Editor’s Note: This article is part of IWI’s Project Maritime, a series exploring the intersection of irregular warfare and the modern maritime dimension. The project aims to contextualize challenges and opportunities for irregular warfare in the maritime domain, including analysis of current events and emerging trends—from the Black Sea to the Panama Canal to the South China Sea to the Arctic. We are eager to share more details about the project in a formal launch later this month and invite your participation and engagement on this important topic.

We begin this series with an insightful contribution from Walker D. Mills, a member of the 2022–2023 IWI fellowship cohort. In addition to being a Marine Corps infantry officer, Walker is also a cohost of the highly regarded Sea Control podcast from the Center for International Maritime Security (CIMSEC). Walker offers valuable perspective on the often overlooked yet crucial role of riverine operations in modern irregular warfare and highlights its utility in the Ukraine conflict.

Special thanks to series editor Lisa Munde, the director of IWI’s Project Maritime and a veteran fellow at the Hoover Institution at Stanford University focused on maritime security and ocean governance.

The Dnipro River runs more than 1,300 miles, beginning near Smolensk in Russia and emptying into the Black Sea. It is the third-largest river in Europe and is nearly two miles across at its widest points. It cuts across Ukraine for over six hundred miles, from north to south, and bisects several of Ukraine’s largest cities, including the capital, Kyiv.

The Dnipro and its reservoirs power no less than six major hydroelectric stations that together comprise one of the “largest hydropower systems in the word.” It provided water for the reservoirs at the Zaporizhzhia nuclear power plant on the banks of the river and one of its tributaries, the Pripyat River, provided water for the cooling at Chernobyl. It is difficult to understate the importance of the river in Ukraine’s history, where it was a key part of the trade networks for luxury goods like walrus ivory and amber, linking the Baltic and Black Seas as far back as the Vikings and the ancient Greeks. The Dnipro River is a defining geopolitical and historical feature of Ukraine.

Given its centrality to Ukraine’s commercial and trade development, it is not surprising that the river has again become a focal point for the ongoing war in Ukraine. Both Russian and Ukrainian forces have used Ukrainian waterways as space to maneuver troops and move supplies. Ukrainian forces have become especially proficient in using small boats to carry out raids on Russian forces. Today, in certain areas, the Dnipro River is a de facto demarcation of the front line, and in other places is the de jure demarcation for regions claimed by Russia. The Russian withdrawal from Kherson and the west bank of the Dnipro leaves the river marking hundreds of miles of front line as the conflict passes into the winter.

In many places, rivers and adjacent infrastructure have become key terrain in the conflict. The New York Times reported that the battles in southern Ukraine have “revolved around rivers and bridges” since the opening days of the conflict. In May, a Russian unit attempting a river crossing on a pontoon bridge in eastern Ukraine took “significant” losses, an embarrassing setback for the Russian military. In October, Ukrainian forces surrounded as many as twenty-five thousand Russian troops in Kherson, where they were pushed up against the western bank of the Dnipro River and the crossing points could be targeted by artillery. More recently, Ukraine accused Russia of planning a “false flag” attack on the dam over the Dnipro at the Kakhovka Hydroelectric Power Plant, which would flood dozens of Ukrainian towns and villages downstream. A canal from the Dnipro in Kherson also provides some of the only freshwater supplies to Russian-occupied Crimea, making it a critical objective of the invasion. And in November, Ukrainian forces launched an amphibious assault on the Kinburn Peninsula in Crimea, which dominates the mouth of the Dnipro River, showing the interplay between riverine and coastal operations. In the Dnipro estuary, Ukrainian and Russian special operations forces are still struggling for control of key islands.

The importance of river systems in Ukraine highlights the disappointing reality that the United States is neglecting its own riverine capability and, by extension, its ability to control key terrain in future conflicts, even as the US government helps support Ukrainian riverine forces. Competency in riverine warfare will continue to be important in Ukraine whether the conflict continues with high intensity or dampens to a low boil because it can enable high-end combat operations, resistance, or local security operations. Despite clear lessons from Ukraine on the importance of riverine capability, the United States military does not have adequate forces that specialize in riverine or fluvial operations and security. In many military operations, rivers are seen only as obstacles to be crossed, despite the opportunities they present for maneuver and sustainment. However, properly trained and equipped units can use river systems to penetrate behind enemy lines and carry out targeted raids, sustain forces, or secure population centers. Riverine capability is especially important in irregular warfare and asymmetric conflicts because rivers are often key terrain for the military but also support critical infrastructure for civilian populations.

While the US military is equipped to conduct “wet gap” crossings and cross rivers (despite the Marine Corps’s divestment of its bridging companies), it is not adequately prepared to use rivers as a maneuver space—or prevent adversaries from doing the same—and it has not been for years. The US military should maintain a dedicated riverine capability in its conventional forces that can be employed in irregular warfare and beyond, and that can be exported to allies and partners in need. The Army and the Marine Corps have largely abandoned their own riverine capability, and the Navy has precious little left. The Navy’s special boat teams are capable, but only one of the three teams, Special Boat Team 22, is focused on riverine operations and operates a riverine-specific platform, the Special Operations Craft–Riverine (SOC-R). On the conventional side, the Navy’s Maritime Expeditionary Security Forces are chronically underresourced and focused on coastal rather than riverine environments. In a rare bit of good news for riverine capability, Marine Forces Reserve has been moving toward reestablishing a small craft capability for the Marine Corps, though it remains to be seen if the effort will be successful.

