We are not yet at a paradigm-shifting moment in the role of autonomous or robotic systems at sea. Nor are we likely to reach a revolutionary precipice within the period in which the U.S. Navy must begin making the transition to a truly hybrid fleet — that is, the integration of autonomous platforms designed to operate as part of an ocean-going battle force. This means the Navy’s approach to acquiring and fielding unmanned systems for deployment at sea should ultimately reinforce and support the maritime domain’s still-dominant weapons system: long-range anti-ship missiles.

We have learned a lot about the use of unmanned systems in Ukraine and the Red Sea. Yet we risk misapplying lessons from these often land-based conflicts if we do not consider the unique nature of war from the sea, where longer ranges, maneuvering targets, and weapons systems (ships and aircraft) are inherently limited in what they can carry to the fight. Naval analysts should interpret lessons on unmanned systems employment within the unique constraints of operating from the maritime domain. We can do that by looking at the intersection of cost, plenty, survivability, and reconstitution. In Ukraine and Yemen, a reliance on plentiful and cheap systems, a dearth of sophisticated weapons, relatively close quarters, and largely interior (or illicit) lines of communication all encourage combatants to prioritize the regeneration of cheap drones over weapons system survivability as the simplest pathway to combat resilience. Simply put, it is easier to acquire thousands of replacement racing drones or dozens of loitering munitions than to invest in higher-cost, more complex, less risk-worthy platforms and weapons.

Not so from the sea. There, platforms (and thus, their survivability) are much more important because of the attritional nature of missile warfare. These platforms will remain central for as long as the U.S. Navy operates large, crewed ships, which are not going away anytime soon. Naval vessels bring inherent constraints that fundamentally shape how the hybrid fleet will make use of robotic systems. Ships, crewed or not, are constrained by size, weight, and power — and operate far from logistics nodes. Moreover, rearming them can mean taking offensive power off the front lines. Such factors do not mean unmanned systems have no value at sea. But they do shape how those systems should be employed on the ocean in ways that are distinct from what we have seen in other conflicts to date.

The Maritime Fight Has Not Transformed

In the maritime domain, despite initial impressions from Ukraine and the Red Sea, unmanned systems are still best understood as operating in the context of an attrition-based form of missile warfare. A close reading of meaningful operational effects at sea in both cases in fact shows the centrality of long-range precision naval fires in two ways. First, traditional missiles continue to hit the hardest, creating the most impactful losses and effects. Second, as we will see below, where robotic systems have been strategically effective, it is often in tactical or operational conjunction with a missile.

Unmanned surface vessels have certainly garnered well-deserved attention through their use by the Ukrainian military. These systems have been so valuable to a ship-less Ukrainian navy that the country created a new brigade dedicated to their operations. Yet at core, cruise missiles remain elemental to the Ukrainian naval effort. After two years of war, about half of the major Russian platforms that Ukraine had destroyed were lost to long-range land-attack cruise missiles targeting vessels in port. Anti-ship cruise missiles also scored successes, not least the newsworthy sinking of the cruiser Moskva. Based on data from the open source project Oryx we assessed in spring 2024, of large Russian platforms destroyed beyond economical repair (cruisers, submarines, landing ships, and minesweepers), five of eight were the result of missile strikes. Unmanned systems had been most destructive for the smallest craft (and against fixed infrastructure).

Where unmanned surface vessels have had greatest effect, it is as part of a more complex system of capabilities that reserves a prominent place for long-range fires. Marine Corps University professor Benjamin Jensen writes that what really matters is how Ukrainian unmanned surface vehicles are “combined with raids, cruise missile strikes, intelligence, deception, and electronic warfare that keep the Russians constantly guessing and wondering what will hit them next.” Indeed, it was Ukraine’s cruise missile attacks that created the tactical dilemma for Russian forces operating in the northwest portion of the Black Sea. This forced Russia to consolidate its remaining ships, as at Novorossiysk, only then exposing them to surface drone attacks and land-attack cruise missiles shot at stationary vessels in port.

