Surface ships are of course visible to an enemy from miles away, most drones and aircraft are easily detectable, and ground-based weapons such as missile launchers and interceptors can be seen by satellites. This means that the Chinese military will likely be aware of any prepositioned assets put in place to deter or stop an amphibious assault on Taiwan. But what about submarines? From the standpoint of undetectability, could submarines be the best way for the United States and its allies to stop a Chinese invasion of Taiwan, if they chose to intervene?

Ship and land-based sensors are now advanced to the point that it would be difficult to position warships or operate certain aircraft within striking distance of Taiwan. Therefore, China might be inclined to attempt a surprise attack when U.S. carriers and other visible assets are not within range. This, however, is where submarines and undersea drones come in.

Newer quieting technologies, coupled with the rapid acquisition of undersea drones and improved torpedoes, make attacks from the sea more likely to be successful. Should enough attack submarines and sub-launched undersea drones be operating in the vicinity, they would be less detectable and in position to attack and destroy advancing Chinese amphibious forces. 

Part of this equation is fortified by recent U.S. Navy advances in attack submarine technology that not only makes them less detectable to sonar systems but also armed with more precise and long-range weapons systems. Maritime variant tactical Tomahawks, for example, are able to change course mid-flight and destroy moving targets, allowing them in a position to attack surface ships on the move. The U.S. Navy is also developing its Very Lightweight Torpedo, expanding attack envelope possibilities. Block II Virginia-class and subsequent model attack submarines are now equipped with new underwater antennas and communications devices, engine quieting enhancements, and special coating materials to make them less detectable. While details regarding what these look like are unavailable for security reasons, U.S. Navy leaders talked about these advances years ago when the USS South Dakota Virginia-class Block III submarine emerged as a prototype. The South Dakota, and other submarines with similar innovations, are now operational. This might be one reason why the operational concepts for attack submarines have evolved to include more undersea surveillance. 

Block III Virginias also use “fly-by-wire” automated navigational controls, fiber optic cables, and more advanced Large Aperture Bow sonar systems. Attack submarines, and the drones they can launch from torpedo tubes, could operate along the high-risk island and coastal areas conducting clandestine surveillance missions while being much less detectable than a surface ship or some aerial drones. Furthermore, the U.S. Navy is making rapid progress with a growing fleet of small, medium, and large, submarine-sized unmanned undersea drones. These platforms have long endurance times and can lurk beneath the sea for weeks tracking enemy surface ships, submarines, and mines. 

In the future, it seems possible some of them could be armed with weapons, provided undersea command and control technology evolves to the point where humans can remain fully “in the loop” regarding the use of lethal force. While undersea drones can already find and explode mines “autonomously” undersea, firing torpedoes would naturally need to be managed by a human operator, per Pentagon doctrine.

As for the force itself, this may be one reason why the U.S. Navy continues to accelerate and fast-track new submarines. An attack submarine “deficit” concern has been on the radar for many years now, and Congress and the U.S. Navy now plan to build as many as three Virginia-class attack submarines annually instead of two. 

Are there enough submarines to rise to this challenge? Global Firepower says China operates as many as seventy-nine submarines while the United States operates ten fewer. This is yet another reason why many in the United States continue to call for a more accelerated pace of submarine acquisition. However, U.S. allies have submarines as well. Global Firepower lists South Korea as operating twenty-two submarines and Japan is cited as having twenty. These boats, in conjunction with U.S. Navy attack submarines, might be well-positioned to stop the People’s Liberation Army Navy, given their weapons and stealth capabilities.

Kris Osborn is the defense editor for the National Interest. Osborn previously served at the Pentagon as a Highly Qualified Expert with the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Master's Degree in Comparative Literature from Columbia University.

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