Since the early days of the Cold War, nuclear submarines have been one of the U.S. military’s most important advantages. Able to approach an opponent’s coast undetected and to attack without warning, submarines underpinned U.S. leaders’ threats to stop a Chinese invasion of Taiwan or neutralize Russia’s ballistic missile submarines. However, the era of unrivaled U.S. undersea dominance is ending. Exploiting new technologies, the inherent limitations of submarines, and their home team advantages, China and Russia are fielding new anti-submarine warfare systems and techniques that will prevent unfettered U.S. undersea operations unless the Navy embraces dramatic changes in how it fights.
As in nearly every other area of modern life, technology is driving this new era in undersea warfare. Advancements in material science, signal processing and acoustic modeling are enabling two major shifts in how opponents such as China could find and attack U.S. submarines. First, low-frequency active sonars are now small enough to be towed by ships or uncrewed surface vehicles and can detect submarines at ranges of 100 miles or more. By using active sonar — which bounces sound off submarine hulls, rather than listening for the noise they generate — these systems obviate the billions of dollars spent on submarine sound silencing during the last half-century.
The second major technology trend is the proliferation of seabed sensor arrays by governments, universities and militaries. The U.S. Navy pioneered this approach with its SOSUS arrays during the Cold War. But while SOSUS relied on cutting-edge military technology, today commercially available sensors are widely deployed around choke points and U.S. submarine operating areas like the South China Sea. Although some of these systems are notionally intended to support oceanographic and biological research, China’s leaders have characterized them as part of an “Undersea Great Wall” that could detect and track U.S. submarines.
But new sonar technologies alone will not make the oceans transparent. U.S. submarines remain the world’s quietest and their crews can operate in ways that reduce their detectability to active sonars. The challenge becomes maintaining this stealth when competition turns to conflict. If U.S. submarines begin launching missiles or torpedoes, they could be detected by sonars undersea or radars on the surface, providing Chinese maritime patrol aircraft and warships with targets for depth bombs, torpedoes and anti-submarine rockets. Facing the prospect of sustained prosecution, U.S. submarine crews may need to cut short their operations and evade until they can regain their stealth.
With their speed, stealth and torpedo countermeasures, U.S. submarines are likely to evade even sustained attacks by Chinese forces. However, they will be largely marginalized from the fight. During World War II, U.S. and allied navies used this same approach against German and Italian U-boats. After losing hundreds of thousands of tons of shipping each month early in the Battle of the Atlantic, by mid-1943, Allied convoys were crossing largely unmolested, despite nearly triple the number of submarines being at sea compared to 1940. Instead of being able to closely approach for attacks, U-boats were kept on the run by escort ships and aircraft that scored surprisingly few kills.
Fighting Into the Bastions
Avoiding the fate of German U-boats will require the U.S. undersea force to adopt concepts developed by aviators to suppress and defeat air defenses. Fighting into enemy airspace demands jammers to overwhelm sensors, decoys to confuse fire control systems, and anti-radiation missiles to destroy radars. Without these capabilities, whole areas of airspace can be denied to an attacking force, as the war in Ukraine has shown.
During the Cold War, the Soviet Navy deployed anti-submarine warships and aircraft around the Arctic waters of the Barents Sea and White Sea to protect the areas where its undersea forces train and its ballistic missile submarines patrol. These bastions were essential to Soviet strategy, which depended on Moscow’s attack submarines to threaten the U.S. coast while Soviet ballistic missiles submarines sustained a survivable second-strike nuclear response. Today, bastions in the South China Sea and Barents Sea continue to hold a central place in Chinese and Russian strategy, respectively. For China, its near seas are also where conflict is most likely to emerge with Taiwan, Japan or China’s southeast Asian neighbors.
The acoustic superiority of U.S. submarines has given them unfettered access to Chinese and Russian bastions that in wartime could be decisive. Going forward, U.S. submarines will increasingly need to fight their way into these bastions by relying on a team of ships, aircraft and uncrewed vehicles, rather than the lone-wolf tactics honed through decades of operations during the Cold War and since.
The characteristics needed to protect offensive undersea operations can also help redirect the Navy’s faltering uncrewed vehicle development efforts. For example, operations against sensors on the sea bed or floating in the water require precise targeting data developed through extensive deep-water surveys. The Navy’s now-paused Snakehead large diameter uncrewed undersea vehicle would have provided those qualities, but the service could restart the program using one of several commercially-available vehicles.
The Navy’s other uncrewed undersea vehicle classes also could be refocused on offensive undersea missions. The new Lionfish small vehicle should be oriented toward decoy and jamming operations, where they could have an immediate impact on the confidence of Chinese leaders in the People’s Liberation Army Navy’s ability to control the near seas. Able to be launched by nearly any crewed or uncrewed vehicle in the U.S. Navy, Lionfish vehicles could be quickly deployed in conflict or used in peacetime as part of responses to China’s gray-zone activities.
Larger vehicles also should have clearly-defined use cases to bound their requirements. The Navy’s new Razorback medium uncrewed undersea vehicle program, designed to be launched and recovered from submarines, should focus on minehunting. Potentially the most effective way to keep U.S. submarines out, mines could neutralize the U.S. undersea advantage. With a vehicle able to map out safe routes through minefields, U.S. submarines could get back into the fight. On the offensive side, the Navy has noted its Orca extra-large vehicle program will use minelaying as its baseline mission.
Along with cyber and space, undersea warfare is one of the enduring asymmetric advantages that underpin U.S. conventional deterrence. Adversaries such as China and Russia recognize this and are mounting creative strategies that exploit emerging technologies to keep U.S. submarines away. Silence and skill at lone-wolf tactics are no longer enough. The U.S. Navy will need to build a team for undersea superiority that uses noise, rather than avoiding it.