A related story comes via Ukraine’s only major amphibious operation, retaking Snake Island. In that campaign, Turkish-made TB2 drones contributed to destroying Russian fast attack boats. Yet the relatively permissive environment these drones were operating within was derivative of the successful cruise missile strike on Russia’s major local air defense resource (the Moskva). The latent threat that unmanned aerial vehicles posed to near-shore vessels lacking air defenses materialized only when higher-end munitions pushed the Russian battle force out to sea, leaving small craft operating within the reach of drones. We have seen few such successes further out to sea.

Data from the Red Sea again reinforce the assessment of the underlying prominence of missiles in maritime conflict. An open source compellation of incidents assembled by Lloyd’s List suggests that the Houthis are finding much more operational success with missiles (cruise and ballistic), even as drones catch headlines and soak up defensive interceptors. Of the 20 known or suspected vessel strikes in the first (roughly) six months of Houthi aggression, four came from unidentified projectiles, two were attributed to drones, and 14 were attributed to missiles. The most damaging attacks, and the only attack to result in loss of life, all appeared to be missile strikes.

The Question of Cheap Mass

Centering the missile in war at sea helps us better understand where unmanned systems fit in the future hybrid fleet that the Navy is in the process of defining. Planners will somehow have to add more missiles to the equation, make existing missiles more effective, add additional resilience to the kill web (how missiles get to targets), or better conceal and defend crewed platforms from missile attacks. But there is one more key factor, that of cheap mass in war from the sea. This hinges on understanding naval survivability, or the fundamental nature of attrition in naval warfare.

Attrition reigns at sea because magazine constraints dictate combat potential in the maritime domain in ways that are not neatly comparable to war on land, where defense is more operationally feasible. Limitations on a ship’s total missile inventory, coupled with a platform’s exposure to detection and its distance from the resupply of friendly shores, produce a different mass-versus-precision calculus for navies than for land forces. Massed fires are clearly central to how the U.S. Navy intends to execute its Distributed Maritime Operations concept. But mass as a standalone value at sea is constrained by how much platforms can carry and their ability to survive and reconstitute combat power in the battlespace. Cost, plenty, survivability, and reconstitution offer a useful framework for thinking about how manned-unmanned conflict at sea is distinct from some of its applications on land.

Survivability and reconstitution often go hand in hand. To survive as a force is to make for more rapid regeneration and reattack. In Ukraine and Yemen, the wide scale use of low-cost systems has somewhat modified that calculus for land-based forces. As Stacie Pettyjohn observes, “drones do not have to be survivable if they are cheap and plentiful because one can have resiliency through reconstitution.” The iterative innovation in Ukraine and Yemen, then, is that these systems are abundant, expendable, and thus shift the calculus in the balance of survivability and reconstitution.

Resiliency through mass reconstitution of cheap systems is an attractive concept and one that naval analysts have an interest in pursuing. In the present moment, however, this concept is also much less obviously operative at sea given the platforms the U.S. Navy will fight with for decades to come. That is in part because “cheap” and “plentiful” mean something different for the U.S. Navy than for Ukraine, Russia, or the Houthis. This implies different kinds of unmanned systems — and different theories of employment — than those seen in Ukraine or the Red Sea.

Drones are already undoubtedly cheaper than many of the weapons systems they complement, as well as the weapons systems often used to defeat them. They may even stay cheaper, in some contexts, though that is far from a certainty. U.S. defense programs tend to send costs skyward, but not all this price hiking is simply a result of gold-plating requirements. The kinds of systems that the U.S. Navy would need to employ against an adversary like the Chinese navy demand more sophistication and hardening than those used in Ukrainian, Russian, or Houthi brute force approaches. This could include high data-rate satellite communications equipped with anti-jamming capabilities, target discrimination capabilities, and autonomous guidance and decision-making in terminal approach.

By contrast, Ukrainian, Houthi, and Russian high-density, low-cost, limited-sophistication theories of victory depend on the value of mass in war on (or from) land, where there are comparatively short supply lines and engagement ranges. This reliance on cheap electronics also means that the balance of power has equalized quickly. As Pettyjohn explains: “because most of the drones in Ukraine are commercially derived systems, the technology has quickly diffused to the enemy and has not provided an enduring advantage to either side.” Rapid iteration of cheap tech has lowered the floor or barrier to entry, but not necessarily raised the ceiling of strategic effect in either conflict.

