By: Jens KastnerPhoto from the Philippine StarIn late February, the Philippine, US and Japanese militaries for the first time moved their joint “Multilateral Maritime Cooperative Activities (MMCA)” military exercises from the South China Sea to the Bashi Channel that separates the Philippines from Taiwan, a shift that serves as a key focal point of strategy for the US and its allies to restrain China’s maritime expansion and deter a potential Taiwan invasion.The drills’ geographical focus is Mavulis Island, a 2.2 sq. km uninhabited outcrop 142 km from Taiwan and 200 km from the northernmost tip of Luzon. The island is garrisoned by Philippine troops who have constructed a shelter for local fishermen, a water desalination plant, a helipad, lighthouse, and a hilltop flagpole.Mavulis shares conspicuous characteristics with Japan’s westernmost Yonaguni Island, which is readying for a dramatic militarization effort owing to its geographical closeness to Taiwan, with Japan’s Defense Minister Shinjiro Koizumi in late February unveiling the government’s plans to deploy surface-to-air missiles at Yonaguni. That follows a suggestion by Japanese Prime Minister Sanae Takaichi in late 2025 that Japan would militarily intervene if China used armed force or a naval blockade against Taiwan.Whereas the Japanese military has had a base with electronic warfare units on Yonaguni since 2016, the Philippine Navy and Marines began using Mavulis with small detachments in 2023.“Conducting military exercises in the waters surrounding Mavulis Island carries significant strategic importance, as the area lies near the northern entrance of the Bashi Channel, which, together with the Balintang Channel, forms the main maritime routes of the Luzon Strait,” said Hung Tzu-Chieh, an associate research fellow at the Institute for National Defense and Security Research, a public think tank in Taipei. “This strait is a key route for the Chinese Navy, particularly its submarine forces, to move from the South China Sea into the Western Pacific. If the island were further militarized, it could potentially serve as a strategic monitoring node for activities in the strait.”Hung went on to explain that Mavulis Island covers only about 2.2 square kilometers and is characterized largely by steep rocky coastlines, lacking a harbor and basic infrastructure. Whereas Hung sees these geographical constraints as imposing significant limitations on the long-term deployment and sustainment of military facilities, another observer thinks they are an actual advantage.“These northern islands are almost empty of locals and a Chinese attack on US forces on these rocks helps exclude the main island [Luzon] from direct attack by Chinese missiles/fighter jets,” said Wendell Minnick, a veteran Taipei-based military analyst and the editor of the China in Arms Substack blog.Similarly, James Holmes, a professor at the US Naval War College, said any outpost in or adjoining the Luzon Strait and Bashi Channel is going to have value, given that it is China’s best maritime gateway to the Western Pacific. According to Holmes, waters are deep enough and have rough-enough environmental conditions that submarines could slip past US or allied antisubmarine defenses.“A standing allied presence would reduce its value to China, helping the allies seal off the First Island Chain to China’s navy in keeping with longstanding practice, which was codified most recently in the 2026 National Defense Strategy,” Holmes said, referring to a strategy released by the Trump administration in January that, among other things, focuses on the First Island Chain between Japan, Taiwan and the Philippines for deterrence by denial.While no formal defense ties exist between the Philippines and Taiwan, the Philippines is obviously warming to the idea of a Taiwan contingency, as indicated by the government under Ferdinand Marcos Jr in 2023 allowing the US military to use a naval base in Cagayan facing Taiwan under the Enhanced Defense Cooperation Agreement (EDCA) and deploy a Typhon missile system in Ilocos Norte, also facing Taiwan. In November, a US congressional body, the US-China Economic and Security Review Commission (USCC), raised eyebrows by recommending that Taiwan bankroll improvements to EDCA sites in the Philippines, a proposal it believes will boost the US’s ability to defend Taiwan from a potential invasion from China.“If Taiwan funded Philippine military facilities, the US would likely shepherd the deal, conducted secretly to avoid domestic backlash in Taiwan and severe diplomatic repercussions from Beijing for Manila,” said Lucio Blanco Pitlo III, president of the Philippine Association for Chinese Studies. “The Philippine military would likely welcome support given persistent budget constraints and domestic issues like corruption.”However, Pitlo went on to caution that these steps irritate Beijing and may complicate its planning but are unlikely to change China’s fundamental objective on Taiwan. “If reunification is central to CPC legitimacy, such efforts may only delay timelines rather than prevent action, as allied deployments are modest compared to the PRC buildup along the Fujian coast,” Pitlo said, referring to mainland China’s closest to province to Taiwan.Pitlo believes that the recent joint MMCA exercises around Mavulis were oriented towards a meeting between US President Donald Trump and Chinese President Xi Jinping that had initially been scheduled but has been delayed by the Iran situation, with Trump signaling his intention to postpone it.“Amid the escalating conflict in the Middle East, Washington may be sending a message that it can fight on multiple fronts, that redeployment of troops and arms from one theater to another does not adversely affect its posture in the Indo-Pacific, and that its regional allies are stepping up in terms of security burden sharing,” Pitlo said.