Last week, all 27 EU heads of state met in Brussels to oversee the continents largest military expansion in decadesa response to Cold War-level tensions. Yet, as Europe re-arms, a bigger threat looms: climate collapse, which no arsenal can deter. With unchecked climate change poised to halve global GDP in decades, security now hinges on rethinking energy itselfstarting with the military.Ministers wait for the start of an the EU Defence Summit in Brussels on March 6, 2025 in Brussels, ... [+] Belgium. European Council President Antonio Costa hosts a special EU summit dedicated to "European defence and Ukraine". (Photo by Thierry Monasse/Getty Images)Getty ImagesInsurance experts warn that unchecked climate change could slash global GDP by 50% in the coming decades, destabilizing economies and societies alike. Security isnt just about defense budgets and troop deployments; its about maintaining the economic foundations that nations rely on.As Europe re-arms, the critical question is this: Will it invest in a military that locks itself into fossil fuel dependenceor will it seize the opportunity to lead in green defense innovation, securing both its national security and economic future?"We cannot choose between either green or strong armed forces; we need strong and green at the same time."NATO Secretary General Jens Stoltenberg stands in front of a mine clearance tank on the grounds of ... [+] the military technology company FFG (Flensburger Fahrzeugbau Gesellschaft) in Flensburg, northern Germany, on June 20, 2023. (Photo by Axel Heimken / AFP) (Photo by AXEL HEIMKEN/AFP via Getty Images)AFP via Getty ImagesGreening the Armies A research paper from the Council of the European Union's General Secretariat, ... [+] exploring the possibilities of a sustainable and fossil-free military. As global defense sectors expand, this report examines how military innovation can align with climate goals to enhance security while reducing environmental impact.(c) European UnionThe Case for a Fossil-Free MilitaryMilitary Emissions: A Hidden WeaknessModern warfare is fueled by oil, and thats a problem.Global militaries account for up to 5.5% of total CO emissions, surpassing the emissions of entire nations like Japan or Russia.The U.S. Department of Defense alone emits more than Sweden or Portugal, making it the worlds largest institutional consumer of petroleum .Fuel transport missions in Iraq and Afghanistan exposed the high cost and vulnerability of oil-dependent supply chains. In 2007 alone, an estimated 170 servicemembers were killed or wounded safeguarding fuel convoyscasualties that starkly illustrate how these missions, relentlessly targeted by insurgents, became a lethal liability for American troops.European military leaders recognize this risk:If the military are the only ones using fossil fuels, then we will need to do our own exploration, our own refineries, our own logistics of the whole fuel chain, and that cannot be reality.We thought we had a deal with Gazprom, but we actually had a deal with Mr. Putin.A fossil-free military would significantly reduce these vulnerabilities, decreasing dependence on adversary-controlled energy sources and unstable fuel supply chains. While jet fuel and diesel remain essential due to their unmatched energy density, a clear, phased transition toward biofuels, hydrogen, and electrificationstarting with logistics and base operationscould meaningfully lower risks from geopolitical threats, volatile energy markets, and rising operational costs. Critics argue that fossil fuels energy density remains unmatched for combat, but phased transitionsstarting with bases and logisticsprove the shift is feasible without sacrificing readiness.The Biggest National Security Risk Is Not a Foreign AdversaryYet military emissions are only part of the challenge. The deeper issue is energy dependency itselfone that exposes supply chains to geopolitical shocks and battlefield vulnerabilities.For decades, military power has relied on oil-fueled logistics chains, diesel-powered armored vehicles, and jet fuel-reliant air forces. But as climate change accelerates, this dependence has become a direct national security risk.That risk isnt just tacticalits economic. As mentioned before, insurance experts warn that unchecked climate change could slash global GDP by 50% in the coming decadesdriven by crop failures, mass migration, and resource warstriggering economic and social destabilization on a scale never seen before.Geopolitical energy shocks also remain a significant threat. Russias invasion of Ukraine exposed Europes dangerous reliance on Russian fossil fuels, a vulnerability that directly extends to military energy supply chains.Meanwhile, China is rapidly positioning itself as a global leader in military clean energy innovation. From hydrogen-powered drones and AI-driven autonomous combat vehicles to nuclear-powered warships, China is integrating next-generation technology into its defense strategy. Perhaps most ambitiously, it is exploring space-based solar poweraiming to beam limitless, renewable energy from orbit to sustain military operations without reliance on fossil fuels. If Europe delays its transition, it risks not only an economic setback but also a strategic disadvantage in the energy-driven warfare of the future.Defense Spending Has Historically Driven InnovationRheinmetall taking part in EU project for sustainable forward operating basesImage credit: Rheinmetall Press Release"A significant improvement in energy ratios can also be achieved for