How Japan Can Help Save Taiwan: Securing the First Island Chain

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Russia’s invasion of Ukraine has taught Taiwan many lessons about preparing for a possible Chinese invasion. Japan should also take this opportunity to learn. What more can Japan’s Self-Defense Forces do to prepare given their inevitable participation in any potential conflict over Taiwan?

Based on the Chinese Communist Party’s unwavering resolve to annex Taiwan, the People’s Liberation Army (PLA) has been developing air and naval forces as the major element of anti-access/area denial capability. Now, PLA air and naval assets can reach beyond the first island chain into the Western Pacific. However, Beijing does not control any land in the first island chain. Therefore, the PLA needs to secure, by force, passages for their air and naval assets to gain access deeper into the Pacific Ocean. The PLA’s shortest passages from China’s mainland to the Pacific Ocean are on the north and south sides of Taiwan. The former is through Japan’s Southwest Islands between Japan’s mainland and Taiwan, and the latter is through the Luzon Strait between Taiwan and the Philippines. The former consists of about 200 islands and is about 650 nautical miles (1,200 kilometers) long. The latter consists of about 35 islands and is about 135 nautical miles (250 kilometers) long. Both areas are only 270 to 430 nautical miles (500 to 800 kilometers) away from China’s mainland and, in the event of a conflict, would likely be exposed to fierce PLA attack to secure air and naval passages.



No one knows when China intends to invade Taiwan, but given China’s rapidly growing military capabilities and increasingly aggressive actions, preparing for this scenario is an urgent issue for Japan, the United States, and other like-minded countries. In an invasion, Beijing will rely on the PLA’s anti-access/area denial capability to disturb any military intervention by the United States and other countries. Therefore, countermeasures against these will be essential to deter and, if necessary, respond to any Chinese invasion attempt. However, it would be difficult, if not impossible, for the United States to conduct effective countermeasures alone. Close cooperation between the United States and allies in this region, including the sharing of roles in countermeasures, is critically important.

What follows in this article is first a brief discussion of current United States and Japanese thinking and actions on the subject. Then, the article transitions to providing recommendations for what the Japan Self-Defense Forces should do next to maximize their ability to help deter such a Chinese invasion in the first place, and — should Beijing choose to attack regardless — to help ensure the attack fails.

Japan Needs Expeditionary Advanced Base Operations, Too

The U.S. Marine Corps is now developing the concept of expeditionary advanced base operations. This is a form of expeditionary warfare that involves the employment of mobile, low-signature, persistent, and relatively easy to maintain and sustain naval expeditionary forces. The most prioritized mission of expeditionary advanced base operations is to support sea control by the U.S. Navy. Expeditionary advanced bases are established as temporary bases ashore or inshore within a contested or potentially contested maritime area to conduct sea denial, support sea control, or to enable fleet sustainment.

An expeditionary advanced base consists of assets for information, surveillance, reconnaissance, anti-ship warfare, air and missile defense, antisubmarine warfare, and logistics. Expeditionary advanced base operations are expected to be a countermeasure against the PLA’s anti-access/area denial threat in the first island chain, among other contested littoral regions. Japan’s Southwest Islands and the Luzon Strait, critical maritime terrain facing China and next to Taiwan, would be suitable for expeditionary advanced base operations.

The U.S. Marine Corps has a plan to establish three littoral regiments in the Indo-Pacific theater. These regiments will be the core unit of expeditionary advanced base operations and will include a headquarters, a littoral combat team, a littoral logistics battalion, a littoral anti-air battalion, and other units. A littoral combat team will have three infantry companies and an anti-ship missile battery. However, considering the length of the first island chain, three such regiments will not be sufficient to ensure robust sea denial in all areas. To prevent a sea-denial gap in the first island chain, it is essential that the United States’ allies, such as Japan, rapidly develop similar capabilities.

Japanese and Philippine Defense Posture in the First Island Chain

There is a big difference in the defense posture between the Southwest Islands and the Luzon Strait. Regarding the Southwest Islands, Chinese operational behavior in the waters around the Senkaku Islands in the western part of this island chain has been challenging Japanese territorial sovereignty. For example, the Japan Coast Guard reported the number of Chinese government vessels intruding into Japanese territorial waters around the Senkaku Islands was 108 in 2021. Against the backdrop of this tension in the Southwest Islands, the military has been enhancing Japan’s defense posture. The Ground Self-Defense Force is now deploying anti-ship missile batteries, air defense batteries, infantry units, support units, and intelligence units on some islands. New electromagnetic units will be deployed in the near future. The Air Self-Defense Force has doubled the number of fighter aircraft on the airbase on Okinawa Island. And the Maritime Self-Defense Forces around the Southwest Islands seem to be activated recently. On the other hand, too little is being done to enhance the defense posture of the Luzon Strait.