Ignoring Our History

Historically, the US military has assembled riverine units in an ad hoc manner when they were needed—usually for counterinsurgency operations. The US Navy, in particular, has a “long and varied but episodic history of riverine operations,” according to a Center for Naval Analyses report. The Army and Navy both have experience in riverine warfare dating back to the American Revolution and inherited experience from even earlier colonial conflicts along North American inland waterways. In the years before and after World War II, the US Navy had a dedicated “Yangtze Patrol” of riverine gunboats conducting security operations in China. Vietnam saw large numbers of soldiers and sailors working to provide security on the Mekong River and elsewhere in the country as part of the Mobile Riverine Force, which was inactivated in 1969. After the invasion of Iraq, Marines in a special riverine company were tasked with providing security for critical infrastructure along the Tigris and Euphrates Rivers, responsibilities that were later taken up by the Navy’s new (at the time) Coastal Riverine Force, which executed thousands of missions and helped train Iraqi police when the Marine unit was disbanded in order to free up personnel for other units. Around the same time an Army unit found the need for riverine capability so critical that it used local fishing boats to patrol Iraqi waterways. But today, there is almost nothing. The Navy has recently rebranded the Coastal Riverine Force as Maritime Expeditionary Security Forces because “riverine warfare is no longer an assigned mission area for the United States Navy, and the legacy name no longer captures the roles and missions of our force.” The change was also part of a shift from irregular warfare to great power competition.

Paradoxically, some of the best American riverine expertise is at the Naval Small Craft Instruction and Technical Training School (NAVSCIATTS), under United States Special Operations Command, but the school only instructs international students from allied and partner nations. NAVSCIATTS is a critical organization that helps the United States export riverine expertise to partners around the world where coastal and riverine forces are not only key to defense, but also to internal security and stability. The Pentagon recognizes that riverine expertise is important enough that we pay to bring hundreds of foreign students per year to the United States to learn it and related skills, but the US military doesn’t maintain adequate riverine capability itself. Worse, NAVSCIATTS is at risk of closure, a move that would also rob many US allies and partners of a key riverine training resource and further gut the US military of resident expertise in riverine operations.

Rivers Aren’t Going Away: The Joint Force Needs More Riverine Capability

The Pentagon needs dedicated riverine warfare capability focused on irregular warfare, but also valuable in other types of operations and in other contexts. Recent US wars have shown the enduring value of brown-water navies in irregular warfare in Iraq and Vietnam and Ukraine is continuing to demonstrate the value of riverine capability in high-intensity conflict. And exporting riverine expertise to allies and partners through training exercises with conventional US riverine forces and schools like NAVSCIATTS is valuable for all of the above.

Exporting US riverine expertise to allies and partners improves American relationships and interoperability. Colombia is one of the best examples of a country that has benefitted from US expertise in riverine warfare, and from US investments in Colombian equipment and training, to the level where Colombia is now a world leader in such operations. Rivers are critical in Colombia because the country relies on over 7,000 miles of navigable rivers for everything from transportation to border security and hydroelectric power. The Colombian military has sent dozens, if not hundreds, of sailors, soldiers, and marines to NAVSCIATTS as students, which has helped transform the Colombian Marine Corps into one of the most capable riverine warfare organizations in the world. Today, the Colombian Marine Corps boasts thirteen riverine battalions supported by indigenously designed and built riverine gunboats and naval aviation—units that were critical in beating back the FARC insurgency and forcing the group to the negotiating table in 2016. Much of Colombia is only accessible by river, and the Colombian Navy and Marine Corps are not just guarantors of security, but the only presence of the state in remote communities where they also help provide basic services like health care. Today, Colombia actually exports riverine expertise from its Centro Internacional de Excelencia Avanzada Fluvial (International Center of Advanced Riverine Excellence) to other countries from inside and outside the region, including Costa Rica, Ecuador, and Mozambique, and has designed a family of purpose-built riverine patrol vessels built by COTECMAR, a domestic shipbuilder.

Riverine environments present a dichotomy. On the one hand, recent research from Stanford University shows that navigable rivers historically played a large role in the foundations of economic and political development and are linked with prosperity and democracy. However, riverine environments are also more likely to suffer from insecurity than other environments as they “are susceptible to the greatest shock in security terms.” They are often adjacent to population centers and supply irrigation systems, drinking water, and power generation. Compounding the risk of insecurity, they are also vulnerable to severe weather events, including flooding and drought—both of which are projected to increase due to climate change.

From the Seminole Wars to Vietnam and Iraq, American riverine capability has been critical for irregular warfare and beyond, but assembling the brown-water navy has always been an ad hoc process. The ongoing conflict in Ukraine has demonstrated how important rivers and the riverine environment are to larger, more conventional conflicts in today’s era, characterized by strategic competition as well as irregular conflict. Recognizing this, the US government has announced multiple transfers of dozens of riverine patrol boats, including some likely from its own stocks—a move that ironically emphasizes both the importance of riverine capability and simultaneously, the US military’s disinterest in it. Unlike DoD’s donations of HIMARS, Javelins, and other weaponry, the patrol boats will not be replaced. The US military cannot again wait until riverine capability is in high demand before bringing it back; it needs to establish an enduring conventional riverine capability that can support irregular operations or a large-scale conventional conflict, and everything in between.

Walker D. Mills is a Marine Corps infantry officer and nonresident fellow at Marine Corps University’s Brute Krulak Center for Innovation and Future War and a nonresident fellow with the Irregular Warfare Initiative.

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

Image credit: Sgt. Colton K. Garrett, US Marine Corps