Energy is the lifeblood of our warfighting capabilities.

— Retired General David Petraeus

It was 1969, during Capt. Kern’s second tour of Vietnam. His fuel logistics hassles were even worse than those he faced his first time in the country when he was a cavalry platoon leader. During that tour, his soldiers had resorted to hanging bags of fuel from trees so that gravity would refuel their M113 armored personnel carriers. If they were in a good spot, they could drive the vehicles into a ditch and rest the fuel bags on the ground. Now Kern was responsible for not just M113s, but an assortment of forty vehicles including M551 Sheridan armored reconnaissance assault vehicles, a borrowed M548 cargo carrier, occasionally an M48 Patton tank, and M118 trailers. Diesel “recipes” were not standardized at the time and varied based on the season and the region. It took a while for the logisticians to get the local mix right. But the real hassle was the M48 and its gasoline. The gas evaporated so quickly in the hot climate and the engines ran so inefficiently that the beast required refueling twice a day. When soldiers unknowingly supplied a bladder full of jet aviation fuel for the affected vehicles it all had to be pumped out after the fact. Little did Kern know that when he arrived at Ft. Stewart years later as a battalion commander, he’d be dealing with an even greater variety of local diesel recipes, gasoline, and jet fuels for his vehicles.

To Gen. Kern and his generation of leaders, the “single fuel concept” (SFC) was a blessing. Historically, the SFC has provided increased interoperability and simplified logistics for the procurement, storage, and transportation of fuel, especially on the battlefield.

The shift toward a single fuel began in the late 1980s, aimed at streamlining the logistics headache of supplying a military that used half a dozen different types of fuel for aircraft and ground vehicles. Under this policy, which has since been further standardized with our NATO allies, the United States military predominantly uses JP-8 fuel to run its ground vehicles and land-based aircraft. JP-8 is commercial jet aviation fuel, with military additives for improved lubrication and inhibition of static, icing, and corrosion. The main advantage of using JP-8 as a common fuel is that unlike diesel and gasoline that can only be used in their respective engines, JP-8 can be used in both turbine-engine aircraft and diesel-powered ground equipment. While JP-8 is not perfectly suited for standard diesel engines, its chemical properties are close enough that the logistical efficiencies outweigh performance drawbacks.

To save costs, in 2012 all the services began switching to F-24 fuel in the United States, excluding Alaska. F-24 is similar to JP-8 but has greater commercial availability—although JP-8 has a lower freezing point, in part why Alaska was exempt from the switch. Overseas, however, the military continues to use JP-8, along with two other types, JP-5 and F-76. JP-5 and JP-8 are both jet fuels that are also used in ground vehicles. JP-5 is preferred for use aboard ships due to its higher flash point temperature. F-76 diesel fuel, which fires the diesel engines, gas turbines, and boilers aboard Navy ships, is formulated to remain stable and usable for years.

By the time Kern was a colonel and the 18th Airborne Corps was about to cross into Iraq during Operation Desert Storm, the SFC had solved the fuel diversity challenges he had faced in Vietnam. This time fuel posed a different problem: the sheer volume required. Before the attack on Jalibah Airfield by the 2nd Brigade, 24th Infantry Division, that he commanded, refueling was only just completed as vehicles were moving into their attack positions.

Single Fuel Dogma and the Supply-Demand Trap

As far as logistics go, the most salient single feature of the warfare in question was its dependence on the internal combustion engine both on land and in the air. For decades past, everybody had realized that dependence and some sought to reduce it. As of the present, though, instead of being diminished by new technologies it is still increasing.

— Martin van Creveld, Supplying War: Logistics from Wallenstein to Patton

While the SFC was originally meant to standardize the use of liquid fuels, this Cold War–era energy policy has become dogma that threatens the US military’s ability to adapt to future conflict and gain tactical and operational benefits. By restricting military users to a single fuel and thereby disincentivizing experimentation with alternatives, it has helped to create the mentality that petroleum fuels are the exclusive energy source in a forward environment. The Department of Defense needs to look past the single fuel concept and fully embrace the recommendations in its 2016 Operational Energy Strategy report to reduce the risks associated with the future operating environment through “innovation” and “diversification” of operational energy.

In 2018, DoD announced formally that alternative fuels were allowed for operational use. While well intentioned, this guidance will do more harm than good since it restricts the department to existing energy systems and processes. The policy limits alternative fuels to drop-in liquid petroleum replacements like synthetic fuels—it does not allow for true alternatives like hydrogen or propane fuels. It requires that alternatives be “compatible with existing equipment and infrastructure” and that producers must “provide significant volumes to support an expeditionary, globally deployed force.”

