ANALYSIS/Assessing indigenous subs in Taiwan's defense strategy: Insights from U.S. experts

By Sean Lin, CNA staff reporter

The question of whether Taiwan needs submarines has always been divisive. With the unveiling of the Narwhal, the country's first indigenous defense submarine, on Sept. 28 renewing the age-old debate, military experts deep-dived into the pros and cons of Taiwan's submarines and how they could potentially be deployed in a cross-strait conflict.

Eric Heginbotham, principal research scientist at MIT Center for International Studies, told CNA that submarines are "highly effective at sea" in that they are "hard to find" and thus have a higher survivability than surface ships, which are "extremely vulnerable."

Comparing submarines with Taiwan's Lafayette-class frigates, Heginbotham said while these two weapons are both expensive, a submarine "should get a chance to shoot before it dies," while a Lafayette is just "flaming, sinking hulks from minute one in a war" and "won't even get a chance to fire one missile."

Fear factor

Due to submarines' stealthiness, the "fear factor" of trying to operate against them is greater than other anti-ship platforms, such as missiles, which is a "big plus," Heginbotham said.

Citing the Falklands War in 1982, Heginbotham said the British Navy had already had some ships sunk by Argentina using missiles and bombs. To prevent more loss of ships, the British fired hundreds of torpedoes at what they thought was an old Argentine sub, but only ended up hitting whales. "The British fleet was terrified of this thing," he said.

On the Narwhal's armaments, Heginbotham said the boat, a reverse-engineered Dutch Zwaardvis submarine brought up to speed with modern-day improvements, can likely carry at least 20 torpedoes, which could potentially sink "a lot of ships," especially if they come in an invasion fleet.

One major difference between torpedoes and missiles, Heginbotham said, is that torpedoes launched from under the sea do not expose the location of the attacker.

"You have no idea where it's fired from, all you do is you see a ship blow up," he said.

This, he said, requires enemy forces to establish a search zone for the attacker, and the MK-48 torpedo, for example, has an average range of 40 kilometers, which means the enemy would have to search within a 40 km-radius, or if the torpedo hits one side of a ship, it will narrow down the search zone to half that circle.

Guermantes Lailari, a Taiwan Fellow and visiting scholar at National Chengchi University, drew attention to submarines' surveillance and reconnaissance capabilities, likening them to undersea "sentinels" that monitor the activities of Chinese submarines, surface ships, and maritime militia around Taiwan.

In the event of a blockade by People's Liberation Army (PLA) ships, Taiwan could potentially deploy submarines, for example, in waters off the Port of Kaohsiung to ensure that Chinese military vessels will not block that channel so that a shipping lane will stay open, said Lailari, a retired U.S. Air Force lieutenant colonel.

Just as Japanese submarines typically operate in waters close to Japan, Lailari said, Taiwan's diesel-electric subs stay in waters around Taiwan, where they could try to "choke off any PLA Navy ships, for example, an aircraft carrier or even a submarine coming from Hainan Island out to the Pacific and to the North to the Miyako Strait.

Joint deterrence force

Asked whether Taiwan, U.S. and Japanese submarines could cooperate and form a joint deterrence force, Heginbotham said such an operation is "absolutely" viable, but requires the three sides to practice and establish their respective hunting area during peacetime.

Due to the high risks during war, submarines cannot communicate with each other when they cross paths, and once a submarine sees another it will attempt to shoot first lest it is attacked, Heginbotham explained.

As such, he said, each nation involved in a joint submarine operation should be assigned a hunting area and an independent lane in and out of that area, so "they will be deconflicted with one another such that those submarines should never meet." That way, when a submarine detects another submarine, it does not have to guess whose it is and can quickly shoot at it.

Lailari agreed that U.S. and Japanese subs could potentially work with Taiwanese subs during a Taiwan contingency, as the U.S. and Japan have an interest in ensuring Taiwan's security.

In that scenario, Lailari said, Taiwanese subs could conceivably guard the Bashi Channel and waters at the northern end of the Taiwan Strait to monitor and sink any Chinese submarines that try to get out and threaten the U.S. fleet coming to Taiwan's aid.

At the same time, Japan might deploy their subs and anti-submarine warfare vessels in the Miyako Strait, as well as near the Senkaku and the Yonaguni islands to prevent PLA ships from entering the Pacific, he said, adding that this would completely cut off the PLA Navy's access to the Pacific and offer protection for U.S. fleets.

Vulnerable in port

However, submarines are not without weaknesses, one of which is that they are "vulnerable in port," Heginbotham said.

