Imagine a world in which the oceans hide nothing. Cheap sensors are deployed all across and below the water. Swarms of unmanned undersea, surface, and aerial vehicles rove in search of adversaries. Governments can see everything that happens. Nuclear-armed submarines that once hid in the vastness of the ocean would be revealed. What does this mean for the sea-based nuclear deterrence and second-strike reliability? And how should states respond?
Greater ocean transparency changes the character of submarine deterrence, but does not eliminate key advantages. In particular, ocean transparency shifts the competition from hider-finder to find-chase-kill. Instead of relying on stealth, submarines will need to emphasize speed and self-defense, including manipulating adversary sensors and deploying sophisticated submarine decoys.
A broad range of emerging technologies is reducing the ocean’s opacity. Unmanned undersea vehicles offer cheap platforms for nanotechnology and 3-D-printed sensors and antisubmarine weapons. Machine learning and big-data tools enable the analysis of this data. At the same time, the proliferation of aerial drones and commercial satellite imagery allow improved intelligence collection on activity at submarine ports.
These technologies reinforce one another. . Improved autonomy allows better machine vision, faster decision-making, and more complex behaviors. More autonomy means less need for potentially disruptable human control. Additive manufacturing means cheaper, more customizable drones. Autonomy will allow drones to work together in swarms, coordinating among numerous systems, allowing much more efficient and broader searches. Heterogeneous swarms could include surface, aerial, and other undersea drones to form a massive antisubmarine drone network.
Of course, the ocean will not become transparent overnight; some of the necessary technologies are barely even concepts and there are significant challenges. Distributed sensors will generate massive amounts of information. If states cannot effectively handle it, they will risk seeing submarines that do not exist while missing those that do. Further, swarming may also increase the vulnerabilities to information attack through disruption of interdrone communication. Power and undersea communication will likely be a challenge too, though swarms could be linked to a support vessel to recharge and geo-locate.
Most likely, transparency will grow as these technologies mature and are fielded at scale. And true transparency may never occur. But even a significant reduction of the ability of submarines to hide poses challenges for nuclear deterrence.
The Most Survivable Leg of the Triad?
A more transparent ocean would pose a significant risk to the nation’s second-strike nuclear capability, at least as currently conceptualized. The second-strike capability maintains a credible threat to retaliate with nuclear force in the event of an adversary’s large-scale nuclear bombardment. The U.S. nuclear submarine force is usually considered the key component of U.S. second-strike capability, because of the ocean’s vastness and the limited ability of sensors to track all subs all the time.
If sensor technology coupled with other military capabilities overcomes this challenge, submarines will lose much of their stealth. An adversary could launch a successful strike without fear of retaliation, because each nuclear submarine could be targeted and destroyed. Even without complete transparency, a window may open in which an adversary has enough awareness to risk a first strike.
Thankfully, these risks are unlikely because the hider-finder model of submarine warfare is incomplete.
Find, Chase, Kill
Even in a transparent ocean, states must bring weapons into range to destroy nuclear submarines to a retaliatory launch. Submarine warfare comprises three stages: find, chase, and kill.
Find: Locate an adversary submarine in the vastness of the ocean. Even in a future fully transparent ocean, finding submarines would not be trivial. Sensors must be replaced or moved. Drone and manned searches must be coordinated, platforms maintained, and adversary countermeasures mitigated. Ocean data must be collected, stored, and processed. Processing challenges mean transparency may be significantly delayed. States must establish the training, doctrine, and organizational capability to manage these systems effectively.
Chase: Bring weapon systems within range. Even if an adversary’s nuclear-armed submarine can be located, assets must get close enough to kill it. Submarines deployed near adversary territory will be easier to catch, but their range and mobility remain an advantage compared with land-based missiles and aircraft.
Kill: Use weapon systems to cause sufficient harm to the submarine to disable or destroy it. For nuclear submarines, kill must occur before the submarine can launch a retaliatory nuclear strike. Failure means potentially devastating destruction. Perceived risks of failure may prevent an attempt in the first place.
The framework can be useful at multiple levels. States can be assessed based on their military’s overall ability to find, chase, and kill adversary submarines and prevent adversaries from doing the same. The elements of each component are highly interdependent both within and between the components. For example, find involves linking numerous, diverse sensor systems together. At the tactical level, the competition will move fluidly between different components. In chase, antisubmarine forces might: a) lose track of the submarine, shifting back to find; b) continue following the submarine (continuing chase); or c) engage, shifting the competition to kill.
The shifting nature of undersea competition demands new approaches to ensure the sea-based deterrent and second-strike remain robust. To offset greater ocean transparency states could:
- Move Faster: Designers must improve submarine speed. Faster submarines make it easier to escape adversary antisubmarine assets. Because transparency likely will come with processing and analysis delays, faster submarines create more uncertainty on the submarine’s location. In an actual attack, higher speeds might enable nuclear submarines to buy enough time to launch a retaliatory nuclear strike.
- Shoot Farther: Improve submarine-launched ballistic-missile range. Increased range allows nuclear submarines to increase the area over which they can threaten an adversary. Find and chase would become more difficult. Defenders will find it more difficult and time-consuming to deploy antisubmarine assets in weapons range.
- Hide Better: The various methods of transparency will create exploitable weaknesses. For example, submarines may be designed to fool machine vision systems; and cyber, electronic, or space attack could disable detection systems. Similarly, undersea drones could serve as decoys for nuclear-armed submarines. Such “sub-sinks” would force the expenditure of more resources to find, chase, and kill nuclear submarines. An attempted first strike also would need to devote more nuclear weapons to defeating the submarine-based deterrent. An attack on a decoy would give the nuclear submarine more time to flee or launch a nuclear strike.
- Fight Harder: Navies can explore new ways to defend nuclear submarines and counter antisubmarine capabilities. Drone sub-sinks and other drones may also help defend nuclear-armed submarines from conventional attack. Drones could be equipped with defensive antitorpedo systems and offensive antisubmarine weapons. To ensure nuclear deterrence, defensive systems only need to create enough survivability to allow a nuclear retaliation. Investments in information warfare capabilities such as jammers and directed-energy weapons would also help counter some adversary drone systems.
A transparent ocean does not mean the end of a sea-based second-strike capability. Every innovation can be countered. Improvements now can help ensure second-strike remains reliable into the future.