Unmanned Vessels Threaten to Undermine the Sea-Based Deterrent
The MOC
By Laurel Baker
September 27, 2024
For more than half a century, the U.S. military has relied on ballistic missile submarines (SSBNs), thought invulnerable in the ocean’s shadowy depths, to deter a nuclear attack. In theory, the nuclear-tipped missiles they carry onboard ensure that the United States always has the capacity to retaliate against a first strike. However, unmanned maritime vessels (UMVs)—particularly unmanned underwater vessels (UUVs)—are radically transforming ocean transparency, from mapping the seafloor to detecting and shadowing commercial and military vessels, including SSBNs. As UMVs proliferate, American policymakers must contemplate a day when ubiquitous sensing renders the Navy’s SSBN fleet vulnerable, altering arms control prospects, undermining nuclear risk reduction efforts, and challenging the assumptions underlying a secure second-strike capability.
Thousands of increasingly invisible UMVs crawling around the ocean present a novel strategic challenge for submarine forces. States already try (and frequently fail) to capture glimpses of adversary submarines to maintain situational awareness, foresee a first-strike set-up, or gather other valuable intelligence. UMVs enhanced by artificial intelligence (AI) may more effectively penetrate submarines’ disguises through methods like advanced magnetic anomaly detection, synthetic aperture sonar or varied sensor data integration. Reliable AI has the potential to eventually coordinate swarms of UMVs to locate and stalk SSBNs on patrol. While real-time deep-water data transmission remains a distant aspiration, a UUV could feasibly communicate via submerged energy and data transfer centers or come to the surface to relay information to other assets and back to higher headquarters. UMVs are low-cost, low-profile, high-endurance, and low-risk machines compared to conventional naval platforms. They could provide tailored tailing or form an ocean-wide surveillance net in the not-too-distant future.
UMVs still face significant technical hurdles before they strike a fatal blow to SSBN stealth and survivability at sea. First, even nimble UUVs will struggle with the same corrosive and obstacle-laden environments as all other underwater assets. Second, in addition to improving unmanned vessels’ physical fundamentals––adequate long-term propulsion and energy storage mechanisms independent of motherships or tethers––sonar packages must be more sensitive, wide-ranging, and discerning. Multiple commercial and military UMV developers in the United States and abroad are working hard to bring these technological leaps to fruition. The U.S. military would do well to start thinking about UMVs capable of tracking American SSBNs as a “when,” not an “if” problem.
Submarines are on the back foot in a race to implement superior detection and counter-detection technologies. Sophisticated SSBNs are likely to find it difficult to expose maneuverable, low-profile UUVs through traditional passive or active sonar. Passive sonar’s effectiveness is hindered by the reduced Doppler effects from UUVs’ slow speeds, great distances, and background noise. Hunting for UUVs with active sonar is almost always out of the question because doing so gives away the submarine’s own position.
Engineers will instead likely continue pursuing better ways to hide SSBNs, like more advanced noise-cancelling sheaths, ever-quieter propulsion systems, anti-UUV UMVs, sensor networks and acoustic barriers, as well as decoys, jamming, and other means of electronic warfare. But deeper dive capabilities, longer endurance, mission diversity, and affordability mean UUVs will always be able to generate innovative countermeasures faster than manned platforms, drawing ever more pervasive, tight confines around these “boomers”. Military leaders should consider whether betting on submarines’ ability to stay perpeturally ahead of UMVs’ detection techniques is financially and bureaucratically viable in the long-term, especially given adversaries’ and industry’s rate of change.
Is it possible to restrict adversaries from acquiring and fielding unmanned technologies in the first place? Regulatory solutions might gatekeep UMV technology, limit legal uses, create confidence-building measures for dual-use vessels through public-private partnerships, and establish norms of conduct through international working groups. However, these non-proliferation measures alone are inadequate, as demonstrated by the similar case of unmanned aerial vehicles, where components and other dual-use items that routinely escape export control measures. Consider also that the United States must transform and protect its own hybrid fleet while exposing its adversaries’, which disincentivizes certain domestic acquisitional and operational regulations and may complicate parallel multilateral efforts. UMV advancements are therefore as much a technical problem as a policy dilemma.
