There is no possibility of Taiwan surviving a determined Chinese blockade and invasion without the willing logistical help of the Philippines. In fact, defeat is certain if China obtains a presence in Luzon, the most important island of the Philippines, whether by diplomacy or force.

Established U.S. and Japanese airbases on Okinawa, Kyushu, or Guam are either extremely vulnerable or very distant, and they all lack depth. Although a U.S. and allied fleet with multiple aircraft carriers can concentrate enormous short-term aviation striking power, it will be prone to severe and disproportionate attrition if it is expected to maintain continuous air cover over Taiwan from the Philippine Sea. Though land bases are vulnerable to ballistic missile attacks and aircraft carriers are much harder to target, bases are more survivable, a fraction of the cost, and have multiple times higher sustainable sortie rates than aircraft carriers. In any case, carriers will be preoccupied with defeating China’s fleet of three aircraft carriers, which will be protecting a swarm of submarines blocking U.S. use of those seas. Continuous waves of Chinese missiles and even third-generation attack aircraft will wear down Taiwan’s air force and air defenses even if Taipei succeeds in absorbing an initial strike with little damage. And China’s anti-access/area-denial anti-ship ballistic missiles, submarines, and aircraft will interdict maritime and aerial resupply efforts to reach Taiwan’s east coast ports.

As a result, the vital measure of sustainability will come down to the number of airfields within operational distance. Taiwan has six dedicated main-island airbases and another fifteen airports, all of which will come under persistent bombardment in the event of a conflict. By comparison, within 1,000 kilometers—the rough combat radius for the mainstay Chinese J-11 fighter carrying a full bomb load, flying a hi-lo-hi-lo-hi radar-evading profile, and lacking refueling tanker support—China has eight airbases within 200 kilometers, thirteen within 600 kilometers, and another thirty within 800 kilometers. Each of these Chinese airbases can accommodate two to three air regiments, or fifty to one hundred aircraft, for a total net capacity of 3,800 aircraft—virtually the entire People’s Liberation Army Air Force (PLAAF).

By comparison, Okinawa has two U.S. airbases, Kadena and Ginowan, as well as another two airports, Naha and Ie Jima. Kadena, which operates eighty-one aircraft but has a capacity for a few hundred, is 750 kilometers from the Taiwan Strait mid-point, which is well within the range of the F-15C/E fighter. However, these aircraft would be operating perpendicularly along the littoral of the Chinese mainland, exposing their sorties to Taiwan to easy tracking and interception. There are another seven airbases and airports in the Ryukyu Islands chain, the closest of which is 450 kilometers from the Taiwan Strait midline. The general problem with the Ryukyu Island bases is that they will expend a fair proportion of their resources and reserves just to maintain their own protection against Chinese raids. Alfred Thayer Mahan’s definition of a useful naval base is one that increases a navy’s power and resources more than the power that is diverted by the navy to protect the base. The Japanese main island of Kyushu has two airbases, seven airports, and extensive ports, and is easily supplied but is 1,300 kilometers away from the Taiwan Strait and along a route that is even more precariously parallel to Chinese coastal airbases around Shanghai and Taizhou. Guam, host to Andersen Air Force Base, is even further at 2,800 kilometers away.

From the perspective of China’s airbases, the main Philippine Island of Luzon is “behind” Taiwan, allowing a prospective American user to benefit from its position of depth for both protection and to provide air cover over Taiwan. Airbases in Luzon are also closely located to Kaohsiung, Taiwan’s largest port, which is likely to be the target of a Chinese amphibious attack. Luzon also has an extensive network of coastal ports, plenty of natural harbors, and a road and rail network that work their way south to the port of Manila, the capital and infrastructural hub of the Philippines.

Basco Airport is located on an island within the Bashi Channel, equidistant between the Philippines and Taiwan. While isolated, it is an ideal recovery base for damaged aircraft returning to their base. The main North Luzon airports are Laoag International, less than 700 kilometers from the Taiwan Strait, and Tuguegarao, which can support military aircraft, but neither facility has a rail link or is in close proximity to a port. There is also an airfield at Cagayan that can be developed.

