On the evening of April 13, 2022, two Neptune antiship missiles streaked out from the northern coastline of the Black Sea to fatally strike the Russian cruiser Moskva. The flagship of Russia’s Black Sea Fleet sustained heavy damage and sank the next day as it attempted to return to Sevastopol in Crimea, becoming the largest warship to be sunk in wartime since World War II. This event, which represented a cross-domain solution to an asymmetric disadvantage, immediately transformed the maritime complexion of the Russo-Ukraine War. While anecdotal, the Ukrainian military’s successful attack demonstrated how ground forces equipped with long-range strike systems have unrealized potential to impact, and potentially transform, fundamental aspects of joint warfare.

This episode suggests that warfare may be evolving in ways that are empowering ground forces to more decisively influence tactics and strategy in maritime environments. For the US Army, in particular, it means that modernization of an older idea called the fortress fleet concept could allow novel contributions to joint and coalition seapower. Defined by naval strategist James R. Holmes as an approach where ground forces employ “long-range precision-guided weaponry” to “clear adversaries from a massive offshore zone,” the concept, echoing the Ukrainian army’s attack on the Russian navy, employs an array of artillery, missiles, drones, electronic warfare, and amphibious assault measures across both mobile platforms and hardened facilities to deny adversary access while enabling power projection.

Once disdained by naval theorists such as Alfred Thayer Mahan for limiting naval freedom of action and distracting from massive fleet battles, the dramatic expansion of long-range strike by land-based batteries with advanced detection and targeting mechanisms invites reconsideration of a fortress fleet strategy. This more robust approach to maritime affairs would allow the Army, as mandated in its capstone doctrine, to better “support joint defeat of enemy integrated air defenses, fires and strike complexes, surveillance, and reconnaissance, and integrated C2 networks to enable success.” It would enable, if optimized for the coastal mission, the landpower institution to protect maritime decisive points and forward basing while ultimately facilitating survivable naval offensive maneuvers at a larger scope and scale.

Fortress Fleet Concept

Coastal fortresses have long been an important component of naval warfare by providing fortified positions to protect military access and national interests in contested maritime spaces. With the long-standing British bastion at Gibraltar, the robust Russian defenses at Kaliningrad, and the sprawling harbor complex at Manila Bay in the Philippines representing notable historical examples, the construction of strategically located coastal forts bristling with cannon represented an important, and highly technical, field of expertise for the artillery and engineering branches of nation-state armies. In many ways, these imposing coastal fortresses came to serve as symbols of dynastic and national power for both domestic and foreign audiences while creating obstacles for adversary designs.

However, given the relatively short ranges of cannon and rocket artillery in the seventeenth, eighteenth, and nineteenth centuries, as well as the expense of constructing and manning large fort complexes, some theorists cautioned against over investing in fortress-centric naval strategies. Criticized by Mahan as a “radically erroneous” idea, the preeminent naval strategist of his time argued that such an approach would lead to a defensive mentality that could only limit the offensive spirit of a battle fleet and result in dispersal of warships along extended coastlines. This criticism, which he illustrated with a biting critique of the Imperial Russian Navy in the Russo-Japanese War, sought to minimize the role of coastal fortifications in favor of decisive fleet engagements, merchant marine harassment, and the eventual strangulation of an economic blockade.

This assessment, and the context of joint warfare in maritime settings, changed dramatically with the advent of both carrier and ground-based aviation in World War II. While coastal artillery remained mostly limited in range to line-of-sight targeting from fixed points, maneuvering fleets and forward island airfields assumed outsized importance in both the Japanese centrifugal offensive of 1941–1942 as well as the subsequent American campaign to liberate the archipelagos of the Western Pacific. Called “unsinkable carriers” due to their depth, resiliency, and durability, forward airfields, in particular, allowed Army Air Forces fighter, bomber, and surveillance aircraft to exercise unprecedented operational reach with an intensity and endurance that naval aviation could not hope to match.

Enabling Joint Seapower

Fast forward to the twenty-first century, and a new generation of ground-based detection and strike technologies are threatening to transform the very character of maritime warfare. With the dramatic sinking of the Moskva serving as a harbinger of future trends, the Army has an emergent opportunity to reimagine the fortress fleet concept by building out fortified positions at locations that hold critical value to American and coalition interests. Seeking to neither replace nor displace the traditional roles of the US Navy and US Marine Corps, America’s primary landpower institution could rather invest in twenty-first-century coastal fort complexes in forward areas that mitigate vulnerabilities and amplify strengths in order to enable joint protection and maneuver in increasingly lethal maritime environments.

This evolved approach centers on the age-old role of coastal forts in both antiaccess and protection operations, which continues to be a primary responsibility for Army forces in littoral settings. With dramatically increased missile ranges, a panoply of drone innovations (aerial, surface, and subsurface), and advances in active defense systems currently redefining relationships between fire and maneuver, ground forces can employ a variety of traditional and new targeting arrays to both safeguard forward ports for naval resupply and deny adversary interdiction in troubled regions such as the South China Sea, the Baltic Sea, and the Persian Gulf. These cross-domain fires, when integrated with physical fortifications, electronic countermeasures, combined arms ground assault, and expanded logistical capacity, offer more effective options to safeguard power projection in support of US joint efforts.