How do novel detection possibilities offered by UUVs affect the political and operational dynamics around SSBNs? One way is through arms control. Since brokered agreements are partially predicated on credible second strike capabilities, newly-vulnerable SSBNs may alter states’ calculus surrounding reductions in the the size of their ground- and air-based nuclear forces. For example, questions around whether intercontinental ballistic missiles (ICBMs) remain viable due to their mostly static locations and susceptibility to a first strike are counteracted in part by submarines’ reliable stealth. Consistently locating subs would disrupt this balance and reinvigorate concerns around appropriate force composition. Such circumstances prompt countless negotiation questions. For instance, what strategic incentives will drive the decision-making of states (such as the United Kingdom) that are largely or completely reliant on their sea-based nuclear forces for deterrence?
Another reverberation surrounds nuclear risk reduction. Deploying UUVs equipped not only to track but attack SSBNs dramatically heightens the stakes around misperceptions. Unreliable autonomy or tactical miscalculations could result in malfunctions, accidental collisions, or exposure. Moreover, the added complexity of interpreting rival UUVs’ behavior around SSBNs could lead to false alarms and subsequent escalation.
Finally, UMVs will potentially undermine the second-strike guarantee, encouraging “use it or lose it” and launch-on-warning pressures traditionally associated with land-based ICBMs. Particularly delicate moments may occur when certain countries outpace others’ UMV development, leading to highly asymmetric surveillance. In this case, allies under another state’s compromised nuclear umbrella might instigate “proliferation cascades”. Furthermore, a state with a robust submarine surveillance matrix could strategically justify preemption to neutralize a significant portion of its victim’s nuclear forces, possibly leading to the abandonment of remaining “no first use” policies and lowering the threshold for nuclear conflict. While it seems unthinkable that actors may opt into nuclear escalation, states’ individual persuasions, post-Cold War proliferation, and alliance-building complicate dyadic concepts like mutual assured destruction. How should states confront these new uncertainties in light of crumbling arms control agreements and nuclear saber-rattling?
While the sea leg of the nuclear triad is not the end-all-be-all, nuclear experts should account for technologies that challenge conventional deterrence frameworks, especially since UMVs are just one of several emerging disruptive factors that might undermine a first or second strike. Quantum computing and sensing, remote sensing enhanced imaging, machine learning, and other AI efforts spark worry. The dissemination of these technologies across the air, land, and sea complicate efforts to fortify other strategic assets. They equally provoke examination of how nuclear deterrence might evolve to discourage “gray zone” attacks, fortify crisis communication lines, and clarify an altered “escalation ladder.” Taken together, this disruptive potential represents a “Standstill Conundrum,” in which nuclear peers might confront concurrent dissolutions of their second-strike capabilities, calling into question whether arsenals should expand or relations will organically stabilize. Thus, states do not only face a “hard” strategic, but also a diplomatic problem.
UMV development and proliferation has a long way to go before oceanic transparency transforms and worries around SSBNs materialize, but make no mistake of its inevitability. Because autonomous systems and other emerging technologies are sure to become a greater part of any nuclear state’s strategic calculations, policymakers, military leaders, and international bodies must immediately reckon with UMV’s impending multiplication and their effect on the shape of future nuclear deterrence.
Laurel Baker is the 2024 Rising Expert on Geostrategy in the Rising Experts Program at Young Professionals in Foreign Policy. Currently working for Pacific Northwest National Laboratory (PNNL) as a National Nuclear Security Administration Graduate Fellow, she previously conducted research at a variety of think tanks and NGOs, including the Hoover Institution, Institute for the Study of War, The Arctic Institute, the Wilson Center, and the National Academy of Sciences. Laurel holds an MA in Russian, East European, and Eurasian Studies from Stanford University.
The views expressed in this piece are the sole opinions of the author and do not necessarily reflect those of the Center for Maritime Strategy or other institutions listed.