taipei, despite their respective One-China policies.
The Philippines’ Archipelagic Defense Concept (CADC)
In January 2024, Philippine Secretary of National Defense Gilberto Teodoro announced a new defense concept known as the “Comprehensive Archipelagic Defense Concept” (CADC). The CADC requires the Armed Forces of the Philippines (AFP) to create a credible defensive posture to build the country’s deterrent capabilities in the Philippines' archipelagic waters and EEZ. The CADC aims to rectify the Philippines’ strategic vulnerabilities and enhance the AFP’s capability to protect national interests through long-term plans. The CADC is designed to enable the AFP to project its capabilities into maritime areas of the country that require protection and preservation. The Philippine military must boost its maritime situational awareness, connectivity, intelligence capabilities (C41STAR), and area-denial and deterrence capabilities in marine and aerial domains. The AFP must also adopt a new strategic paradigm, driven by the urgency to develop its anti-access and area denial capabilities. This also requires the AFP to develop strategic bases around the fringes of the Philippine archipelago. These measures are designed to prevent other militaries from operating or crossing the vast stretches of its archipelagic territory, with the stated goal of making its EEZ in the West Philippine Sea/South China Sea a no-go zone of the Chinese maritime militia, China Coast Guard (CCG), and People’s Liberation Army Navy (PLAN).
By implication, this means the AFP is moving away from its old concept of defending the country’s long and rugged coastal areas. This required the Philippine military to anticipate an invading force moving toward the country’s shoreline before mounting any combat operation against this amphibious enemy. Instead, the AFP is formulating a new strategic paradigm based on the need to bolster its anti-access and area denial capabilities within the Philippines’ archipelagic territories, including the country’s EEZ. This also required the AFP to develop defense capabilities and utilize resources to establish a credible deterrent posture or forward defense that covers the country’s exclusive economic zone (EEZ). These capabilities are intended to prevent other militaries from operating or crossing the vast stretches of its archipelagic territory, with the stated goal of making its EEZ in the West Philippine Sea/South China Sea a no-go zone for the Chinese maritime militia, CCG, and PLAN. More significantly, implementing CADC would effectively enable the Philippines to fill the strategic vacuum in the southern flank of the First Island Chain.
The Enhancement of Philippine-Japan Security Partnership through JAPHUS
In recent times, Tokyo and Washington have expanded their alliance relationship, especially in the maritime security domain, by including a third party. The U.S. and Japan have enhanced their collective defense capabilities through consultations and involvement with other Indo-Pacific countries, including Australia, India, and South Korea. From 2023 to 2024, Tokyo and Washington decided to engage Manila strategically. This led the Kishida Administration to focus on enhancing Japan’s strategic partnership with the Philippines. On April 11, 2024, Presidents Ferdinand Marcos of the Philippines and Joe Biden of the United States, along with Prime Minister Fumio Kishida of Japan, convened in Washington, D.C. to meet for the first summit of the Japan-Philippine-U.S. (JAPHUS) Trilateral Security Partnership.
With Japan and the U.S. strengthening their respective security relations with the Philippines, the three countries have worked to bring each other closer to deep and comprehensive trilateral security cooperation, building up what can be considered a collective capacity to address common regional security concerns. Japan, the Philippines, and the U.S. are intensifying their security partnership through the JAPHUS defense network. This security network is formed by a strengthened alliance between Tokyo and Washington, with both allies strengthening the foundations of their strategic partnerships with Manila. Consequently, JAPHIS’s informal and de facto trilateral security network is intact and active, generating appreciable results after its formation in April 2024. These benefits include:
1) Through JAPHUS, the U.S. and Japanese security assistance and guarantee to the Philippines have strengthened its resolve to confront Chinese gray zone operations in the South China Sea.
2) Through Japan’s participation in the trilateral security partnership, Tokyo has extended security assistance to the AFP modernization program by providing radar and other non-lethal military hardware.
3) Through this trilateral security arrangement, Japan and the U.S. have synchronized their security assistance to the Philippines by aligning their efforts to support the Philippines’ defense priorities in implementing the CADC. For example, the installation of Japanese-made air-surveillance systems at Wallace Air Station, and the U.S. continued development and integration of the Philippine Air Force (PAF) air domain sensors at the Basa Air Base Command and Control Fusion Center, have collectively helped develop the AFP’s air and sea domain-awareness capabilities in its archipelagic waters.