A revitalized fortress fleet concept leverages the Army’s potential to enable decisive naval maneuver within range of adversary systems. With the centerpiece of the US battlefleet, the vaunted aircraft carrier, now under threat from an emerging array of antiship missiles and further threatened by the ominous onset of hypersonic missiles and advances in drone technologies, land-based batteries have a unique potential to employ superior magazine depth, higher volume of fire, and densities of drone swarms. Increased Army contributions would provide expanded endurance to absorb and recover from strikes in order to provide, as required by Army multidomain operations doctrine, “windows of opportunity” for potentially vulnerable warships to aggressively move into contested seascapes and deliver devastating strike packages.

Taking this idea further, a joint fortress fleet concept could also enable the US Marine Corps to better execute its new expeditionary advanced base operations concept with a lighter and more agile force design. With the Army providing an assured forward base of operations, expanded volumes of fire and counter-fire, and critical aspects of maritime air defense, deployed Marine forces could enjoy greater access and survivability for amphibious assaults that may be challenged by adversary precision fires. Similar to the opportunities that could be afforded to the Navy, the Army’s unmatched capacities for fires, logistics, electronic warfare, hardened construction, and, perhaps most important, formation reconstitution, would open fleeting vectors for Marine air-ground teams to execute amphibious maneuver and seize key terrain.

This evolved approach, as a joint concept, would essentially comprise a hammer-and-anvil solution to the acute maritime access threat posed by peer competitors such as China and Russia while securing forward positions prior to the commencement of armed conflict. With the fortress fleet providing the baseline to assure protected access and defendable positions in competitive spaces, the traditional maritime services would benefit from emergent opportunities to attack, or at least threaten, fatal points of enemy vulnerability. This approach, seeking to evolve rather than reinvent joint seapower, could increase US military capability to inflict attritional exhaustion over time or catalyze systemic collapse with decisive assault in noncontiguous maritime settings.

Fortress Fleet Strategy

The famed British admiral Horatio Nelson once reportedly quipped, “a ship’s a fool to fight a fort”—a reference to the conditional advantages that nineteenth-century coastal batteries held over their warship counterparts due to superior elevation, larger gun calibers, deeper magazine depth, and capacity to repair battle damage. While the rise of attack aviation upended that notion in the twentieth century, the sudden onset of long-range detection and missile strike has created new dynamics that may empower the once-derided fortress fleet concept. While general fleet actions such as the epic Battle of Midway in 1942 seem improbable given the US Navy’s blue-water primacy, more complicated engagements in proximity to littoral or archipelago landscapes are much more likely to occur, with unpredictable results.

This is because, similar to the dizzying transformation of airpower during World War I, a new generation of precision reconnaissance-strike technologies are changing how militaries conceptualize lethality and survivability. With the recent Nagorno-Karabakh and Russo-Ukraine Wars already demonstrating how missiles, drones, and ubiquitous surveillance have challenged ground offensives, the fate of the Moskva portends similarly disruptive results for naval and amphibious maneuver across contested seascapes. In future maritime combat, this will likely become only more complicated as land forces project a panoply of technologies that include next-generation interceptors, autonomous systems, synchronized drone swarms, artificially intelligent targeting, and new arrays of cyber and space capabilities from behind fortified bastions.

Moving beyond the technical and the tactical, the evolved fortress fleet would likewise have concrete strategic effect on national and coalition interests. Representing an extension and evolution of the fleet-in-being concept, where the very existence of premier naval power affects adversary calculus, the development of twenty-first-century coastal forts would assure allies of American political resolve and signal coalition reliability in expeditionary theaters. Similarly, and equally valuable, the long-term military investment in forward areas would deter adversaries by constructing reciprocal antiaccess architectures that not only dramatically raise the cost of territorial aggrandizement, but also counter malign informational designs by presenting visible and credible intent to defend national interests.

Looking toward an uncertain future, and echoing the success of the Ukrainian army in thwarting the Russian navy in the Black Sea theater, the fortress fleet concept can redefine the interplay of landpower, airpower, and seapower in maritime conflict. Seeking to fulfill the US military’s mandate to, as described in the 2022 US National Security Strategy, employ “integrated deterrence” to “shape adversary perceptions of risks and costs of action against core U.S. interests,” a revolutionized commitment by the Army to deny enemy access, safeguard national interests, and enable naval position and maneuver in competitive maritime environments promises to enhance, and potentially even transform, the projection of joint seapower. This reimagined contribution, representing just the next iteration in the ever-changing character of warfare, may provide a critical, and even vital, military capability for the American republic to compete and win in the twenty-first century.

Lieutenant Colonel Nathan Jennings, PhD, is an associate professor and Army strategist at the US Army Command and General Staff College.

The views expressed are those of the authors and do not reflect the official position of the United States Military Academy, Department of the Army or Department of Defense.

Image credit: Maj. Robert Fellingham, US Army