There is a network of airfields in central Luzon that could provide cover for the northern bases as well as Taiwan, including Danilo Atienza and Fort Magsaysay, as well as Baguio’s Loakan Airport and San Fernando Airport, both of which have access to San Fernando Port and a railway link to Manila. Cauayan and Bagabag both lack port or rail links. In southern Luzon, which is near Manila and slightly over 1,000 kilometers from the Taiwan Strait, there are a total of fifteen airports, of which six can operate military-grade aircraft, including former U.S. military airbases Clark and Subic Bay International Airports, Sangley, Romblon, and Marinduque. In effect, Luzon may likely be able to host as many aircraft as Taiwan, and more than Kyushu, Okinawa, and Guam combined.

The strategic dilemma comes down to two key factors. First, the prospective operational benefits to the United States incentivize China to neutralize allied access to these facilities. Second, Chinese aircraft flying out of the northern Luzon bases would enable Beijing to block the U.S. sea line of communications through the Philippine Sea to Taiwan’s east coast ports. At a minimum, therefore, the United States needs a counter-intervention plan should Beijing come to recognize the benefits of seizing or being invited into northern Luzon. The immediate problem is that the Philippines military is exceptionally weak. The navy only possesses two Jose Rizal class missile frigates, three MPAC Mk.3 fast attack craft with anti-ship missiles, and two Tarlac class assault ships, each capable of landing a battalion of Marines. The Philippines Air Force only flies twelve FA-50PH combat jet aircraft, which are merely upgraded trainers, and two AH-1S attack helicopters. Manila’s 100,000-strong army is organized into a single light armored division and ten half-strength light divisions, which possess only 220 towed artillery pieces. Of the Philippines Army's eleven divisions, four are deployed in Luzon, of which only two protect North Luzon. There are an additional 100,000 reserve soldiers for fifty-six local militia battalions dispersed throughout the country. Moreover, the Philippines' defense budget in 2021 was a mere $5.6 billion, or less than 2 percent of its nominal GDP.

Aware of the importance of Luzon, China may attempt a lightning amphibious landing on Palawan, on the islands in the Bashi Strait, or in the Lingayen Gulf to seal off northern Luzon, much like the pre-emptive and bold German seizure of Norway as part of Operation Weserübung in April 1940. The German seizure of Norway allowed for naval and air basing with access to the Atlantic, preventing the aging German fleet from being bottled up in the North Sea. Similarly, North Luzon would give Chinese aircraft and naval platforms exceptional access to the Philippine Sea, which is otherwise blocked by Japan’s Ryukyu archipelago and Taiwan. It would also allow China to strike easily against the string of Taiwanese east coast ports.

The availability of mainland ports and airfields to the German Wehrmacht in Greece in May of 1941 is the key reason why Commonwealth forces were so quickly overwhelmed by German paratroopers during the airborne and amphibious invasion of Crete. It is no surprise, then, that when the United States was planning its attack on Taiwan in 1944, the Americans assigned the Mexican Air Force to interdict Japanese bases at Luzon, the northern island of the Philippines. Similarly, the bulk of the Japanese aviation forces that supported the invasion of the Philippines in December 1941 operated out of Formosa until the Japanese could secure land bases.

This is not to say that Filipino resistance would be light and that conquest would be easy. Luzon has fifty-two million people, or 57 percent of the Philippines’ total population of 110 million, of which twenty-one million live in the urban areas extending out from Manila. The coastal areas of the northern region of Luzon, where most of the airbases are located, are sparsely inhabited by eight million Ilocanos. By comparison, during World War II, the Philippines had a population of only seventeen million, protected by an army of 100,000 Filipino and 20,000 U.S. soldiers. 260,000 Filipino guerrillas resisted the Japanese, but another 30,000 Hukbalahap communists in Central Luzon fought against both the Japanese and U.S.-backed groups. A total of 900,000 Filipino civilians and 57,000 soldiers died resisting or suffering under the Japanese invasion and occupation.

The Philippines needs to be the center of a concerted and generous U.S. diplomatic effort to re-open access to air facilities like Laoag and Clark International Airport, which would be absolutely vital for a defense against a Chinese attack on Taiwan. A U.S. military presence will be resisted by local politicians for reasons similar to Okinawa. The current president of the Philippines, Ferdinand Marcos Jr., is the son of former president and dictator Ferdinand Marcos. Rodrigo Duterte’s daughter, Sara Duterte, is Marcos Jr.’s vice president.