The U.S. military’s greatest strategic challenge will be aiding in the defense of Taiwan against the vast capabilities and capacity of the People’s Liberation Army (PLA) in the event of an invasion. China enjoys self-evident geographic advantages in a potential conflict: Its forces will always be concentrated in East Asia, whereas only a fraction of U.S. forces are comparably situated. Given some degree of strategic surprise, the PLA could aim to swiftly seize Taiwan and achieve a fait accompli before the United States and Taiwan could effectively respond.
The United States and Taiwan need to be able to slow, disrupt, and attrite PLA invasion forces to prevent such an outcome. The goal should be to provide critical time for more U.S. firepower to be brought to bear, and to reduce the number of PLA forces that need to be either targeted en route or defeated at the water’s edge. Naval mines are such a capability, complementing various other weapons. This is not a new idea: There have been numerous writings on the need for Taiwan to develop a “porcupine” strategy to make it less vulnerable to attack, and many have mentioned that mines can play a valuable role.1 Others have focused on the use of mines by the United States without focusing on their use in a potential defense of Taiwan.2
Benefits of Mine Warfare
Both Taiwan and the United States already have limited naval mining capabilities, and Taiwan’s 2021 defense report briefly cites the need to employ naval mines, a goal reflected in its ongoing acquisition of four minelaying ships.3 However, the full capabilities of naval mines are underappreciated; mines’ ability to negatively affect operations can be far greater than is captured in the number of ships they damage. Limited investments in expanding the mining capabilities and capacities of both the United States and Taiwan could create challenging problems for the PLA Navy (PLAN). Ways in which robust minefields could stymie an amphibious invasion include:
• Providing intelligence. If the PLA adopts an ambiguously threatening posture, any actions it takes to counter U.S. or Taiwanese minelaying, or to assess the risk posed by the resulting minefields, would contribute to intelligence regarding its intent. During a conflict, PLA attempts to assess or clear minefields could provide advance information regarding where it intends to operate.
• Protracting timelines. A credible minefield threat requires some mine countermeasures (MCM). MCM efforts to assess and reduce risk are inherently time consuming and resource intensive. Moreover, MCM platforms generally are fragile and move slowly in predictable patterns, making them excellent targets for other weapons; their occasional destruction would inflict further delays. Even an accelerated, casualty-tolerant approach to MCM slows operations, as the attacker selects a relatively low-value ship (crewed or uncrewed) to transit the minefield while other ships wait, then sends follow-on ships to absorb additional mine hits once the first ship has succumbed.
• Disrupting coordination. To the extent that some parts of an amphibious invasion are impeded more than others, the operation’s precise choreography is disrupted. Platforms meant to protect the invasion force, as well as critical equipment and personnel, would be in the wrong places at the wrong times.
• Channelizing traffic. Ships passing through a minefield aim to adhere to a consistent, predictable path, and move slowly to avoid straying into uncleared areas. They also may not be able to assume desired configurations relative to one another for collective missile defense. This can make them easier to target with missiles and other weapons.
• Creating obstacles. Damaged ships can create collision risks if they have less than complete control over their movements, while sunken ships can create navigational hazards in the crowded operational environment of an amphibious assault.
• Impeding use of operating areas. Minefields are particularly menacing to vessels that loiter in an operating area, such as those launching aircraft, waiting to drop off or pick up loads, or conducting antiair, antisurface, or antisubmarine warfare. Loitering ships eventually will encounter any mines in their operating areas. Even very low densities of mines can therefore force ships that must maneuver within an operating area to either operate in less advantageous environments or inhibit their movements, potentially in ways that diminish their combat effectiveness. If they remain stationary for long periods to reduce the risk from mines, they become more vulnerable as fixed targets.
The PLAN’s ample arsenal of naval mines implies it respects the threat mines pose, likewise suggesting it would fear a formidable mine capability arrayed against it.4 Given ample historical cases in which naval mines have thwarted amphibious invasions, such fears would be well-founded. For example, during the Korean War, U.S. forces were planning an amphibious invasion at Wonsan, along the eastern coast of the peninsula. The use of hundreds of mines delayed the operation for so long that by the time Marines went ashore, the Army had already captured the city.
During World War I, a British-led attempt to seize Constantinople failed when naval minefields were reinforced by shore-based guns. More recently, during Operation Desert Storm, Iraqi minelaying in the northern Gulf damaged two U.S. warships. While the United States had already decided that its threatened amphibious invasion of Kuwait was a feint, mines precluded this strategy from being a viable alternative without absorbing large-scale casualties.
Taiwan and the United States can use several well-honed tactics to elevate the risk to PLA forces; these techniques can work against both thorough MCM efforts that might take days or weeks, as well as swift, casualty-tolerant approaches to MCM.
Influence mines, which typically sit on the seafloor and detonate when they sense a ship’s signatures above them, can be designed with “ship counters” that instruct them to detonate when the second, third, or n-th ship passes over them. As a result, MCM sweeping assets or low-value ships can pass through a channel and experience no damage, but subsequent, higher-value ships will. Influence mines also can be given probabilities of detonation, intermittent periods when they do not detonate, or algorithms that instruct them to detonate only in the presence of signatures for specific classes of ships.
