Innovative strides in propulsion, navigation, and communication technology have led to a new breed of surface striking systems: explosive uncrewed surface vessels (E-USVs). Categorized as X-class boats—signifying a length of less than seven meters—these surface platforms are man-looped, remotely operated, single-use loitering munitions purpose-built to carry lethal payloads.1 E-USVs have become a vital asymmetric weapon for Ukraine, whose “Sea Baby” has proved remarkably effective against high-value ships and infrastructure.2 For example, on 5 August 2023, Ukraine used a nighttime Sea Baby attack to immobilize the Russian oiler Sig in the Kerch Strait. The drone’s pressure-triggered warhead ripped a 40-foot gash in the hull near her engine room, causing immense damage.
Marine littoral regiments (MLRs) will project power into the world’s littorals. As a stand-in force, an MLR is composed of small, mobile, and lethal littoral combat teams (LCTs) designed “to operate across the competition continuum within a contested area.” As “the leading edge of a maritime defense-in-depth,” they find, fix, target, and disrupt an adversary’s plans.3 E-USVs would be particularly suited to perform two primary LCT missions: expeditionary strike and antisurface warfare. The Marine Corps would be wise to field E-USVs as an immediate “fight tonight” capability.
Loitering munitions—a term commonly used to reference unmanned aerial vehicles (UAVs)—are low-cost, precision weapons that can be directed against static or mobile targets.4 “Kamikaze drones” fitted with warheads (as opposed to those that drop or launch explosives) detonate near or on their targets. Modern warships have built-in redundancies and damage-control capabilities to repel, defend against, withstand, and recover from many types of airborne attack. The risk of a loitering munition attack on a Navy ship is real, but the punch of a single kamikaze drone is relatively small, and defenses against UAVs are improving. (See “Make Every Marine a Drone Killer,” pp. 32–37, November 2023.)
Loitering surface munitions present a greater threat to ships because they can carry heavier payloads than similarly sized UAVs. Moreover, they are hard to detect in highly trafficked waterways and anchorages or during hours of darkness. Properly directed, they detonate at the waterline near propellers, magazines, or ballast-control systems, increasing the likelihood of shipboard flooding and catastrophic damage.5 E-USVs can be deployed discreetly from land, sea, and amphibious or subsurface platforms, far from the intended objective to limit risks to the operator. The U.S. Navy has explored offensive use of E-USVs as an alternative to UASs/UAVs, but until now the Navy’s systems have remained mainly experimental.
E-USVs’ water-jet propulsion systems, satellite communications, optical infrared lenses, and other sensors combine to make them multifaceted weapons capable of attacking both maritime vessels and infrastructure. In July 2023, a swarm of Sea Babies—using a tactic known as manned/unmanned systems teaming (MUM-T)—damaged the Kerch Bridge, a vital line of communication between Russia and Crimea. This example demonstrates how E-USVs can support naval objectives against a variety of targets through expeditionary strike, a key task for the sea-denial and offensive operations of the MLR.
Foreign navies are employing E-USVs even as the U.S. Navy’s investments in explosive uncrewed systems lag. While new formations such as Task Force 59 attempt to energize learning about sea drone employment, deliberate strategies to maximize the lethal effects of explosive variants are lacking. Even transforming existing technology such as the Navy’s ADARO USV into an explosive device would be a good first step.
E-USVs and Littoral Combat Teams
Littoral regiments and combat teams are expected to operate well inside an adversary’s weapons engagement zone in isolated expeditionary advanced bases (EABs). The confluence of operational and environmental challenges makes clear the need for low-signature mobile, sustainable, and versatile striking platforms that enhance command and control and produce intelligence.
Current precision fires systems such as the M142 High-Mobility Artillery Rocket System (HIMARS) and the Naval Strike Missile (NSM) are easily targetable once they unmask to fire. This necessitates a rapid “shoot and scoot” to survive. And they come with high costs in terms of dollars, production time, and complexity. E-USVs, on the other hand, are affordable, attritable, and replaceable.
