The United States and Allied forces countered enemy forces with their own submarine and anti-submarine capabilities in an intense undersea battle. The administration of President Tsai Ing-wen intends to spend a large sum of money and years of effort to revamp this same stealthy undersea capability for the present day as Taiwan builds its new fleet of indigenous defense submarines (IDS).
The new government has earmarked $95 million on the design phase alone for up to eight submarines. Then, there are the research, development and manufacturing costs that will expand the budget into the billions of dollars, all of which call for a cost-benefit analysis. In the indigenous submarine (IDS) fleet, Taiwan is investing in a valuable asymmetrical military capability; however, these vessels will only be able to offer limited conventional deterrence.
Taiwan currently possesses four old and tired submarines. Two of them are inoperable World War II Guppy class submarines provided by the United States; the only operable ones are two Dutch-built Zwaardvis Mk2 Sea Dragon class submarines from the 1980s. Needless to say, these older submarines are long past their operational timelines. If Taiwan does not buy or build more submarines, it will run the old models into ground and face the reality of having none left.
Submarines are a key part of Taiwan’s order of battle since submarines are difficult to detect while submerged underwater, and an adversary cannot easily attack what it cannot see. During World War II, U Boat submarines dominated the Atlantic theatre with its deadly “wolf pack” (Rudeltaktik) strategy, where they grouped together and ascended on a target by day, and hid away and dispersed each night. In the Pacific theatre, Imperial Japan’s submarines attacked Allied warships with its naval combat doctrine focused on fleet warfare. Taiwan needs such capabilities. The technical term that military strategists use in land warfare for protection against enemy observation or gunfire is “defilade.” The submarine’s advantage is that being underwater is the ultimate defilade; the best sniper perch, a kind of invisible wolf pack.
Due to its geographical size and limited military resources, it is especially important for Taiwan to pursue asymmetrical advantages by building these new submarines. Taipei cannot monetarily afford to fight symmetrically by trading 1,000 interceptor missiles for 1,000 of a potential adversary’s ballistic missiles, or 100 naval destroyers to fight against 100 of an adversary’s naval vessels. Submarines are an asymmetrical capability because one submarine can successfully engage dozens of surface vessels without being detected—a classic example of David versus Goliath. It would trade one loss for many wins, or possibly zero losses if it escapes undetected.
For Taiwan’s purposes, submarines would serve a range of valuable and traditionally risky functions such as breaking a trade blockade against the island, laying mines, targeting an adversary’s naval vessels, protecting its own surface naval vessels, like its Lafayette class frigates, covertly inserting its special forces, and more. That said, breaking trade blockages and targeting an adversary’s surface naval vessels are the most likely scenarios for Taiwan, and submarines could do it with more survivability than any other military platform. Other air or land-based platforms will reveal their position after their first shot and be quickly eliminated in a counter attack. Worse, other platforms might struggle to even take a first shot, since an adversary could more easily launch a preemptive attack against air, land and naval surface vessels.
Yet, one important limitation is that Taiwan’s submarines would have little or no deterrence capabilities—at least not in the same way that major powers equip their submarines with nuclear weapons to deter other countries from attacking. Preeminent military strategist Herman Kahn has stated that, nuclear “credibility depends on being willing to accept the other side’s retaliatory blow. It depends on the harm he can do, not the harm we can do.” Even armed with powerful conventional missiles, Taiwanese submarines would barely offer a small deterrent against an adversary. A conventional missile strike against a city is minor compared to a nuclear strike and is less effective in deterring a potential adversary’s attack. Since Taiwan does not possess nuclear weapons, its submarines would not be able to serve as one leg of an air, land, and sea nuclear defense triad like U.S. Ohio-class submarines.
The history of submarine combat operations demonstrates that submarines are an especially powerful platform because they are invisible, survivable, and serve unique asymmetrical functions within naval forces. It is understandable why Taiwan actively pursues this asymmetrical capability, though its IDS program will be a costly endeavor. The sizeable investment of $95 million for the design phase is just the beginning, and it will likely grow into the billions of dollars. In light of Taiwan’s defense requirements, submarines will play a major role in counter-trade blockades and targeting an adversary’s naval vessels. However, armed with only conventional missiles, Taiwan’s submarines will play a limited role in deterrence against unrestricted warfare. In addition to its own indigenous efforts, Taiwan should seek assistance from advanced countries with defense industries that are capable of manufacturing submarines, which will be explored in the next article of this series.
The main point: Submarines would play an important part in Taiwan’s military posture, and serve valuable anti-blockade functions, but Taiwan should also recognize the limitations of such a program, and be aware that its submarines will not be a robust deterrent against attack.
 Bud Cole, Taiwan’s Security: History and Prospects (New York: Routledge, 2006), 127.
 Gordon Williamson, U Boat Tactics in World War II (New York: Bloomsbury Publishing, 2012), 29.
 Ronald Spector, Eagle Against the Sun: The American War with Japan (New York: Simon and Schuster Publisher, 2012), 48.
 Herman Kahn, On Thermonuclear War (Princeton, NJ: Princeton University Press, 1959), 32.
 Graham Spinardi, From Polaris to Trident: The Development of United States Fleet Ballistic Missile Technology (Cambridge: Cambridge University Press, 1994), 170.