The Second World War was one of movement, and the drive to secure oil fields shaped campaigns and dictated war strategies. The Soviet occupation of Bessarabia, northern Bukovina, and the annexation of the Baltics in 1940 brought the Soviet forces closer to the Romanian oil fields that Germany depended on, thus serving as one motivation for the decision to launch Operation Barbarossa in June 1941. Later, in November 1942, with disaster looming for Field Marshal Friedrich von Paulus’ Sixth Army, which was then surrounded in Stalingrad, Adolf Hitler remained fixated on the oil fields of the South Caucasus. In his orders to Field Marshal Erich von Manstein, who was eventually tasked with trying to break the Soviet siege of the German troops hunkered down in ‘the kessel’, Hitler declared, ‘unless we get the Baku oil, the war is lost’.

Oil similarly played a crucial role in imperial Japan’s decision to go to war in 1941, alongside anxieties about other vital raw materials and resources. The future of the empire’s oil supply had been badly endangered by its deteriorating political relations with the United States, the United Kingdom, and the Dutch East Indies. The Allies were, at the same time, attempting to secure the passage of oil from the United States across the Atlantic, given the imminent threat of German submarines. The Allied success in breaking the Enigma codes used to deliver messages to Germany’s submarines is now seen as a significant turning point in the Battle of the Atlantic, and the war as a whole. Securing the Atlantic allowed the United States to supply far greater quantities of oil to US and Allied forces, fuelling operations across the European theatre.

Across the world in the 1940s, the key to fighting a modern war of movement was oil, alongside other key energy resources and raw materials. This, in turn, drove competition over access to vital resources – and the key locations where they were produced. Without control of these resources, waging warfare in the modern way was impossible.

In the modern world, reducing fuel dependence is similarly a crucial aspect of warfare. At a time of heightened geopolitical tensions, in an age of renewed great-power rivalry, competition for resources is fuelling a new, mercantilist race for energy and raw materials. In this era, as before, fuel assets are a measure of state capacity and military power. The Russo-Ukrainian War demonstrates the devastating impact of fuel shortages. Indeed, Russia quickly weaponised fuel dependence when it invaded Ukraine, halting all liquid-fuel supplies, which accounted for about two-thirds of Ukraine’s domestically consumed energy. The message is clear: smaller countries without a stable, dependable access to energy resources risk being unplugged, weakened, and falling prey to stronger powers.

However, this could be rapidly changing. Many innovations in warfare have taken place on the frontlines and battlefields of the Russo-Ukrainian War; energy could be the next frontier, with profound implications for the global energy order and geopolitics. New innovations, such as hydrogen fuel, could fundamentally transform the nature of conflict – and revolutionise the possibilities of military strategy. Unlike fossil fuels, hydrogen can be produced directly at the edge of the battlefield. This opens up the possibility of remote and renewable generation in multiple locations, including military bases, thereby enhancing resilience and fundamentally changing the planning of energy availability. In all conflicts since the Second World War, access to specific resource-rich locations has been essential to unlocking the resources needed to wage a war of motion. Yet if new hydrogen fuels could be adopted on a large scale, it would mean that military strategy no longer revolves around oil fields located in specific places to the same extent as before. A war of movement would no longer be dependent on control of specific geographical points.

Recent instances of warfare innovation suggest that progress in this regard could be quite rapid. As technology has been evolving, new developments are changing the way in which wars are fought. The conflict in Ukraine has already opened up what is deemed to be a new era of drone warfare. In this same context, a further step in the direction of fuel innovation may be within reach, and may have transformative consequences. For example, this could take the shape of using a solar-powered electrolyser to produce hydrogen fuel cells, which can power road, air and maritime transport. Apart from its ultra-portability, which decreases logistical constraints, hydrogen comes with other advantages, too. Its high energy density enables a drone to fly three times further than batteries do. This endurance thus makes hydrogen fuel cells more suitable for longer missions. In addition, the lower thermal and acoustic signatures of hydrogen make it better suited for military stealth operations compared to traditional diesel, which is noisier. All these advantages are also paired with a smaller environmental footprint, given hydrogen’s clean production process.

Hydrogen is already seen by NATO, alongside advanced batteries, as a potential enabler of key military capabilities. The idea is to turn the West’s great comparative advantages in scientific innovation into enhanced battlefield performance. Through its 2022 Strategic Concept, NATO has also committed to leverage green technologies and invest in the transition to clean energy sources. Tests with hydrogen fuel cells, such as one carried out recently in France, highlight the efficiency, reliability and practical benefits in field operations. Moreover, the United Kingdom’s first hydrogen-powered drone flight has recently been completed successfully. That represents an important advancement in long-range aerial capabilities. All these aspects promise to unlock greater energy resilience for NATO countries.

Nonetheless, there are still challenges to the large-scale deployment of hydrogen fuel cells. These relate to its production and infrastructure development. Storage poses logistical issues, as hydrogen is a light gas and has a low volumetric energy density, so that it must be compressed at high temperatures, liquefied at very low temperatures, or stored in solid form using advanced materials. This complexity highlights the need for further studies to guide the selection of the optimal storage solution, since hydrogen is still not readily available on the battlefield. These challenges also suggest that, as the state of the technology currently stands, the price of hydrogen fuel for military use would be prohibitive. Some estimate that fuel cells are five to ten times more expensive than systems driven by the internal combustion engine.

The logistical and price issues that present obstacles to the wider use of hydrogen fuel could also be overcome through increased investments. As hydrogen helps with energy independence and resilience, its synergies with the defence industry are already becoming increasingly apparent. The recent commitment by NATO Allies to annually invest five per cent of GDP in defence by 2035 could serve as an accelerator of the hydrogen technological process, through developing infrastructure, or further supporting the research and development of better storage solutions.

We are at a crossroads, which may mark a departure from the past wars of movement that had oil as a key determinant of military strategy. If successful, cultivating hydrogen could enhance NATO powers’ strategic autonomy, especially through tackling the fuel dependence challenge, while also providing an environmentally sustainable solution. Clean, locally produced hydrogen for military operations would address past issues of fuel dependence alongside current issues related to conventional fossil fuels. All in all, it could represent a revolution in warfare and military operations as profound as any witnessed over the previous five centuries.