Reimagine the Role of Amphibious Forces in Campaigning

As communist threats loomed over Europe in 1947, President Harry Truman announced a policy to “support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures.”¹ The policy would become known as the Truman Doctrine, and support included U.S. forces who would advise, assist, and facilitate the flow of arms and equipment to troops in countries such as Turkey and Greece.

U.S. diplomat George F. Kennan saw a need for U.S. naval forces in the eastern Mediterranean to deter Soviet aggression. Ready forces at sea would support regional allies and partners as needed.² The Chief of Naval Operations ordered just such a naval force to the Mediterranean, and in January 1948, a battalion landing team from the 2nd Marine Division also deployed to the region.³ This expeditionary maritime force assured allies and partners through exercises and rehearsals and by persistently deploying credible capabilities.

That naval force eventually became the U.S. Sixth Fleet, and the reinforced Marine battalion became the prototype for today’s Marine expeditionary units (MEUs). This Navy–Marine Corps team deterred threats throughout the Cold War and continues its mission to this day. It would come to include an amphibious ready group (ARG) of ships purpose-built to maximize Marine Corps capabilities.

ARG/MEUs still deter threats. But as the tools of deterrence evolve, so must their wielders. Long-range, precision antiship, antiair, and antiarmor fires are increasingly becoming autonomous and unmanned.⁴ Admiral Samuel Paparo, Commander, U.S. Indo-Pacific Command, recently described such systems as hallmarks of his deterrent efforts—able to turn the Taiwan Strait into a “hellscape” for any aggressor.⁵ These capabilities require guaranteed access for and support from key enablers. Deterrence across the range of conflict will require a wide variety of advanced capabilities persistently deployed to support allies and partners on key terrain.

A modernized ARG/MEU team, prepared to conduct amphibious defense with stand-in forces (SIF) ashore, could fulfill these vital roles and ensure deterrence in the modern battlespace.

Moving On from the Past

Today’s ARG/MEU teams are not task-organized, networked, or equipped to confront the greatest threats now facing the United States. For two decades, they have been structured to operate in volatile regions that are not crucial to U.S. interests.⁶ From 2003 until 2023, every ARG/MEU deployed from the United States to the U.S. Central Command area of responsibility to serve as a crisis-response and limited-contingency force.⁷ Task organizations have focused on reprising those known roles instead of supporting deterrence in Europe and the Indo-Pacific.

In those critical regions, antiaccess/area-denial technologies challenge the current ARG/MEU employment concept in high-end conflict. ARG/MEUs must be able to reach an area of crisis, but amphibious operations of the kind developed in World War II and still codified in doctrine are ill-suited against modern adversaries’ abilities to sense and strike targets in the maritime domain.

Concepts such as SIF, expeditionary advanced base operations (EABO), and amphibious defense adapt the Marine Corps to fight more effectively in the conditions expected of future high-end conflicts.⁸ Capabilities such as air and maritime sensors, long-range fires, and uncrewed and autonomous platforms support these concepts. Collectively, these concepts and capabilities better assure allies and partners and deter conflict.

SIF assist ARG/MEUs by increasing sensing and protection, accessing key terrain, and enabling the introduction of critical capabilities embarked at sea. SIF are crucial to the Marine Corps’ continued expeditionary relevance. The MEU and SIF complement each other through the phases of competition, crisis, and conflict.

Competition: Building Advantages

During competition, both the ARG/MEU and the SIF work to develop advantages that will persist through crisis and into conflict. These advantages derive from relationships built on trust with allies and partners. The MEU and SIF demonstrate national resolve in complementary ways. Stand-in forces, by living within range of potential adversaries’ weapons, signal U.S. commitment to allies and partners, while the MEU signals U.S. intent to rapidly respond with them during a crisis. The MEU and SIF, operating in concert, provide enduring advantages that will be important during a crisis or conflict.

