20,000 Drones Under the Sea

By Commander Craig Allen, USCG, and Casey Allen

In February 2017, Houthi rebels attacked a Saudi Navy frigate with an explosive-laden unmanned surface vessel. On 2 January 2018, video emerged of Houthi rebels celebrating their seizure of a U.S. Navy Remus UUV off the coast of Yemen. 1 Four days later, Russia reported that its forces in Syria had been attacked by guerrillas using what appeared to be a swarm of sophisticated, do-it-yourself aerial drones configured with bomblets, electromagnetic countermeasures, and long-range precision guidance capability. 2

The implications are clear: Nonstate actors are acquiring and weaponizing unmanned systems, and UUVs soon will join their aerial and surface-borne cousins.    

Nemo as Nemesis 

The latest “National Defense Strategy” signals a shift from the post-9/11 focus on counterinsurgency and irregular warfare toward a return to near-peer competition. Yet as the services reorient to counter the high-end threat, it would be imprudent for them to disregard the lessons of history and realign irregular forces and nonstate actors to a second-tier priority. UUVs could be used as an asymmetric weapon by a wide range of enemies, and identifying the vulnerabilities their horizontal proliferation will expose is a necessary first step to preempting their future danger. 


Drug-trafficking organizations (DTOs) are at the vanguard of nonstate actors’ ventures into the undersea domain, and they likely will be among the first to employ UUVs. Over the past two decades, Colombian DTOs developed the ability to build sophisticated self-propelled semi-submersible (SPSS) vessels to thwart surface-based detection and interdiction forces patrolling their trafficking routes. These “narcosubs” convey an estimated 30 percent of the maritime flow of drugs from South America. 3 Their low signature makes them difficult to detect, but the United States is getting better at it. 

Between June and October 2017, for example, the U.S. Coast Guard interdicted a record seven low-profile or SPSS vessels in narco-transit zones, resulting in the seizure of cocaine valued at more than $300 million. 4 Each captured vessel operator also provided a potential source of human intelligence vital for broader counternetwork operations. 

For DTOs, UUVs offer the prospect of a smuggling conveyance that is more space efficient and harder to detect than a manned vessel and that does not require an operator who might give up information in return for a plea deal. Acquiring a fleet of UUVs large enough to move the immense volume of narcotics bound for the United States could give DTOs the potential to defeat current interdiction capabilities entirely, opening up an uncontested criminal superhighway into the United States. 


With the ability to maneuver unseen until they are in position to attack, UUVs are a terrorist’s dream. Most current maritime antiterrorism and force protection measures are designed to thwart surface, not subsurface, threats. The Coast Guard, the lead federal agency for maritime homeland security, has almost no capability to detect or disrupt an underwater attack. Nor are the Department of Defense’s (DoD’s) antisubmarine warfare capabilities configured to confront UUVs already available and in development. 

UUVs could threaten the maritime transportation system that is the backbone of global commerce. Analysis of maritime vulnerabilities after 9/11 revealed that an attack that shut down a major port facility such as Los Angeles/Long Beach for even a short time would immediately disrupt the United States’ just-in-time supply chain, with reverberations throughout the world economy. An attack on multiple ports would cause catastrophic disruptions. 

To mitigate the risk, the United States and other maritime nations increased their port, waterway, and coastal security posture to provide a layered defense, to include improved surface tracking, vessel screening, crew vetting, cargo inspection, and waterside security. UUVs could circumvent most or all of those layers. 

Offshore infrastructure poses another strategic vulnerability. One example familiar to Fifth Fleet sailors is the Al Basrah Oil Terminal off the coast of Iraq, through which almost all of Iraq’s oil flows for export. U.S. and coalition warships enforced a constant security perimeter around it for more than a decade as part of Operation Iraqi Freedom before handing the mission over to the Iraqi Navy. Still, those protective measures did not anticipate an underwater attack. 

Closer to home, the United States has 175 offshore oil rigs in addition to major offshore oil and liquefied natural gas terminals to protect. One need only consider the impact of the 2010 Deepwater Horizon explosion and ensuing 5-million-gallon oil spill to appreciate the magnitude of the environmental and economic devastation a successful attack on even one platform could cause. 

Undersea network cables also present a tempting target to anyone with a desire to cause massive global disruption. In 20,000 Leagues , Nemo happens upon the first transatlantic telegraph cable, newly completed at the time the novel was published. Verne recognized what a vulnerability that cable represented. 

Today, the backbone of the internet is formed by a network of more than 200 submarine communications cables (SCCs) that carry more than 95 percent of our international communications and trillions of dollars of global commerce daily. The military operates its own network of dedicated SCCs to route classified communications overseas, although unlike commercial SCCs, the locations of these cables are closely guarded secrets. 5 In a sea full of UUVs, those locations become increasingly difficult to protect. 

Irregular Warfare

UUVs open the undersea domain to irregular actors, just as unmanned aerial vehicles (UAVs) allowed groups such as the Islamic State to take to the air. Adding UUVs to existing sea-denial weapons such as fast attack craft, mines, and antiship missiles significantly complicates the risk assessment for littoral operations. Unseen and hard to detect, they can be costly to neutralize, with clear implications for naval and amphibious mission planning. 

