Amid the strategic competition and simmering tensions in the Indo-Pacific region between the United States and China, Japan has worked to boost its military capability on Yonaguni Island, the westernmost island of Okinawa. This is a sensible move given the island’s strategic importance and proximity to both Taiwan and China. The Japan Self-Defense Forces established a military base and radar station in 2016 with approximately 160 troops to monitor airspace and waterways. Plans are also in place to deploy a missile unit to the island.
To the south, a little less than 250 miles away, lies Mavulis Island. Slightly smaller than Yonaguni Island, it shares many of the same characteristics. Just as Yonaguni Island is the westernmost piece of Japanese territory, Mavulis Island is the Philippines’ northernmost point. Similarly close to Taiwan, it likewise has a strategic importance disproportionate to its size. Mavulis Island may appear to be a seemingly insignificant speck on the vast blue map of the region, but it may be the linchpin of the defense of Taiwan. What is more, the Bashi Channel that lies between Mavulis Island and Taiwan’s Orchid Island will likely be utilized as a primary route for the People’s Liberation Army Navy (PLAN) to blockade the island and isolate it from US and allied forces. In short, Mavulis Island could be a key terrain in any Taiwan conflict scenario.
And yet, compared to Japanese action on Yonaguni Island, the Philippines has not given Mavulis Island similar treatment. This is a missed opportunity to strengthen deterrence against China in the region and, in the event of a conflict, counter any Chinese aggression against Taiwan. It is in the United States’ interests to encourage Manila to take advantage of the island’s strategic importance.
While narrow, the Bashi Channel serves as a critical conduit between the Pacific Ocean and the South China Sea. As a chokepoint, its strategic position influences the operational capabilities of major naval forces of the United States and its allies. Pundits postulate that chokepoints such as the Bashi Channel could dictate the outcome of a potential Chinese invasion of Taiwan because of its ability to control access into the Pacific Ocean. The Bashi Channel’s importance is further magnified by its relevance to submarine warfare as the deep waters of the channel provide an ideal environment for the PLAN’s operations. China would likely utilize these waters for concealment and to strategically position the PLAN to achieve Beijing’s overall military objectives. The Bashi Channel, therefore, should influence broader maritime strategy against a potential Taiwan invasion.
Mavulis Island could serve as be a key focal point of the United States’ and its allies’ strategies to restrain China’s maritime expansion and deter a potential Taiwan invasion. Stepping up efforts on the island to match Japan’s actions on Yonaguni Island would help to limit the PLAN’s movement within the Indo-Pacific region. A central goal of both sides in the US-China strategic competition in the region is establishing and maintaining key locations. The PLAN’s increased activities around the Philippines highlight its strategic objective of securing unrestricted access through the Bashi Channel. Thus, it is in the United States’ and its allies’ interests to control the strategic waterway.
The Bashi Channel is indispensable for Taiwan’s defense and for regional stability. One can posit that China’s military strategy for the channel treats it as a potential route for the People’s Liberation Army to encircle Taiwan, posing a direct threat to peace and security. Any attempt by Beijing to invade the island will almost certainly utilize the Bashi Channel for military operations. These will have immediate and profound implications for Taiwan’s defense posture. The PLAN’s continuous operations in and around the Bashi Channel reflect Beijing’s ambitions to extend its power beyond the first island chain and into the Pacific Ocean. Thus, controlling key waterways in the chain of islands—like the Bashi Channel—is crucial for any prospective US intervention in support of Taiwan. Moreover, ensuring open and secure access through the Bashi Channel would enable rapid deployment and sustainment of US forces and allies in the event of a crisis.
As another major ally in the region, the Philippines can also deploy advanced surveillance systems in Mavulis Island to strengthen its maritime domain awareness (MDA) while monitoring China. The United States can utilize the annual Balikatan exercise to enhance real-time monitoring of vessel movements into a broader network of sensors to contribute to a comprehensive MDA framework. Since the MDA network can track both surface and subsurface PLAN maritime activities, it would be crucial in giving the United States and its allies information superiority in this area.
The establishment of a Philippine Navy detachment on Mavulis Island in October 2023 marked a significant step in reinforcing Manila’s northern defenses. The presence of military assets on the island sends a clear message of commitment to regional security by the Philippines’ government. But more can be done. The United States and the Philippines can conduct, in partnership, maritime key terrain security operations around Mavulis Island to demonstrate the strategic value of forward-deployed forces in deterring China’s actions. The strategic positioning of military assets on Mavulis Island contributes to a credible deterrent. Yet, Mavulis Island could also serve as a forward operating base to strengthen and reinforce this deterrent. Establishing such a forward operating base on the island would cement its role in enhancing the Philippines’ defense posture.
The Bashi Channel’s strategic importance becomes immediately apparent just by looking at a map, given its position within the first island chain, a series of archipelagos stretching from Japan through Taiwan and the Philippines. This chain represents a key perimeter for the United States and its allies aiming to counter China’s maritime expansion. Having control over the Bashi Channel, therefore, enables monitoring of—and if necessary, influence over—the PLAN’s movements between the Pacific Ocean and the South China Sea, making it a focal point in the broader US strategy to isolate and deter China’s aggressive posture.
China has increasingly employed gray zone tactics in the region, utilizing maritime militia and coast guard vessels to assert its claims without crossing the threshold into open conflict; these actions aim to achieve strategic objectives while avoiding direct military engagement. Such maneuvers exemplify China’s strategy of using nonmilitary means to apply pressure and alter the status quo in contested maritime regions. Multilateral security cooperation is necessary to address these issues. To balance China’s gray zone activities and maintain stability and cooperation between external powers, forums like the Quadrilateral Security Dialogue (QUAD) are key. The QUAD seeks to maintain a free and open Indo-Pacific and improve collective security through coordinated diplomatic efforts, intelligence sharing, and cooperative military exercises to prevent coercive activities and preserve the strategic balance in vital waterways—like the Bashi Channel.
Understanding and recognizing the importance of chokepoints like the Bashi Channel is crucial for formulating effective policies to navigate the complex security landscape of the Indo-Pacific. The security dynamics and geographic realities of the Bashi Channel necessitate strong regional partnerships to deter and respond to threats. The United States, Japan, and the Philippines have intensified combined military exercises, enhancing their interoperability and their collective deterrence capabilities. Meanwhile, Australia is expanding its role in the region with intelligence-sharing initiatives and coordinated maritime patrols. These relationships are critical for countering China’s gray zone tactics and ensuring a free and open Indo-Pacific.
But also critical is controlling key terrain. The Bashi Channel is not just a maritime passage—it is a strategic flash point where geopolitical rivalries converge. Mavulis Island is therefore a piece of key terrain, influential in shaping security dynamics in the region and a means of contributing to stability and the defense of US allies and partners. Just like Yonaguni Island to its north, it should be treated as such.