The clandestine characteristics of X-class E-USVs would give an LCT a tactical edge across all warfighting functions while putting stress on the opponent’s decision-making calculus. Above all, E-USVs would be fires platforms, with added capacity for multisystem payloads that could collect and transmit information from sensors and optical instruments. Depending on configuration, each could feed the tactical common operational picture with live visual feedback and track data to provide input to the intelligence cycle. This would enhance the commander’s awareness and overall command and control.
An E-USV with a volume and footprint smaller than HIMARS or NSM launchers could be deployed remotely from a concealed holding area, reducing the risk of operator detection. Satellite communication between operators and E-USVs also would mitigate the possibility that a strike mission would result in the LCT being fixed and targeted, at least when the LCT’s location relative to the strike and the congestion and encryption of satellite signals were favorable.
E-USVs would furnish an LCT with additional combat power, enabling ample opportunities to surprise and overwhelm the enemy by varying distances and angles of approach, employing MUM-T swarm tactics, and combining surface and airborne fires in kinetic ambushes. Torpedoes, precision-guided bombs, and other conventional munitions create risk in the information domain because of potentially catastrophic collateral effects. However, a man-looped E-USV could reduce the potential for such negative outcomes.
Adversaries who seek protection in busy anchorages or congested waterways would not be safe when a remote E-USV operator can navigate around obstacles and bystanders; withhold detonation until securing a passable approach to the target; and deliver a focused, directional payload. Such strikes also could exact psychological and social gains against the enemy. For example, the Kremlin persistently diminishes the effects of Ukraine’s drone strikes in the media only to be contradicted when the Ukrainians release video feed from Sea Baby attacks that directly and conclusively undermine Russia’s credibility.
Given that the X-class subcategory of E-USVs is similar in size to the Polaris MRZR, they would be easy to embark and move around the battlespace. In principle, they would be compatible with the LCT’s Joint Light Tactical Vehicle and MRZR trailer configurations. Thus, a multitude of devices could be embarked, transported, staged, concealed, and employed for a given operation. Unlike NSM and HIMARS systems, which cost millions of dollars, E-USVs should be relatively simple to produce and made from abundant materials, with an estimated unit price of perhaps $250,000. E-USVs could be maintained at the operator level and would not strain the industrial base, bottle-neck the supply chain, or erode fiscal readiness.7
The Marine Corps has begun to recognize the value of USVs. In May 2023, it unveiled the Metal Shark Long-Range Unmanned Surface Vessel (LRUSV), an autonomous boat based on Metal Shark’s 40 Defiant patrol boat. With a range on the order of 1,000 kilometers, the LRUSV can launch UAVs and loitering munitions for intelligence, surveillance, and reconnaissance across vast regions. With $25.5 million allocated for future development, LRUSV production and innovation will benefit the Marine Corps for years to come but does not contribute to the present fight.
Overall, X-class E-USVs would greatly enhance the LCT’s immediate ability to operate across all warfighting functions. They are compatible with the LCT’s organic ability to transport, posture, sustain, and employ them in contested environments. Marine Corps Combat Development Command and Marine Corps Systems Command should begin the near-term investments that would enable rapid fielding and employment of E-USVs across the force.
1. Department of the Navy PEO-LMW, The Navy Unmanned Surface Vessel (USV) Master Plan (Washington, DC: Headquarters U.S. Navy, 2007).
2. H. I. Sutton, “Suspected Ukrainian Explosive Sea Drone Made from Recreational Watercraft Parts,” USNI News, 11 October 2022.
3. U.S. Marine Corps, A Concept for Stand-in Forces (Washington, DC: Headquarters U.S. Marine Corps, 2022).
4. Mark Voskuijl, “Performance Analysis and Design of Loitering Munitions: A Comprehensive Technical Survey of Recent Developments,” Defence Technology 18, no. 3 (March 2022): 325–43.
5. Scott Savitz, “The Age of Uncrewed Surface Vessels,” The Rand Blog, 15 November 2022.
6. Sutton, “Suspected Ukrainian Explosive Sea Drone.”