- Taiwan is roughly 100 miles from mainland China, but some Taiwanese islands are much closer.
- Amid rising tensions, those islands are increasingly vulnerable to attack from China's military.
- Taiwan's outlying islands would stand little chance against China, but they wouldn't be easy to take.
October marked the 73rd anniversary of the Battle of Guningtou, when Chinese Nationalist forces defeated an attempt by Chinese Communist forces to capture Kinmen, an offshore island that was seen as a stepping-stone toward Taiwan.
While celebrated, this year's anniversary was also a reminder of Taiwan's islands' growing vulnerability to Chinese attack.
In addition to the main island of Taiwan, Taipei controls five islands or island chains: Kinmen, the Mastu Islands, and the Penghu archipelago in the Taiwan Strait, and the Pratas Islands, also known as the Dongsha Islands, and Itu Aba, also known as Taiping Island, both in the South China Sea.
For the last 20 years, the islands in the strait have been seen as sites for interaction and bridge-building between Beijing and Taipei. But the vast majority of Taiwanese reject Beijing's diplomatic efforts to "reunify" the island and its territories with the mainland — a sentiment that has strengthened as Beijing's actions grow more aggressive.
With China refusing to rule out military force to take control of Taiwan and with the cross-strait military balance tilting toward Beijing, the islands are in an increasingly precarious position.
The islands
Taiwan's control over its outlying islands is the result of the People's Liberation Army's inability to seize them during the Chinese Civil War.
After Mao Zedong officially declared the People's Republic of China in Beijing on October 1, 1949, the only territory the Nationalists (KMT) controlled were the islands they had retreated to, the largest being Taiwan itself.
Mao's plans to invade Taiwan and other KMT-held islands were hampered by the PLA's lack of amphibious experience and the limitations of the still-nascent PLA navy and air force.
Beijing continued to threaten the islands after the Civil War, turning the strait into a tense area with clashes in the air, at sea, and on land during the first years of the Cold War. For decades, Chinese forces would regularly bombard Taiwanese-controlled islands in the strait.
While the US and Taiwan had a mutual defense treaty from 1955 to 1980, all but one of Taiwan's outlying islands were excluded, leaving the islanders uncertain about whether the US would come to their defense.
The risks
Taiwan's outlying islands are vulnerable mainly because their location. Taiwan itself is separated from China by the strait and its 100 miles of often rough waters. Taiwan's islands are much easier to reach.
Kinmen is the closest, a little more than a mile from China at the narrowest point, while the Matsu Islands are roughly 10 miles from mainland China. The Penghu archipelago is only about 30 miles west of Taiwan. The Pratas Islands and Itu Aba are located in the South China Sea farther south.
All are inhabited, though the Pratas Islands and Itu Aba only have small military garrisons.
China's military has grown rapidly in recent years. It is now much more capable than its pre-Cold War predecessor and much larger than its Taiwanese counterpart.
"We are looking at an actually more powerful PLA than anyone could have dreamed of back during the Cold War," Ian Easton, senior director at the Project 2049 Institute, told Insider. "The imbalance is remarkable now at the conventional level of warfare."
The PLA has as many as 416,000 soldiers in its Eastern and Southern theaters, which border the strait, according to the US Defense Department.
Taiwan only has about 5,000 troops stationed on its islands, down from roughly 100,000 during the Cold War. Taiwan's Navy and Air Force have also gotten smaller and are more vulnerable to nearby Chinese forces, limiting their ability to reinforce the islands.
"Taiwan has very little ability to move defensive assets to Kinmen and Matsu given the variety and number of anti-ship and anti-air missiles China has available on the coasts," said Timothy Heath, a senior international defense researcher at the Rand Corporation think tank.
Their proximity to the mainland also makes US intervention on their behalf a risky proposition, as US warships and planes would also be vulnerable to Chinese coastal air and naval defenses.
Despite being farther away, the Pratas Islands and Itu Aba are also vulnerable. Their small garrisons would stand virtually no chance against the Chinese military's full might, and, in the event of a full-scale Chinese attack, they would receive little help from Taiwan.
Worst-case scenarios
Taiwan's islands face a number of worrying scenarios, from blockades to helicopter assaults and all-out amphibious invasions, but Taiwan has taken steps to ensure that even with smaller garrisons, the islands be more than just afterthoughts for the PLA.
Taipei has deployed a substantial number of missiles to Kinmen, the Penghus, and the Matsu islands. Given their location, they could directly threaten PLA staging areas and critical infrastructure in southeast China, particularly in the cities of Xiamen and Fuzhou. The islands could also be used to launch Taiwanese loitering munitions.
"It would be very difficult and dangerous for the PLA to try to move on Taiwan proper without first suppressing those islands," said Easton, who has written extensively about the defense of Taiwan.
Many of the islands are honeycombed with bunkers and tunnels and are protected by some of Taiwan's best marines and special-forces units, who are trained specifically to fight with little support.
"Those islands are going to be very hard to take," Easton told Insider, adding that the PLA may need as much as a 10-to-1 advantage to capture the more fortified islands, such as Dongyin in the Matsu Islands.
"They would be very bloody battles, and the Taiwanese could do a lot of damage to critical infrastructure in the southeast of China, especially around Xiamen and Fuzhou, which are absolutely critical strategic areas," Easton said.
"They are not defendable over the long run, but it would force the PLA to pay a terrible price to take them," Easton added. "The idea is that this would give the Taiwanese more time back on the home island to prepare."
Even with the islands under Chinese control, the PLA would then have to ensure their control can be maintained. This would be difficult in the Penghus, which are much closer to Taiwan.
"The challenge for the Chinese is that resupplying and sustaining troops on islands so close to Taiwan would probably be difficult so long as Taiwan could maintain artillery and other fires to endanger any resupply and aircraft," Heath told Insider.
It is unlikely that China could blockade the islands into submission or take them without invading Taiwan itself.
Though the US and Taiwan no longer have a mutual defense treaty, President Joe Biden has said several times that the US would intervene if China used force against Taiwan. (The US has not made a formal commitment to defend Taiwan against a Chinese attack, and White House officials say Biden's comments are not a policy change.)
Even if the US does not intervene in the event China seizes or blockades Taiwan's islands, such actions by Beijing are likely to increase US public support for Taiwan and could prompt the US to provide extensive military and diplomatic support, like that given to Ukraine following Russia's attack.
"The real problem for China is the escalation potential of starting a conflict over those islands," Heath said. "China will have started a war with Taiwan and potentially with the United States. And once a war begins, as Putin has learned in Russia, it can be quite difficult to find a way out."