One of the greatest examples of cooperation among SIF, ARGs, MEUs, and allies is occurring on the flanks of Taiwan. The recently established 12th Marine Littoral Regiment (MLR) and Japan’s recently reorganized 7th Surface-to-Ship Missile Regiment constitute a stand-in force that persistently senses and is capable of striking threats in the maritime domain.⁹ Japan’s Amphibious Rapid Deployment Brigade, the U.S. 31st MEU, the Japan Maritime Self-Defense Force’s Mine Warfare Force, and U.S. Seventh Fleet’s Expeditionary Strike Group 7 all work to bolster the defenses of Japan’s Southwest Islands.¹⁰

To the south, the Philippine Marine Corps’ recently established Coastal Defense Regiment (CDR) and Marine Amphibious Ready Units (MARUs) are key components of the service’s archipelagic coastal defense concept.¹¹ The persistent partnership between 3d MLR and the Philippine CDR improves these nascent organizations and entrenches them in the terrain they may have to defend.¹² Similarly, recent engagements during Exercise Balikatan between Philippine MARUs and elements of the 15th MEU and Boxer ARG demonstrate how forces at sea may maneuver to positions of advantage and reinforce SIF.¹³ Persistently postured stand-in forces and rapidly emplaced MEUs enhance the capabilities of allied counterparts and find them greater room to engage on key terrain.¹⁴

In addition, ARG/MEU teams are highly interoperable with the allied expeditionary forces that are most likely to respond in a crisis. The Australian Amphibious Force, the United Kingdom’s Littoral Response Groups, and France’s fleet of Mistral-class landing ships with embarked Marines increasingly field modernized capabilities; they habitually operate with ARG/MEUs. Through cooperation and integration in major exercises such as Baltic Operations and Talisman Sabre, ARG/MEU teams have become the linchpin for incorporating highly capable allied expeditionary forces.¹⁵

Crisis: Deploying and Using Capabilities

In a crisis, SIF and MEUs present distinct and complementary advantages. Stand-in forces can preposition and operate regularly alongside allies and partners to gain cultural literacy and operational context. While the SIF will have to take actions to prepare for conflict, their forward presence gives them incredible speed relative to the rest of the joint force.

The ARG/MEU provides amphibious mobility and embarks versatile capabilities. While the United States benefits from the ability to preposition matériel across the world, the placement of critical capabilities is limited on key terrain such as the Southwest Islands of Japan, or Palawan and Northern Luzon in the Philippines. As SIF enhance the capabilities of allies and partners on such terrain, ARG/MEUs facilitate the rapid emplacement of additional capabilities and forces during a crisis. This affects an adversary’s calculus and better positions allied forces for mutual defense.

During a crisis, the MEU and SIF can exploit the advantages accumulated in competition. Unit-level partnerships between stand-in and expeditionary forces on Taiwan’s flanks deter conflict. In league with allies and partners, they provide mutual support for a potential amphibious defense. This enduring campaign builds the interoperability necessary to deter conflict and respond capably if an adversary initiates hostilities.

Conflict: Overcoming Limitations

What ARG/MEUs need now is a modernized concept of employment and the tools that support it. Existing and emerging capabilities could better arm contemporary ARG/MEUs to command and control, sense, and strike in conjunction with SIF. ARG/MEU teams today could carry Naval Strike Missiles on Navy/Marine Corps expeditionary ship interdiction systems and Standard Missiles in containerized expeditionary launchers.¹⁶ Maritime Strike Tomahawk missiles and Precision Strike Missiles with seekers capable of maritime targeting also could enhance the ARG/MEU’s range and lethality.¹⁷

Similarly, ARGs could host existing autonomous and uncrewed capabilities organic to the Navy’s new Unmanned Surface Vessel Squadrons 1 and 3.¹⁸ MEUs could augment ARGs’ unmanned surface capabilities with HERO-120 loitering munitions on board long-range unmanned surface vessels currently being prototyped by the Marine Corps.¹⁹ ARG/MEUs could store and maintain these assets at sea. By employing these sensing and strike capabilities at decisive times and places, they could overcome the limitations prepositioning agreements and political sensitivities present during competition and crisis.