Taiwan has to build a sturdy submarine pen or store them in a cave by the sea, to prevent them from being easily destroyed by PLA missiles when they are on stand-by or surface to refuel.

In the late 1980s, around the time the two Zwaardvis subs Taiwan contracted the Netherlands to build returned to Taiwan and began their service, Taiwan launched the "Antung Project" to build a submarine cave off the shore of Shoufeng Village, Hualien. The project was eventually shelved due to locals rejecting the amount offered by the government to expropriate their land for the project and the Dutch Cabinet rejecting Taiwan's order to purchase six more subs over Chinese political pressure.

According to Defense Minister Chiu Kuo-cheng (邱國正), Taiwan's current fleet of submarines is homeported at the Tsoying Naval Base in Kaohsiung.

Moreover, Heginbothem said the rate at which the battery in diesel-electric subs is depleted is "exponential" to its speed, which may pose challenges when they have to operate at high speeds, for example, when being pursued by enemy ships or aircraft.

Using a Soviet Kilo-class submarine as an example, Heginbotham said that these boats can go for 170 hours at a speed of two knots, but will last less than an hour if they are moving at a high speed of 22 knots before they have to surface to recharge.

While the Narwhal is likely to perform better than a dated Kilo-class submarine in terms of battery life, the principle is exactly the same, he said.

Land-based anti-ship missiles

Crucially, Heginbotham said, from the perspective of anti-ship warfare, land-based Harpoon anti-ship missiles only cost a small fraction of the price of a torpedo launched from the Narwhal, given the boat's high cost of NT$49.3 billion (US$1.53 billion), meaning the Narwhal will not be as cost-effective as land-based anti-ship missiles at sinking ships.

Therefore, Heginbotham said, if he were allocating the Taiwanese Navy's budget, he would spend half of it on buying anti-aircraft and land-based anti-ship missiles, the latter being more cost-effective and a better option for targeting surface ships than submarines.

In contrast, Lailari said he would not spend the majority of the Navy's budget on anti-ship missiles, because the launching platforms, including vehicles, aircraft and ships, will be targeted by the PLA, which will strike them to "prevent those missiles from ever being fired."

Most PLA ships nowadays are equipped with anti-missile systems, which can shoot down Taiwan's anti-ship missiles, he added.

If the PLA lands on Taiwan, it will mean Taiwan's land-based missile systems have likely been destroyed, but submarines can continue to operate and sink ships that are trying to replenish the PLA military on the ground, he said.

"These are the reasons why it's important not to try to focus on one capability to solve everything. You need to have multiple capabilities to solve the problem and make it much more difficult for your enemy to try to conquer you," he said.

Limited submarine fleet

Michael O'Hanlon, director of research in foreign policy at the Brookings Institution, meanwhile, said submarines are best for finding submarines, and even if a second Narwhal-class sub is finished in 2027 as hoped, Taiwan will still have too few to make a huge difference in its anti-submarine warfare (ASW) against the Chinese submarine fleet.

Taiwan currently has two combat-ready Zwaardvis submarines, which are 35 years old, and the indigenous Narwhal, which is not expected to come into service until 2025. However, it hopes to grow the fleet to 10 boats by building seven more Narwhal-class subs.

According to estimates by various sources, the PLA Navy currently has between 56 and 66 submarines.

O'Hanlon said Taiwan would do "at least as well" to invest in other relevant capabilities: ASW surface ships, mine warfare ships, coastal batteries with antiship missiles, deployable minefields, and stockpiles of key goods to help it weather an attempted Chinese blockade.

"I think there are better ways to threaten surface ships, like helicopters with antiship missiles aboard," he said. While saying that he would not object too strongly to Taiwan funding submarines, O'Hanlon noted he "just don't think it's the best use of Taiwan's defense money."

Commenting on the size of Taiwan's submarine fleet, Lailari said the National Chung-Shan Institute of Science and Technology, Taiwan's state-run weapons developer, is expected to complete an uncrewed underwater vehicle (UUV) under the Hui Lung (慧龍) Project by year-end.

The midget sub is equipped with torpedo tubes and a sonar system and can operate independently or alongside full-sized submarines in a similar fashion to the U.S. Air Force's wingman concept, which sees drones flying in formation with fighter jets and other aircraft, providing defensive capabilities, he said.

If Taiwan decides to produce 10 to 20 Hui Long midget subs, it will greatly bolster the country's submarine force, he said.

"It would be amazing if Taiwan was able to get the Hui Lung to operate in conjunction with eight submarines. So it can basically double or triple underwater capability with this smaller submarine," he added.

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