Vol.26. July 31. 2025

What is happening in East Asian Maritime Security? The Research Institute for Peace and Security (RIPS) publishes the biweekly newsletter, the information on maritime security relevant to East Asia and Japan's territory.

Monthly Column

Confronting China’s Maritime Expansion
in the South China Sea:
The July 12, 2016, UNCLOS Award
and the Marcos Administration’s
Comprehensive Archipelagic Defense Concept (CADC)

Renato Cruz De Castro

Distinguished Professor,
De La Salle University, Manila.

The South China Sea is the main arena of the People's Republic of China’s (PRC’s) integrated maritime campaign for Chinese expansion in the waters of the first-island chain.
China’s integrated maritime campaign for expansion seeks two objectives:
a) de facto—or the imposition of a state of affairs based on raw hard power and use of force;
b) de jure—earning the legal recognition of China’s sovereignty over the South China Sea through lawfare. China’s long-term objective is to gain de facto recognition and legitimacy for its unilateral and expansive territorial claims over the South China Sea’s vast marine terrain, several surface and subsurface land features, and natural resources above and below the seabed. It deploys its well-equipped and well-trained three maritime services in its expansionist and coercive naval campaign against the smaller littoral Southeast Asia states.
Beijing deploys the People’s Liberation Army’s Navy (PLAN), with its numerous and advanced naval vessels, to provide it with the escalatory option of the threat or actual use of force.
Beijing then sends the Chinese Coast Guard (CCG), which ensures the presence of civilian Chinese maritime forces in the South China Sea. Finally, it reinforces and complements Chinese naval and civilian forces with the People’s Armed Forces Maritime Militia (PAFMM), which is tasked with maintaining a persistent and ingenious presence in the contested maritime terrain of the South China Sea.

The PLAN, the CCG, and maritime militias are tasked to advance and foster China’s economic activities in the disputed waters. At the same time, they obstruct the Southeast Asian littoral states’ economic activities. The PLAN and the CCG cooperate to normalize their joint armed naval patrol activities to maintain and assert Chinese rights and interests in the South China Sea. However, if challenged by the littoral Southeast Asian states, China’s maritime services will decisively respond to crises involving these states’ smaller and weaker navies and coast guards.

Since 2011, the Philippines has challenged China’s maritime expansion in the South China Sea.
Lacking the necessary military capabilities, in January 2013, the Philippines filed a case in the Permanent Court of Arbitration (PCA). This was aimed at depriving China of the prospect that it could achieve the second goal of its integrated maritime expansion—earning the legitimacy of its expansive claim in the South China Sea.
In 2016, the Arbitral Tribunal on the United Nations Convention on the Law of the Sea (UNCLOS) determined that China’s basis for its expansive claim—the nine-dash line is an entirely untenable claim because it has no basis in international law.
The tribunal stated that since China became a party to the UNCLOS, it could not legally claim to exercise historic rights in areas beyond 12 nautical miles from its coast.
The tribunal explained that there was no evidence to support China’s landmark claim in the South China Sea. By ruling that China’s nine-dash line claim has no legal basis and, therefore, is groundless, on July 12, 2016, the tribunal effectively deprived China of the opportunity to exercise de jure jurisdiction over the South China Sea.

The UNCLOS Award as the CADC’s Basis
Even before he assumed the presidency, Mr. Ferdinand Marcos declared that he would assert the Philippines’ territorial rights over the West Philippine Sea.
He said he would negotiate with China consistently with a firm voice about the two countries’ territorial dispute. He also announced that he would use the July 2016 arbitral award against China’s expansive and sweeping claims in the South China Sea to assert his country’s territorial rights.

Since 2023, President Marcos has pursued a vigorous balancing policy based on the July 12, 2016, arbitral ruling to challenge China’s maritime expansion in the South
China Sea.
Specifically, this balancing policy entails building up the Armed Forces of the Philippines’ (AFP’s) territorial/external defense capabilities, enhancing its alliance with the U.S. by increasing American strategic presence in the Philippine territory, fostering security arrangements with other American allies like South Korea, Japan, and Australia, and, more recently, adopting the Comprehensive Archipelagic Defense Concept (CADC).

In January 2024, Secretary of National Defense Gilberto Teodoro announced the gist of CADC. CADC incorporates President Marcos’ view that China’s activities aimed to implement its 10-dash line claim in the South China Sea are not only a blatant disregard to the United Nations Convention on the Law of the Sea (UNCLOS) and to the July 12, 2016, Arbitral Tribunal Ruling. As an archipelagic state, they constitute a serious strategic threat to Philippine national security. It directs the AFP to build and project its naval and aerial capabilities up to Manila’s EEZ and develop and expand the country’s strategic depth to enhance the defense of the Philippines’ archipelagic territory.
CADC’s long-term goal is to guarantee the unimpeded and peaceful exploration and exploitation of all the natural resources within the country’s EEZ for Philippine nationals, corporations, and others authorized by the Philippine government. This inferred a more comprehensive and defiant strategy against Chinese maritime expansion grounded on the July 12, 2016, UNCLOS award to the Philippines.

CADC and the Philippines’ Alliance and Security Partnerships
CADC sees the need to foster the Philippines’ alliance and security partnerships with the U.S. and other American Indo-Pacific allies. For this reason, the Philippines engages in arms modernization and, more importantly, in alliance formation and coalition to constrain Chinese maritime expansion in the South China Sea and the waters of the first-island chain. CADC recognizes that the Philippines has a superpower ally and several security partners that can balance China's preponderant military power, which the AFP’s current modernization program cannot possibly counter or balance. The AFP’s force modernization program would be linked to its alliance and security partnerships. This necessitates the Philippine Navy (PN) and the Philippine Coast Guard (PCG) to hold periodic Multilateral Maritime Cooperative Activities (MMCA) with American, Japanese, and Australian naval forces. This is part of the Philippines’ ongoing defense posture shift to protect its maritime territories, particularly its EEZ.

CADC requires the Philippines to facilitate greater American strategic access to its territory.
This also entails the Philippines accepting and hosting a rotational deployment of the Littoral U.S. Marine Corps Regiment equipped with drones, Naval Strike Missiles, and the U.S. Army’s mid-range Typhon Missile system in Northern Luzon.
The two allies aim to develop their Anti-Access and Area Denial (A2/AD) posture to confine China’s growing power projection capabilities within the first-island chain.
Finally, CADC requires the Philippines to seriously engage the U.S., Japan, and Australia on how they can assist in integrating their battle networks and strengthening their air and sea capabilities with the AFP’s growing military capabilities. This would help offset the PLA’s efforts to destabilize the region’s military balance and impose China’s de facto control of the South China Sea and the waters of the first-island chain.

CADC and the Security of the First-Island-Chain
The Philippines' adoption and implementation of CADC addresses the strategic vacuum at the southern flank of the first-island chain. With the assistance of the U.S. and security partners, such as Japan and Australia, the AFP invests in its naval and air assets, urface-to-surface and air-to-surface missiles, and radars, communications,
and monitoring systems. This is aimed at developing the Philippines’ limited but evolving A2/AD defenses that will make it challenging for China to pursue its efforts at controlling the South China Sea through force. Strategically, the Philippines’ efforts at developing its military capabilities aim to complicate Chinese maritime expansion.
This will further convince Japan, Taiwan, and possibly South Korea to realize that it is in their national interest to prevent China from controlling any body of water and islands within the first-island-chain chain. In the event of China’s use of force, these states would likely coalesce and seek military assistance from their common ally, the U.S. This will, therefore, put in motion a strategy for the defense ofthe first-island-chain.