ARG/MEUs must work in concert with SIF—but they also must be ready to fight as stand-in forces themselves. At the outset of a potential conflict, ARG/MEUs could emplace anywhere from 10 to 30 expeditionary advanced bases (EABs) on key maritime terrain within 96 hours via organic amphibious connectors and assault support aircraft. Air and ground sensors from the MEU could increase the resilience of kill webs by observing and tracking targets using Link 16, and this expeditionary sensing capability could be significantly enhanced by including Ground/Air Task-Oriented Radars.²⁰ SIF and allied and partnered forces could support these EABs with fires and logistics, even in contested environments. Simultaneously, an ARG could deploy hundreds of containerized M18 unmanned surface vessels, each with a 1,000-pound payload, to support the amphibious defense, then maneuver to mitigate the effects of adversary weapons in fewer than four days.²¹

With SIF limiting their physical and electromagnetic footprint to increase survivability, this complex choreography could be orchestrated by the ARG/MEU’s robust command-and-control (C2) capabilities. As a forward, integrated Navy–Marine Corps team under the operational control of a fleet commander, the ARG/MEU could command and control the seaward portion of an amphibious defense that incorporates allies, partners, SIF, and the wider joint force. The ARG’s landing force operations center and supporting arms coordination center are mobile, forward C2 nodes that could extend fleet maritime operation centers (MOCs). When augmented by MEU battle staff certified in rapid-response planning, these nodes could coordinate operations in the littorals, prosecute fires, and dynamically target threats in conjunction with the fleet MOC. The ARG/MEU team could also coordinate undersea warfare in support of an amphibious defense.

The MEU could replicate similar capabilities ashore and extend a common operational picture to SIF, allowing them to provide data to allies and partners. The MEU also could enhance SIF with robust ground-mobile C2 capability equipped with Joint All-Domain Command and Control and Common Aviation Command and Control systems, as well as a capacity to link into combined and joint fires networks. This framework may enable the ARG/MEU to direct the seaward and landward portions of an amphibious defense.

Extending this C2 apparatus across the littorals would protect friendly surface vessels and optimize fleet maneuvers. By closely coordinating the SIF’s sensors, fires, and effects with the ARG/MEU, fleets can exploit temporary cognitive and physical gaps in an adversary’s dynamic targeting process. Such synchronization also would facilitate the delivery of fleet fires and effects in support of stand-in forces.

Putting New Concepts into Practice

The SIF and ARG/MEU are a combined-arms team that creates advantages across the phases of competition, crisis, and conflict. SIF thrive in competition, building their awareness of the operational environment, while providing multidomain C2 as well as maritime fires in conflict. They create opportunities to better employ the ARG/MEU in competition and increase its survivability in conflict. The SIF is best situated to coordinate the multidomain maneuver necessary for the MEU to penetrate within the range of adversary weapons, while also facilitating coordination with allies and partners.

With Russia waging war against Ukraine, the specter of wider conflict looming over Europe, and a growing threat in the Indo-Pacific, ARG/MEUs must forge a stronger bond with SIF across the globe. These forces must become more complementary, and the ARG/MEU must modernize its embarked sensing and strike capabilities to better deter and defeat contemporary threats. ARGs must embark and train to employ unmanned and autonomous systems, while MEUs must be modernized with capabilities to fight as SIF.

With long-range fires, unmanned vessels, and air and maritime sensors, the ARG/MEUs of tomorrow could bring the force necessary to rapidly establish an amphibious defense in depth, with mutually supporting fires across domains. Together, this combined expeditionary force of ARGs, MEUs, SIF, allies, and partners could deter a conflict, or rapidly gain an advantage if hostilities commence.²²

From their inception, MEUs were designed to deter threats and reassure allies and partners through a focused yet flexible force. These Marines at sea served as a vital component of deterrence before and must be modernized with the right concepts and equipment to do so again.