4) Through JAPHUS, the Japan Self-Defense Force (JSDF), the AFP, and the U.S. Armed Forces have enhanced operational coordination and interoperability by periodically conducting multilateral maritime cooperative activities in the South and East China Seas. Through these activities, the AFP, the JSDF, and the U.S. Armed Forces have agreed to explore joint planning for intelligence, surveillance, and reconnaissance activities to enhance interoperability and coordination in effective maritime and air domain awareness in the East China Sea, South China Sea, and surrounding waters.
The Recognition of the Need to Establish Security Relations with Taiwan
In the recent past, Manila and Tokyo have been less vocal about their security concerns about China’s plan for an armed unification against Taiwan because of their respective One-China Policy. However, there is a growing realization in the two capitals that if China controls and dominates the South China Sea and Taiwan, Beijing can tilt the balance of power in its favor. China will then exercise effective sea control over the region’s sea lanes of communications (SLOCS) and effectively prevent the U.S. 7th Fleet from operating within the waters of the first-island-chain. Hence, aside from ensuring that no single power controls and dominates the South China Sea, it is also in Manila's and Tokyo’s interest to ensure that Taipei remains a strategic buffer against Beijing’s goal to dominate the first island chain. This led to both Manila and Tokyo expressing their mutual concerns about China’s irredentist agenda regarding Taiwan, despite their adherence to the One-China policy.
Recently, the Marcos Administration has become more articulate about the need for the Philippines to prepare for a Taiwan contingency. In August 2025, during President Marcos Jr.’s first official visit to India, he publicly mentioned what many defense officials, analysts, and military officers are discussing in several closed-door defense and security conferences in the Philippines: “If there is an all-out war, we will be drawn into it. We will have to go into Taiwan and bring our people home.” Firstpost Managing Editor Palki Sharma hosted this question during an interview about how the Philippines will respond in a Taiwan contingency. President Marcos added that his country “cannot stay out if a conflict breaks out between China and Taiwan,” as the Philippines would be “drawn into it to protect its citizens working in Taiwan.” A few days later, after his return to Manila, he reiterated what he stated in Delhi: “To be practical about it, if there is confrontation over Taiwan between China and the United States, there is no way that the Philippines can stay out of it because of our geographical location.” President Marcos reiterated this statement in response to the Chinese Foreign Ministry’s harsh and critical condemnation of his remarks regarding the Philippines' potential response in the event of a contingency involving Taiwan.
Tokyo has also been vocal about its need to prepare and respond to a Taiwan Contingency. In the past, Japanese prime ministers have refrained from answering hypothetical questions on a Taiwan emergency and contingency. However, this changed in November 2025 when Prime Minister Sanae Takaichi’s recent statement hinting that a Chinese naval blockade in the vicinity of Taiwan could constitute a ‘survival-threatening situation—potentially triggering the mobilization of the Self-Defense Forces—that has recently triggered a major Sino-Japanese diplomatic row.
A Japanese-led First Island Chain Mini-lateral?
The first step in forming this island defense system is for the three to establish a security partnership among themselves. Japan and the Philippines have already linked their respective defense policies through the 2015 Philippine-Japan Strategic Partnership, known as JAPHUS, and more recently, the Philippine-Japan Reciprocal Access Agreement (RAA) of 2025. Both the Philippines and Japan, despite their One-China policy, must pursue an informal security partnership with Taiwan. As the most powerful among the first island chain countries, Japan must take the lead in forming a First Island Chain mini lateral. To form this fist-island chain mini-lateral, Manila, Taipei, and Tokyo should consider the following measures:
1) Japan, Taiwan, and the Philippines should view their respective long-term strategic interests as closely linked and inviolable.
2) Manila, Taipei, and Tokyo should hold several informal and track 2 dialogues regarding the inviolability of their security interests and the need to link their defense policies despite the Philippines and Japan’s One-China Policies.
3) The Philippines and Japan should enhance their comprehensive security partnerships through joint military exercises and maritime cooperative activities, Subject Matter Exchanges (SME) exchanges, transfer of Japanese Excess Defense Articles to the Philippines, and mutual logistic arrangements.
4) Despite the Philippines’ strict and highly legalistic One-China Policy, Manila and Taiwan should explore an informal defense cooperation through intelligence exchanges, security and defense dialogues between ranking AFP and Taiwan Armed Forces, SME exchange, joint military exercises in third countries, and maritime cooperative activities at the Luzon Straits and the Philippine Sea.
5) Japan, Taiwan, and the Philippines should strengthen their respective security relations with their common security ally and partner, the United States.
6) The AFP, the JSDF, and the Taiwan armed forces should encourage the U.S. Indo-Pacific Command (USINDOPACOM) to host military exercises and command conferences at Guam and Hawaii, where units from the AFP, the Taiwan armed forces, and the JSDF can join and participate.