Collectively, these techniques to make mines a little smarter can have insidious psychological effects by creating friction among commands. Once MCM forces or low-value ships seemingly have cleared a channel, but high-value ships are then damaged within it, a frustrated commander may become dismissive of anything that MCM forces say or do. Well-planned minefields can inspire bad choices of over-aggressive behavior or excessive timidity.
Other mining strategies can be useful, depending on the attacker’s anticipated MCM behaviors. Attempts by the attacker to hunt the mines (i.e., to locate them using sonar) can be hindered by designing mine shapes that look like detritus or that are designed to self-bury in appropriate environments. Putting a few moored contact mines—the classic “spiky balls” that most people envision when they think of mines—into the minefield also can protract timelines, since they require different MCM techniques from those used for influence mines.
Advantages of a Mine Warfare Defense
Three key advantages of emphasizing a mine defense of Taiwan are the desirable operating environment, low technological risks, and the ability to impose costs on the PLA. First, the shallow waters of the Taiwan Strait are easily mined.5 Second, since all the mining technologies mentioned date back to the Cold War or earlier, there are minimal technological risks in developing similar mines. The correspondingly low costs of development and the lack of a need for specialized materials contribute to the low investments necessary to ramp up mine production. Expanding mining capabilities and capacity would also be cost imposing, since the cost of MCM is consistently far greater than that of mining; it is much cheaper to make and drop nefarious objects in the water than to neutralize them.
For example, the two mines that damaged U.S. warships during Desert Storm in 1991 cost $1,500 and $10,000, but collectively inflicted $21.6 million in damage.6 Each mine costing thousands or tens of thousands of dollars can inflict millions of dollars in damage on a sacrificial ship or be eliminated by fastidious MCM forces whose total costs—including acquisition, maintenance, personnel, and training—are in the hundreds of millions or billions of dollars.
Acquiring a few thousand mines might cost in the tens of millions of dollars, plus low maintenance costs. Pushing them into the sea from surface vessels, which may be commercial ships fitted with mine rails, also is relatively inexpensive. The cost imbalance remains compelling even if only some of the mines are in channels the PLA aims to clear, each sacrificial ship can absorb several mine hits before expiring, or each MCM platform can eliminate dozens of mines in a given operation. Developing large numbers of highly capable PLAN MCM personnel would require not only substantial investments, but also many years or even decades for them to gain experience.
Other, more advanced technologies could be employed in parallel to create additional risk for PLAN forces and stymie their MCM efforts. Mobile mines developed during the Cold War had the ability to periodically relocate themselves, enabling a minefield to “self-heal” by creating a hazard in a previously cleared channel. During the Cold War, the United States developed the encapsulated torpedo (CapTor) mine to target submarines: A sensor on the mine that detected a submarine would launch a torpedo to destroy it. The result was that each CapTor mine could damage submarines over a much wider area than an explode-in-place mine.
While both mobile mine and CapTor technologies are well-established, they are also costlier than stationary mines that simply explode in place. However, they could be used for specialized purposes, such as securing straits through which Chinese submarines might pass en route to the open ocean. These technologies could also potentially be updated, given the advent of uncrewed undersea vehicles (UUVs). UUVs potentially could stretch the concept of what a mine is by lingering in key waterways and automatically launching torpedoes when their sensors detected approaching ships. More prosaically, UUVs also could clandestinely reseed minefields.
Laying the Minefields
U.S. and Taiwanese forces could use several different types of minelaying platforms.
• UUVs and (if available) submarines could provide a clandestine minelaying capability, one suitable for laying mines near China’s own ports.
• Aircraft or uncrewed aerial vehicles (UAVs) could enable rapid distribution of mines in multiple areas in a particularly demonstrative way, which could help to deter a conflict.
• Surface ships or uncrewed surface vessels (USVs) could provide high-volume mining, again with some degree of demonstration. The ships could include commercial vessels, which could use cranes or easily installed mine rails to drop mines into the water. Surface ships would provide more ambiguity than aircraft about precisely where mines had been dropped: While a vessel’s path can be tracked from above, continuous scrutiny is needed to determine when it drops something in the water, since the main signature is only an ephemeral splash. Given the high capacities of vessels, some dropped objects also could be cheap decoys, which would further confound both observation of the minelaying operation and any subsequent PLA efforts to map the minefields.
U.S. forces could store mines and decoys in various regional depots, alongside minelaying vessels and aircraft. Recurring minelaying exercises in the Taiwan Strait that used decoy mines would contribute to training, deterrence, and littering the bottom with decoys that would make it harder to hunt actual mines in a conflict. Taiwan and/or the United States also could maintain some minelaying vessels with mines on board and have them periodically roam the Taiwan Strait for deterrence. The PLAN also would have to speculate whether UUVs and submarines armed with mines were in the Taiwan Strait at any given time.