Despite extensive experimentation with alternative fuels at leading federal research labs, SFC dogma is stifling transition into the force at the scale needed to realize tactical and operational benefits. Even though all services have expressed interest and are investing in alternative energy research, the single fuel concept is the most significant barrier to their adoption. Beyond a pervasive bias against incorporating new energy sources into existing energy logistics, any potential implementation of a new fuel suffers from the chicken-and-egg problem where logisticians won’t invest in supplying new fuels to platforms that don’t exist and acquisitions officers are reluctant to procure new platforms that rely on fuel infrastructure that doesn’t yet exist at scale. Without the demand from alternative fuel–powered tactical platforms, there is little incentive for logisticians to create the necessary logistics infrastructure and trained personnel to increase supply. Meanwhile, program managers are not interested in setting requirements for new tactical vehicles that run on a fuel for which there is no supply chain. Both logisticians and program managers accustomed to a single-fuel environment seem unwilling to accept the initial risk of breaking through this supply-demand trap to fund large-scale programs that use new fuels and electric powertrains.

What started as a way to streamline the logistics for US armored units in Europe now threatens to constrain operational energy innovation at a critical time for the US military. The US military is relying on innovative new operating concepts like Multi-Domain Operations and Expeditionary Advanced Base Operations (EABO) to counter aggression by China and Russia, but the concepts for operational energy are stuck in the Cold War. Distributed operations, seen as a critical piece to all of the services’ emerging operating concepts, will strain logistics networks in new ways, especially with regard to fuel and operational energy.

Leaders inside and outside the Pentagon, however, fear that the US military will be unable to operationalize new warfighting concepts because outdated logistics will be the limiting factor. Marine leaders have become increasingly preoccupied with the challenge of distributed and contested logistics in the Pacific. Wargaming in the service has shown that sustainment, particularly fuel sustainment, is a leading operational constraint. The commandant did not mince words with his assessment in 2020:

I am not confident that we have identified the additional structure required to provide the tactical maneuver and logistical sustainment needed to execute DMO [Distributed Maritime Operations], LOCE [Littoral Operations in a contested Environment] and EABO in contested littoral environments against our pacing threat.

While the House Armed Services Committee’s Future of Defense Task Force report identified emerging operational concepts as one of the primary ways the Pentagon can provide the US military with a “decisive advantage” in future conflicts, it cautioned that “they are not yet fully viable.” The 2016 Department of Defense Operational Energy Strategy warned that “these logistically intensive future concepts may not be supportable.” Even adversaries have messaged the US military that maritime logistics will be contested. A RAND Corporation report found that both China and Russia could launch an “interdiction campaign” in a conflict to restrict the flow of battlefield necessities, including fuel, to US forces, further complicating logistics.

The Promise of Alternatives

Despite multiple attempts to de-escalate, the United States was forced to engage militarily in 2030 to protect its allies in the western Pacific. Capt. Smith had been recently assigned to the Marine Littoral Regiment in III Marine Expeditionary Force. His experimental infantry company was tasked with establishing an expeditionary advanced base. One platoon ran a hydrogen forward arming and refueling point (H-FARP) system that could rapidly refuel their array of hydrogen-powered platforms: Stalker and Blackjack UAVs, Reckless utility terrain vehicles (UTVs), and stratellites—small stratospheric balloons that temporarily provide satellite-like capabilities. The long-endurance hydrogen-powered UAV allowed Capt. Smith’s company to maintain persistent UAV coverage around the clock, scanning the adjacent seas for enemy ships. Without the three-times-longer flight endurance enabled by the hydrogen power train, this mission would have been impossible. Another platoon hitched a radar and antiship missile launcher to hydrogen-powered UTVs and drove along the coastline, scanning the skies for enemy aircraft and, if necessary, providing fires. Thanks to the vehicle’s hydrogen fuel cells, which ran efficiently even when idling, these Marines were able to keep their radar and communications gear powered without emitting any detectable thermal or audible signature. When the adversary jammed GPS and communications, Smith’s platoons quickly reestablished secure comms and navigation with the launch of two hydrogen-fueled stratellites that they could deploy themselves at 0.002 percent of the cost of a new satellite and would loiter for days. Meanwhile adjacent units not equipped with alternate sources of energy struggled after enemy missile strikes destroyed their prepositioned fuel stores and adversary submarines and land-based missiles prevented the Navy and Maritime Sealift Command from bringing in bulk fuel.

DoD has been studying, prototyping, and experimenting with several alternatives to petroleum for decades but these have not been deployed in quantity. This essay focuses on the most promising energy sources for tactical power. Other alternatives like solar, wind, and geothermal have been integrated into installations infrastructure but their low efficiency makes them poor options for use during operations.

Ammonia: A liquid when compressed, ammonia is produced from hydrogen and nitrogen. Even though it is caustic and hazardous in concentrated form, it sees wide industrial use. In the 1960s the Army developed the “Energy Depot Concept,” which would have used a small nuclear reactor to produce hydrogen and nitrogen as feedstock for ammonia. Commercial shipping companies in Japan and Europe are working to use ammonia as the fuel for cargo ships to eliminate carbon emissions.