Meanwhile, it was recently reported that India has decided to supply the Philippines with the BrahMos supersonic anti-ship missile system. This missile system has an estimated 160 nautical mile range (290 kilometers). If the Armed Forces of the Philippines install these missile systems — and also develop the required sensor and communication architecture to effectively employ them — in the northern part of the Philippines, they can cover all waters of the Luzon Strait. However, the Philippines’ capabilities for air defense, anti-submarine warfare, and electromagnetic warfare are known to be extremely limited. Therefore, the PLA would likely still have a relatively easy passage into the Pacific Ocean going through the Luzon Strait when compared to the Southwest Islands option. The PLA’s recent provocative flight through the southern part of Taiwan’s air defense identification zone might be an indication that Beijing currently believes the Luzon Strait entrance into the Pacific Ocean is vulnerable.

Given the gap in defense posture between the Southwest Islands and the Luzon Strait, the latter is a weakness. Therefore, the U.S. Marine Corps would do better to allocate its limited resources for expeditionary advanced base operations to the Luzon Strait. If the U.S. Marine Corps were to deploy its littoral regiments in this area, along with the service’s F-35B and forthcoming MQ-9 maritime surveillance squadrons, it would enhance the sea-denial posture on the south side of Taiwan. Fortunately, the Philippines’ Batanes Islands and the Babuyan Islands are located in the Luzon Strait. Those islands and the northern part of Luzon Island are suitable to enable the establishment of partnered expeditionary advanced bases alongside the Philippines armed forces.

Challenge for the Japan Self-Defense Forces

If the U.S. Marine Corps focuses primarily on the Luzon Strait, Japan’s forces will likely have to conduct sea-denial operations against the PLA mostly if not exclusively on their own. What changes should they make to ensure they are properly prepared for such a situation?

In the initial phase of a potential Chinese invasion of Taiwan, the PLA will likely attack military assets and facilities in and around Japan to prevent the Japan Self-Defense Forces from cooperating with U.S. forces. This attack would likely be sudden, massive, and conducted in a sophisticated manner by air, naval, missile, drone, electromagnetic, cyber, and special operations. Unfortunately, it would be difficult for Japan to prevent this attack and keep air and maritime superiority around the Southwest Islands. Therefore, its forces need to find ways to conduct sea denial in this situation.

The current Japanese strategy to defend the Southwest Islands consists of three phases. The first phase is deterrence by units located in the Southwest Islands in peacetime, the second phase is reinforcement by units from Japan’s mainland to enhance the defense posture, and the last phase is retaking the islands, should the PLA successfully invade them. In the last phase, the Amphibious Rapid Deployment Brigade located on the mainland would attempt to conduct an amphibious assault with support by the air and maritime forces. However, considering the PLA’s likely air and maritime superiority around the Southwest Islands in time of war, such an assault, including a long voyage and flight from Japan’s mainland, would be very dangerous and likely lead to thousands of casualties. This is a serious challenge for the Japan Self-Defense Forces. 

How the Japan Self-Defense Forces Should Deal with This Challenge

To deal with this serious challenge, the Japanese forces should revise their current strategy to a more feasible one with a much higher probability for success. In this revised strategy, most missions for deterrence, reinforcement, retaking islands, and sea denial would be carried out by units located in the Southwest Islands. This will require significantly enhancing the limited capabilities of the forces forward-deployed on the islands.

The Air Self-Defense Force’s runways in the Southwest Islands will likely be destroyed by the PLA in an attack. Therefore, it will need to consider deploying Japan’s F-35Bs in this area for air defense and sea denial, as these aircraft are specifically designed to operate from shorter-range expeditionary airfields. The air force has a plan to purchase 42 F-35Bs. However, these aircraft are currently planned for operation from Izumo-class helicopter carriers of the maritime branch, not from forward positions within the islands. Considering that large vessels such as these carriers are increasingly vulnerable to PLA air and maritime capabilities, it is time to re-envision how Japan will employ its F-35Bs. With this new approach, it will also be necessary to build many dispersed bunkers for F-35Bs in the Southwest Islands, capable of rearming, refueling, and providing maintenance while avoiding attacks by the PLA. At the same time, fixed-radar sites in the Southwest Islands will likely be destroyed by the PLA in the initial phase of the conflict. The air branch therefore needs to deploy more survivable and sustainable measures for air awareness including unmanned aerial vehicles and mobile radar systems.

The Maritime Self-Defense Force now deploys more than 10 fixed-wing anti-submarine patrol aircraft and two mine sweepers in the Southwest Islands, but the former will be difficult to operate in the event of a conflict, because their runways will almost certainly be destroyed. Therefore, the maritime branch needs to deploy many unmanned surface/underwater vehicles that can survive PLA attack. These unmanned vehicles will be useful for maritime awareness, anti-ship warfare, anti-submarine warfare, and mine warfare. Fortunately, the Maritime Self-Defense Force has already begun developing unmanned underwater vehicles.

