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Dr. James Holmes: The Naval Diplomat - 19FortyFive

Will Swarms of Underwater ‘Drones’ Make Submarines Obsolete?

Drone Swarms Submarines
The Navy's newest and most advanced submarine, Pre-Commissioning Unit (PCU) Virginia (SSN 774) moved out doors for the first time in preparation for her Aug. 16 christening. Photo courtesy Electric Boat. (RELEASED) For more information go to:

Every now and again the idea that ultramodern technology will someday render the oceans and seas transparent—and expose submarine fleets to detection, tracking, and targeting—comes into vogue. I’ve dabbled in this commentary a time or two myself. Attempting some foresight is worthwhile even though none of us can do better than gaze through a glass darkly into the future.

A recent variant of that idea holds that cheap, ubiquitous, networked undersea craft plying the depths in conjunction with sensors strewn about the seafloor could hunt down subs—even if the laws of physics continue, more or less, to confound efforts to peer into the brine. Now, this is plausible. Dave Makichuk has the latest over at Asia Times, reporting on expert opinion prophesying that swarms of unmanned underwater vehicles (UUVs) may cost submarines their “stealthy edge” by midcentury.

Almost as worrisome, the latest trends in anti-submarine warfare threaten to further erase the boundary between peacetime and wartime seafaring. Makichuk notes that even ostensibly civilian craft such as fishing trawlers could operate anti-submarine swarms. If a hostile force stuck at a drone mothership that looked like a commercial ship innocently plying its trade, the onus would fall on that force’s commanders to justify their apparent lawlessness. The aggressor could portray itself as the aggrieved. In short, gray-zone operations—paramilitary or nonmilitary ships doing militarily relevant things—are coming to the netherworld beneath the waves.

Oh, joy.

Leaving aside the gray-zone dimension for another day, my take on these developments goes something like this: undersea combat will come to resemble air combat in important ways. The ocean depths and the atmosphere are both three-dimensional realms, affording submariners and aviators freedom to maneuver. That’s intrinsic to the subsurface and aerial domains. But water is a forbidding medium by contrast with air. It distorts or blocks emissions of all kinds. Variations in temperature, pressure, and salinity have a way of bending sound in perverse ways, obscuring a boat’s whereabouts, or creating layers within the water column that mask its presence altogether.

If some combination of new technologies and operating methods makes the sea a medium more hospitable to sensors, though, sub crews will have to alter their tactics, techniques, and procedures—perhaps radically—to survive and thrive. They should study air warfare among other things. Airmen have to cope with a variety of sensors, from radar, to infrared search and track systems that seek out heat signatures, to electronic-warfare detectors and countermeasures of all sorts. UUV swarms could represent a partial counterpart to the dense array of anti-air sensors fielded by modern combatants.

If this all comes to pass, the implications for strategy, tactics, and submarine design could be profound. With regard to maritime strategy, it seems doubtful that navies will scatter UUVs and kindred devices throughout all of the seven seas. That’s a vast volume of water to monitor. Newfangled technologies won’t be that ubiquitous or that cheap, while a worldwide network of sensors would presumably be unwieldy to manage even if affordable. Sub hunters will be more selective, sowing fields of networked sensors at key nautical nodes such as the approaches to an antagonist’s seaports, or at “focal areas” such as straits or other narrow passages where shipping must converge to cross from one body of water to another.

If so, getting safely from home port to relatively safe operating grounds such as the Central Pacific could pose a stiff challenge. For example, it might be necessary to assign escorts to nuclear-powered ballistic-missile submarines (SSBNs). Attack submarines, possibly operating in concert with unmanned swarms of their own and with surface and airborne anti-submarine forces, would fight off hostile craft and clear a temporary corridor to the high seas—much as bombers may need fighter escorts to traverse heavily contested airspace. The same would be necessary in reverse when returning to port from patrol.

No longer could SSBNs simply get underway and vanish into the depths, as has been common practice since the dawn of the atomic age.

Tactics, too, could undergo wrenching change. Submariners craving entry into contested zones might have to resort to active measures to suppress fields of enemy sensors and UUVs rather than assume they can slip into these zones unnoticed. Here again, the silent service would profit from studying air-warfare tactics for suppression of enemy air defenses, offensive counterair, and the like. Submariners should no longer assume deep water is theirs to command. It is no one’s preserve—just as no one rules the sky for long in peer-on-peer conflict absent hard fighting.

Aviators’ past and present could be submariners’ future. Submarine-force overseers should essay some foresight of their own now, thinking ahead about how to adapt the culture within the force to an operating environment where concealment is far from a sure thing. A cultural revolution within the service could mean inculcating traits in officers and enlisted sailors that are more reminiscent of fighter pilots than of submariners of old.

And lastly, ship design. Despite occasional hooplah, chances are the sea will not become completely transparent anytime soon. Nevertheless, technological advances may compel subs to rely on a mix of active and passive measures rather than depend solely on passive defenses—quieting to evade acoustic detection, in other words. If so, they will come to resemble stealth warplanes. Stealth is helpful; it is not an invisibility cloak. As air defenses have advanced, aircraft designers have taken to outfitting stealth jets like the F-35 joint strike fighter with elaborate electronic-warfare suites to help them elude detection or fend off assault.

Submarine designers should embrace the same philosophy.