Synthetic Fuels, Alcohol Fuels, and Biofuels: All US Air Force aircraft have now been certified to fly using a 50 percent synthetic fuel blend made though the Fischer-Tropsch process, of which ten million gallons are expected to be produced daily by 2030. More than 98 percent of the gasoline sold in the United States contains ethanol, the most common biofuel, to increase octane and reduce emissions. Ethanol and other alcohol fuels can also be fed through fuel cells without needing oxygen, which makes them leading candidates for use in unmanned undersea vessels. In 2013 the secretary of the Navy announced that “the Great Green Fleet will signal to the world America’s continued naval supremacy, unleashed from the tether of foreign oil” by operating on 50 percent biofuel and implementing fuel efficiency measures. The Navy demonstrated the effectiveness of this approach in 2015 when the USS Makin Island was able to stay at sea over a month longer than it previously had by using biofuels.

Mobile Nuclear Power: By packaging reactors into a standard shipping container and designing them to avoid catastrophic meltdowns despite physical damage, nuclear power has the potential to address DoD’s tactical power needs. In late 2020 the Energy and Defense Departments issued contracts for prototype small, modular, and mobile nuclear reactors. Companies such as HolosGen and X-energy are currently developing and marketing miniature, mobile nuclear energy platforms for commercial and government use. Nuclear fuel innovations such as tri-structural isotropic particle fuel promise more robust and inherently safer reactor operation, by encapsulating small particles of nuclear fuel in individual safety packages. However, independent reports have criticized the idea as being too expensive and too risky.

Hydrogen: Hydrogen holds significant potential for DoD, since it can be produced within theater, both regionally and locally from numerous energy sources. Traditional production techniques use coal, natural gas, or burned waste. Electrolyzers, which consume electric power and water, are the leading method for producing zero-emissions “green” hydrogen. US allies across the globe are making significant investments in hydrogen, with the Japanese building a “hydrogen society,” the French investing €7 billion to build 6.5 gigawatts of electrolyzer capacity, the Germans exploring the possibility of using gas pipelines to carry 100 percent hydrogen rather than Russian natural gas, and the Australians aiming to become a “hydrogen powerhouse.” Multiple organizations are developing novel ways to produce hydrogen from recycled aluminum.

The military has been building prototypes to demonstrate the benefits of hydrogen power for nearly two decades. The Naval Research Lab and Army Ground Vehicle Systems Center have successfully developed several hydrogen-fueled platforms, including record-shattering UAVs. Vendors for both the US Army and European militaries are developing packable fuel cells to charge soldiers’ lithium-ion batteries. DoD has successfully produced synthetic petroleum fuel from hydrogen and carbon dioxide extracted from seawater, and could produce synthetic petroleum from the exhaust of diesel generators at home or abroad.

Enable our Future Commanders

During his military career, Gen. Kern, his soldiers, and the logisticians who supported them benefited from the standardization and simplified logistics offered by the single fuel concept. In the intervening forty years, the commercial sector has revolutionized power and energy technologies. Commercially available products that use nonpetroleum fuels provide capabilities that internal combustion engines simply cannot. Nonpetroleum fuels also hold the potential for regional and local production, which would finally sever, or at least shorten, what retired General James Mattis once described as DoD’s “tether of fuel.”

It is time to update the single fuel concept to encourage the adoption of platforms powered by nonpetroleum fuels and build the required logistical infrastructure. Just as fuel policy enabled Gen. Kern and his generation to win during Operation Desert Storm, a modernized fuel policy will enable future military leaders, such as the younger officers on the byline, to win our nation’s future conflicts.

General (ret) Paul Kern has thirty-eight years of service in the US Army including time as commanding general of the Army Materiel Command, commander of the 4th Infantry Division, and commander of 2nd Brigade, 24th Infantry Division during the 1991 Persian Gulf War.

Captain Walker Mills is a Marine infantry officer currently serving as an instructor at the Colombian Naval Academy in Cartagena, Colombia. He is also the Military Fellow with Young Professionals in Foreign Policy and a fellow at the Brute Krulak Center for Innovation and Future War.

Captain Matthew Santoli is a Marine artillery officer and a recent graduate of the Harvard Kennedy School’s Master in Public Policy (MPP) program.

First Lieutenant Benjamin Flanagan is an Air Force pilot trainee and a recent graduate of the Harvard Kennedy School’s MPP program.

Erik Limpaecher leads the Energy Systems Group at MIT Lincoln Laboratory in Lexington, Massachusetts. He is a non-resident fellow of the Marine Corps University’s Krulak Center and a member of the Defense Science Board task force on Defense Department Dependence on Critical Infrastructure.

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

Image credit: Sgt. Gregory T. Summers, US Army