Moreover, cheaper does not mean cheap, and we should not expect the cost predictions for systems common in a land war where both sides have internal lines of communication to hold true for the Navy’s needs at sea — doubly so as adversaries gain more expertise in countering those systems. Much of the commentary on drones downplays the expected costs imposed by future efforts to defeat them, which strikes at the very premise that they are enduringly cheap and effective.

Navies have significant constraints that are very different from combatants firing from interior lines. For decades to come, the bulk of the U.S. Navy’s force will remain crewed platforms, and there is no reconstitution without platform survival for a force like this. Consequently, versatility is king at sea. The limited launch cell space on a ship and the unpredictability of the nature of an inbound threat argue in favor of maximizing the density of the most capable interceptors onboard a vessel (many of which double as offensive missiles for the same reason). The result is a high bill and ship-imposed constraints on munitions density, which is what has fed the news cycle on the cost imbalance between a U.S. Navy missile like the SM-2 taking down cheap Houthi aerial drones. In other words, this imbalance is not simply a product of overly expensive U.S. missiles against “innovative” Houthi drones. A review of America’s own missile inventory shows that interceptors are typically about twice the price of offensive missiles because of defense’s technical demands. Precision in defensive interceptors, and the requirement to “bat a thousand” when it comes to ship self-defense, make those missiles necessarily expensive. Until we achieve breakthroughs in directed energy or other non-kinetic defeat options, missile defense will continue to be a more expensive proposition than anti-ship offense, even setting aside the underlying value of defending a $2 billion warship and its crew.

Ultimately, in a war at sea, platform survivability and munition reconstitution (how a ship gets rearmed and put back on station) are the most operationally important criteria for massing effects against the enemy. For this reason, the Navy’s requirements for small autonomous systems that take up precious space on its crewed or autonomous vessels will prioritize versatility: capable of helping the ship fend off complex multi-axis attacks and contributing to offensive multi-axis attacks, all while limited in the total number fieldable from a single platform. That basic insight underscores how the simple idea of forgoing the purchase of some multi-million-dollar missiles to buy a few hundred or thousand cheap drones to put at sea is not even math for a destroyer that may face anything from a Houthi drone to a Chinese hypersonic missile when it leaves port. The ship’s need to assure survivability is the first law of reconstituting naval combat power and will remain so for as long as the U.S. battle fleet anchors on large, crewed, missile-shooting platforms. We should be transparent in acknowledging that the path to the hybrid fleet flows through those constraints.

Conclusion

We are in an evolutionary phase of unmanned integration, and this fact should inform the Navy’s transition to the eventual hybrid fleet. This era requires naval concepts of employment for unmanned systems that center the missile, with robotic platforms serving important but ultimately additive roles and missions. Looking through this lens, we already see the notable but caged utility of unmanned systems play out in both Ukraine’s naval battle and the Red Sea. Where unmanned systems have been strategic in creating effects in the maritime balance of power, it is often in coordination or convergence with the cruise missile. It is the partnership with cruise missiles that sets the table for unmanned system successes. It is the missile that remains the unheralded but decisive naval munition, as evidenced by these real-world operations.

In contrast with war on or from land, at sea the challenges of rearming a ship, the longer tactical distances, the larger necessary warheads, and the limitations on available size, weight, and power all create crosscutting constraints that shape drone use. The technical requirements for naval operations threaten to change the alchemy of cost and plenty that analysts find so appealing about drone use onshore. This finding obligates naval analysts to better conceptualize the value of drones in what may be the long calm preceding the coming of the swarm, that hypothesized paradigm shift that may one day supplant missiles in naval warfare. In their current iteration, however, robotic systems are an important development but so far fundamentally additive for a Navy that remains dependent on the dominant weapons system of its domain. The hybrid fleet should emerge from that central thesis: the missile still matters.

Dr. Joshua Tallis is a senior research scientist at the Center for Naval Analyses and the author of The War for Muddy Waters. From 2021–2023 he was the center’s advisor to the U.S. Sixth Fleet commander. The views expressed here are his own.

Image: Stuart Phillips