Are these developments cause for despair? No. The U.S. Navy clearly has some learning and reequipping to do in order to cope with this brave new world. But what works for the Chinas and Russias of the world could work even better for the United States. Look at your map. American ships of war enjoy free access to the Atlantic and Pacific high seas by contrast with Chinese ships trying to make their way into the Western Pacific or Russian vessels bound for the Atlantic, Pacific, or Arctic oceans. American weaponeers can fashion UUV swarms of their own to compound opponents’ access dilemma—much as they rigged a sensor array across the Greenland-Iceland-U.K. gap to detect Soviet subs during the Cold War.

The macro point is this: interaction is a timeless facet of strategic competition and warfare. It is far from unusual for competition to seesaw back and forth as the competitors innovate and counter-innovate in pursuit of strategic advantage. In fact, it’s the rule. Strategic competition with China and Russia will be no different.

The coming age of great-power strategic competition promises to be stressful, including for mariners who prowl the deep. The end times are not nigh.

James Holmes is J. C. Wylie Chair of Maritime Strategy at the Naval War College and a nonresident fellow at the University of Georgia School of Public and International Affairs. The views voiced here are his alone.

Written By

James Holmes holds the J. C. Wylie Chair of Maritime Strategy at the Naval War College and served on the faculty of the University of Georgia School of Public and International Affairs. A former U.S. Navy surface-warfare officer, he was the last gunnery officer in history to fire a battleship’s big guns in anger, during the first Gulf War in 1991. He earned the Naval War College Foundation Award in 1994, signifying the top graduate in his class. His books include Red Star over the Pacific, an Atlantic Monthly Best Book of 2010 and a fixture on the Navy Professional Reading List. General James Mattis deems him “troublesome.”



  1. Harry_the_Horrible

    June 11, 2021 at 10:58 am

    Some thoughts.
    The submarine drones will have limited range so they will require tenders to launch, recover, and service them.
    They will also require a high degree of autonomy – they have to be able to seek out engage an enemy using their own internal resources.
    Palletized drones will have a huge potential for surprise attacks. Merchant ships could carry them to foreign shores and simply drop them overboard. They could immediately begin operations or they could wait on a timer or signal. Either way, a nation could find its port areas infested with drones attacking their shipping or destroying port facilities.
    They could also be air-dropped.

    The tenders will represent a potential vulnerability.
    Are we going to trust the drones to make decisions on target selections and attacks?
    As the writer pointed out, how will we identify and deal with ‘civilian’ vessels supporting or controlling drone swarms?

  2. Matt Musson

    June 14, 2021 at 4:35 pm

    I can envision limpet like drones that attach to the skin of a submarine and broadcast tracking and targeting information in response to an IFF query.

    But, drones that can loiter for years in salt water, with the power to puncture a submarine hull are technically more challenging than they seem at first glance.

  3. Duane

    June 16, 2021 at 10:11 am

    Just another instance in the age old battle between offensive weapons and defensive countermeasures. Arrows and spears vs. armor on soldiers … trebuchets and cannon vs. the walls of forts and castles … bombers vs. fighters and AA fires.

    As the author says, however, the underwater realm is an extremely challenging one, and the environment necessarily entails very high costs to operate within, whether offensively or defensively or both. Consequently, the US Navy has the world’s greatest and most capable array of assets for the undersea realm, and nobody else today can top it because nobody else can really afford to top our assets.

    That is not to say that neither China or Russia will EVER top our assets, but we have a humongous head start on them, and we aren’t sitting on our laurels either – they’re not tail chasing a stationary target.

    As long as we keep investing in hardware, software, and in training and tactics we should be able to maintain our mastery of the undersea world. The danger is complacency and underinvestment.

    Unfortunately, our carrier mafia and AEGIS mafia suck up way too much of our naval budgets that would be far better spent on submarine technology, land based aircraft, and land based countermeasures (like antiship missiles). Our surface navy today is built to fight a 1990s war against jihadis in pickup trucks with AK-47s, not a modernized PLAN with subs, nukes, a large surface warship fleet, and vast numbers of antiship missiles … and are in the process today of lofting a vast array of LEO microsats that can track the location and course of every single ship on the surface of the world’s oceans 24/7/365 (which, by the way, we’re lofting too!). All surface navies, both sides in any major naval conflict, are ultimately good only as future artificial reefs and naval graveyards. Only subs and land based aircraft can survive and win a mid-21st century naval war.

    Winning a naval war is no longer about ships … it is about destroying your enemy’s ships with whatever tools you can bring to the fight.

    US Grant understood in the Civil War, as all the other Union generals did not, that to defeat an enemy, you have to destroy his army, not take and hold dirt, or his opponent’s capital. To defeat the Confederacy Grant knew he had to draw out Lee’s Army of Northern Virginia and destroy it piece by piece, and not take Richmond.

    Defending surface warships is like defending dirt – it wins you nothing. To defeat the Chinese requires the utter destruction of their navy. And that is best done by subs and land based aircraft.

  4. Harry_the_Horrible

    June 18, 2021 at 1:24 pm

    @Matt Musson
    I am pretty sure that subs can be configured to detect any parasite that attaches to the hull. Changes in hull conductivity, etc.
    They’re more worried about drones tailing SSBNs and similar issues.
    Which brings up some interesting questions: While I am sure that destroying someone’s drone within our national waters (or airspace) is lawful, what about in international waters?

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