UUVs employed in an intelligence, surveillance, and reconnaissance (ISR) role can frustrate the ability to maneuver forces unobserved. The United Kingdom even predicts that underwater drone proliferation will make hiding its Trident nuclear submarines increasingly difficult and is debating whether it is worth recapitalizing them. 6 Clearly, a comprehensive approach to preparing for the impact of UUVs from the tactical to strategic level is a security and defense planning imperative.

Early Action on Counter-UUV

A new technology is disruptive only to the extent that it outstrips countermeasures to contain it. If Captain Nemo had undertaken his exploits a few decades later, for example, even the rudimentary antisubmarine warfare (ASW) capabilities developed during World War I would have blunted his asymmetric advantage. Anticipating a disruptive threat is critical to mitigating its impact. 

The current scramble by the military and law enforcement to counter UAVs illustrates what happens when countermeasures end up in a stern chase with an emerging threat. Although the security implications of aerial drone proliferation might have been predicted more than a decade ago, it took several high-profile incidents to kick counter-UAV development into high gear. 

As a short-term solution, the United States can advocate a nonproliferation strategy to slow the rate at which nonstate actors can acquire higher-end UUV capabilities. Such an endeavor inevitably would meet resistance from the commercial sector, and the United States would have the burden of demonstrating why the risk to global security justifies curtailing free market enterprise. Bringing Russia and China on board also would prove difficult. However, the fact that UUVs can threaten global economic lifelines and upend the state/nonstate balance of power should be enough incentive to gain a general consensus on the value of controlling access.   

But nonproliferation can only buy time. U.S. maritime homeland security and defense strategy must evolve into a modular system capable of continuous improvement by integrating new technologies as they emerge. BAE Systems, for example, builds UUVs that can be launched through existing submarine torpedo tubes to map targets using active sonar without revealing the host vessel’s position. 7 The effectiveness of these UUVs is limited, however, by the small size required for deployment from a torpedo tube. The innovation required to maintain defense-in-depth against a growing threat requires forward-thinking design that facilitates the integration of future modules capable of providing a suite of comprehensive countermeasures while maximizing long-term return on investment.  

Carrying forward hard-learned lessons from the counter improvised explosive device (IED) effort, a priority for counter-UUV efforts must be defeating networks that facilitate the threat rather than the devices themselves. The Joint IED-Defeat Office (JIEDDO) identified attacking the network as a pillar of its counter-IED strategy, and the concept later was refined and incorporated into Joint Publication 3-25, “Countering Threat Networks (CTN).” CTN doctrine seeks to create a virtuous cycle between intelligence and operations to predict enemy operations, locate and target enemy forces, and use intelligence gained from successful interdictions to guide future operations. CTN only works if the friendly network operates efficiently enough to outmaneuver the enemy network, so building an effective military-law enforcement network focused on the UUV threat now is a crucial precondition for success in the future. 

Lessons Verne’d

20,000 Leagues ends with the Nautilus trapped inside a whirlpool that is swallowing both the ship and its captain. A vortex is an appropriate analogy for the disruptive potential posed by UUVs. The race to develop adequate counter-UAV solutions is evidence that DoD’s slow acquisition process is insufficient to combat rapidly evolving technological threats. Those tasked with defending the nation and its interests cannot afford to allow an undersea threat for which we have no counter to develop. Consider the following quip by Captain Nemo, and imagine it spoken with an evil gleam in the eye: “Thirty feet below sea level, their dominion ceases, their influence fades, their power vanishes! . . . Here alone lies independence! Here I recognize no superiors! Here I’m free!”

1. Ben Werner, “ Houthi Forces Capture US Navy Unmanned Underwater Vehicle off Yemen ,” USNI News , 3 January 2018.

2. Neil MacFarquhar, “ Russia Says Its Syria Bases Beat Back an Attack by 13 Drones ,” The New York Times , 8 January 2018.

3. Christopher Woody, “ Watch the US Coast Guard Seize a Narco Sub Laden With More Than 5,600 Pounds of Cocaine ,” Business Insider , 31 October 2016.

4. “ Coast Guard Sees Resurgence of Low Profile Smuggling Vessels ,” Coast Guard News , 17 September 2017.

5. Nicole Strarosielski, The Undersea Network (Durham, NC: Duke University Press, 2015).

6. David Hambing, “ The Inescapable Net: Unmanned Systems in Anti-Submarine Warfare ,” Parliamentary Briefings on Trident Renewal, March 2016.

7. Megan Eckstein, “ DARPA, BAE Systems Developing Small Unmanned Underwater Vehicles to Hunt Enemy Submarines ,” USNI News , 18 July 2017.

Commander Allen is serving as executive officer for the USCGC Waesche (WMSL-751).

Mr. Allen is the  information security manager at Rubica, Inc., and a former sergeant in the U.S. Marine Corps.




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