In the event of a serious war threat, U.S. and Taiwanese forces could load large numbers of mines onto aircraft and vessels that would then operate in the Taiwan Strait to send a message to Beijing. Any attempts by PLAN forces to interfere with their movements would be indicators of Beijing’s intent and visible provocations that could help to shape international perceptions.
In a crisis, dropping objects in the water—decoys or real mines—could help shape Beijing’s perceptions. If real mines were used in the face of an impending invasion, the United States and Taiwan would then publicly alert mariners to the risk posed by these minefields, in accord with the Hague Convention. The mines could be designed to self-sterilize after an extended period—perhaps six months or a year—during which time stocks could be rebuilt. Once the crisis had passed, the mines also could be cleared by Taiwanese and U.S. MCM forces.
To enable this strategy, both the U.S. and Taiwanese navies should invest more heavily in naval mining, beginning immediately. The anemic U.S. mining program currently lacks any mines that are deployable from surface vessels. This greatly limits minelaying capacity, particularly given copious other demands for the submarines and aircraft that can lay mines. Constructing large numbers of diverse mines using inexpensive 20th-century technology is straightforward, as is retrofitting a variety of commercial platforms to lay them. Decoy versions of mines also should be made in large numbers, then used in training and during exercises, including in the Taiwan Strait itself.
Mines as Part of a Porcupine Defense
If China attempts to invade Taiwan, its formidable geographic advantage and its vast arsenal of missiles will diminish the U.S. ability to respond effectively. The extensive use of naval mines could help to slow, disrupt, and attrite Chinese forces, providing critical time for both Taiwan and the United States to prevent a fait accompli.
Looking beyond the raw number of ships damaged, naval mines can hinder an amphibious assault by interfering with the critical synchronization required. By channelizing and slowing ships, mines can make them more vulnerable to complementary forms of attack. Relatively inexpensive mines also can impose disproportionate costs on an adversary, both in terms of the long-term investments required to effectively counter them and during an actual operation.
Perhaps most important, enhanced mining capabilities can inject doubt into China’s calculus. To the degree that a robust mining capability diminishes the PLA’s confidence in its ability to swiftly capture the island, that trepidation can help deter conflict. Beijing’s aspirations to acquire Taiwan likely will not diminish. China will be more likely, however, to postpone such an attack indefinitely, rather than exploiting or creating possible crises to initiate an invasion. An approach to defending Taiwan that involves more extensive use of naval mines also can diminish China’s confidence in its ability to negate U.S. power, creating a healthy consternation that can contribute to enduring peace.
1. See, for example, James Timbie and ADM James O. Ellis Jr., USN (Ret.), “A Large Number of Small Things: A Porcupine Strategy for Taiwan,” Texas National Security Review 5, no. 1 (Winter 2021/2022); William S. Murray, “Revisiting Taiwan’s Defense Strategy,” Naval War College Review 61, no. 3, Article 3 (2008); David Ochmanek and Michael O’Hanlon, “Here’s the Strategy to Prevent China from Taking Taiwan,” The Hill, 8 December 2021; and Jack Detsch and Zinya Salfiti, “The U.S. Is Getting Taiwan Ready to Fight on the Beaches,” Foreign Policy, 8 November 2021.
2. See ADM James Winnefeld Jr. and CAPT Syed Ahmad, USN (Ret.), “The Other Mine Warfare Will Work,” U.S. Naval Institute Proceedings 144, no. 7 (July 2018); Scott D. Burleson, David E. Everheart, Ronald E. Swart, and Scott C. Truver, “The Advanced Undersea Weapon System: On the Cusp of a Naval Warfare Transformation,” Naval Engineers Journal (March 2012): 57–64; CDR Timothy McGeehan and CDR Douglas Wahl, USN (Ret.), “Flash Mob in the Shipping Lane!” U.S. Naval Institute Proceedings 142, no. 1 (January 2016); Joshua J. Edwards and CAPT Dennis M. Gallagher, USN, “Mine and Undersea Warfare for the Future,” U.S. Naval Institute Proceedings 140, no. 8 (August 2014): 72–73; and Scott Pratt and Daniel E. Everhart, “Asymmetric and Affordable,” U.S. Naval Institute Proceedings 138, no. 6 (June 2012): 46–49.
3. Republic of China National Defense Report 2021, 67–68; and Timbie and Ellis, “A Large Number of Small Things.”
4. Andrew S. Erickson, Lyle J. Goldstein, and William S. Murray, “Chinese Mine Warfare: A PLA Navy ‘Assassin’s Mace’ Capability,” Naval War College China Maritime Studies, no. 3 (June 2009).
5. While more advanced and costly mines would be required in the deeper waters east of Taiwan, the risk of a PLA landing in eastern Taiwan also is much smaller than in the west. PLA forces landing in the east would be trapped in a narrow corridor between the mountains and the sea, far from Taiwan’s population centers and infrastructure. PLA forces taking that roundabout route would also be more vulnerable than comparable landing forces in the west, given greater distance from mainland-based fires and logistical support.
6. Government Accountability Office National Security and International Affairs Division, “Navy Mine Warfare: Budget Realignment Can Help Improve Countermine Capabilities,” GAO/NSIAD-96-104 (March 1996).