The Ground Self-Defense Force is scheduled to deploy three anti-ship missile batteries in the Southwest Islands by 2023, but this is too few considering the damage expected from the opening salvos of PLA attack. Therefore, it needs to deploy more intelligence units to the Southwest Islands, as well as anti-ship missile batteries, air/missile defense batteries, infantry units, electromagnetic units, support units, and a stockpile of ammunitions and supplies for sustainable and robust activities. On the other hand, given the limited number and size of training areas for the ground force in the Southwest Islands, rotating well-trained units from Japan’s mainland would be an effective way to keep high operational readiness.

At the same time, the Ground Self-Defense Force needs to pre-position some detachments of the Amphibious Rapid Deployment Brigade in the Southwest Islands in order to avoid serious danger during the long voyage and flight from Japan’s mainland. These detachments can conduct more agile amphibious operations to other islands nearby. The mission of these detachments will not only involve retaking islands but also establishing temporary bases in other islands for sea denial with anti-ship missile batteries and other units. This will confuse the PLA’s intelligence activities and targeting and provide opportunities of robust sea denial. This is a new type of operation for the brigade, akin to the U.S. Marines’ expeditionary advanced base operations concept.

Moreover, either the ground or maritime force needs to invest in island-hopping transportation capability for reinforcement, retaking islands, and sea denial. Considering the fierce contested situation, fast and low signature landing crafts and fast patrol/escort boats should be deployed in the Southwest Islands. Currently, neither the ground nor maritime branches have these types of platforms. Procuring the readily available BMT Caimen-90 tri-bow fast landing craft, which is the design base of the Maneuver Support Vessel (Light) of the U.S. Army, along with the U.S. Navy’s Mark VI patrol boat, would go a long way toward addressing current littoral mobility deficiencies. Regarding landing crafts, some 30 Caimen-90s should be deployed in the Southwest Islands. They can carry a package of units to establish a temporary base for sea denial in other islands. Those units would comprise an infantry company of the amphibious brigade, an anti-ship missile battery, an air defense battery, and support units. Additionally, the ground force should deploy more than 10 CH-47 heavy cargo helicopters in the Southwest Islands for swift island-hopping transportation.

Combined with the above recommended changes, all three branches should change their current posture and primary large-signature operating constructs, as these are increasingly vulnerable to surprise attacks and lacking in sufficient force protection. In place of these operating constructs, the Japan Self-Defense Forces should prioritize distributing forces, deception, camouflage, concealment, decoys, and anti-drone measures.

Moreover, the Japanese military should establish a joint command and control function for the forces operating around the Southwest Islands to enable maximum collective situational understanding and the coordination of actions. If units of the different branches continue to be commanded separately by their higher commands located in Tokyo, flexible operations tailored to local situations would be difficult. At the same time, the robust defense posture covering both the Southwest Islands and the Luzon Strait will need a combined approach by Japanese and U.S. forces. Establishing a platform for the coordination and cooperation — a Standing Combined Maritime Joint Task Force, for example — should be considered.

Furthermore, one important mission for the Japanese forces is to protect civilians. About 1.5 million Japanese citizens live in the Southwest Islands. Fierce World War II battles in this region led to more than 90,000 civilian casualties. In addition to protecting Japanese civilians, the military needs to be prepared to protect tens of thousands of civilians who will presumably evacuate from Taiwan into the Southwest Islands to avoid the primary PLA assault location. If the Japanese forces want to focus their efforts on combat missions, thorough preparation for the protection of civilians in cooperation with local governments and other responsible organizations will be needed.

Change Is Both Possible and Urgently Needed Now

If the Japan Self-Defense Forces and the U.S. Marine Corps establish sea-denial zones on the north and south sides of Taiwan, the U.S. Navy would then be able to focus on conducting operations for broader sea control in the East China Sea and the northern part of the South China Sea. At the same time, U.S. Air Force aircraft can fly there, and the U.S. Army’s Multi-Domain Task Forces with medium- and long-range missiles can deploy there. This posture will have strong impacts on China’s intention and capability to invade Taiwan.

By the end of 2022, Tokyo will revise Japan’s central guiding documents for national security and defense. These documents, the National Security Strategy and National Defense Program Guidelines, were last updated in 2013 and 2018, respectively. Much has changed in the intervening years. Given these changes, especially in PLA capabilities and increasingly assertive and coercive behavior, major revisions to both documents are essential. Ukraine’s lessons for Japan should be also considered. How to carry out robust sea denial around the Southwest Islands needs to be one of the main focuses.



Nozomu Yoshitomi is a retired major general of the Japan Ground Self-Defense Force. After retirement, he has been a professor at the College of Risk Management, Nihon University, in Tokyo. He is also an associate of BMT Group Ltd.

Image: U.S. Navy (Photo by Mass Communication Spc. 2nd Class Aaron T. Smith)