military operations. Optimizing energy efficiency during deployed operations places special demands on technology. We look forward to using our skills and experience to support our customers' sustainability goals."Military R&D has transformed global industries before, and it can do so again:The Internet & GPS- Originally developed for military use, now essential for global commerce.Medical Advancements- Battlefield medicine has revolutionized civilian trauma care.Nuclear Power- First used in military submarines before becoming a global fossil-free energy source.A European commitment to green military technology would ensure both strategic dominance and cleantech leadership.Proven Examples of Fossil-Free Military techGripen has for the first time undergone a series of test flights with 100% biofuel. This ... [+] demonstrates that the aircraft can be flown with an alternative fuel and gives valuable knowledge for future possible use of alternative fuel.Photo: Saab Linus Svensson, Creative CommonsA whole array of recent examples prove that clean defense tech is not a pipe dream. Swedens JAS 39 Gripen fighter has successfully flown on 100% biofuel, demonstrating that high-performance military aircraft can transition to renewable energy. In France, the military has implemented Eco Camp 2025, deploying solar-powered field bases to reduce reliance on fuel convoys. Meanwhile, the British Army has developed hybrid-electric armored vehicles that lower fuel consumption and improve stealth, with future models potentially incorporating hydrogen propulsion to further reduce emissions.The war in UkraineThe war in Ukraine is demonstrating the strategic advantage of low-emissions weaponry. Ukrainian forces have successfully integrated low-cost, commercially available drones into frontline operations, reducing reliance on fuel-intensive military vehicles and aircraft. These drones offer enhanced battlefield agility, cost-effectiveness, and tactical flexibilitydelivering precision strikes and reconnaissance at a fraction of the cost and carbon footprint of traditional weapons systems. This shift not only improves operational efficiency but also underscores the future of warfare: adaptable, decentralized, and less dependent on fossil fuels.China taking the leadThe race for clean military technology is already underway. China has rapidly positioned itself as a leader in green defense innovation, integrating next-generation energy solutions into its military strategy. If Europe delays, it risks not only an economic setback but also missing a crucial opportunity to lead the future of defense. In 2024, Chinas investment in clean energy reached nearly the scale of global fossil fuel investments, totaling approximately $940 billion. More than half of this investment went into its electric vehicle, battery, and solar industries, significantly outpacing other global markets. Importantly, Beijing controls critical minerals like lithium, copper, and rare earth metals, securing a key advantage in the next generation of military and civilian energyIf Europe fails to transition to a fossil-free military, it risks not only being outmaneuvered in conflict but also becoming strategically dependent on foreign energy technologies.Conclusion: Fossil-Free Military Power: Europes Economic LifelineThe fundamental role of military power is not to wage war, but to prevent it. A well-equipped, energy-independent military serves as a deterrent, reducing the likelihood of conflict. But while a strong military can deter adversaries, it cannot deter climate collapse.If Europe integrates clean energy innovation into its military modernization, it will secure long-term energy independence, freeing itself from volatile oil markets and ensuring operational resilience. By leading the world in military cleantech, Europe has the opportunity to gain both strategic and economic dominance, setting the global standard for sustainable defense. At the same time, investing in fossil-free military technology will reduce global security risks, addressing climate-driven instability before it escalates into full-scale conflict.However, if Europe remains locked into another century of fossil fuel dependence, it risks being outpaced by China, which is rapidly advancing in military clean energy innovation. Operational costs will rise as fossil fuel prices fluctuate and supply chains become more fragile, making European forces increasingly vulnerable to energy shocks. Even its own deterrence capabilities could weaken, as outdated energy infrastructures fail to keep pace with the evolving demands of modern warfare.The choice is clear: Europe can lead the future of defense by embracing a fossil-free militaryor risk falling behind in the new era of security and power.When Militaries Fail to Invest in Green InnovationEurope is at a crossroads: it can embrace military clean techor double down on outdated systems. Unfortunately, recent defense procurements suggest that some nations are still stuck in the past.Despite the clear strategic and economic benefits of a fossil-free military, many defense procurements continue to lock in outdated technology. A striking example is Swedens recent 1.4 billion procurement of 775 military trucks. Instead of investing in modern, lower-emission alternatives, all vehicles were ordered with diesel engines based on the Euro III emissions standarda regulation that is 25 years old and has been replaced multiple times. These trucks will remain in service for decades, further entrenching fossil fuel dependency in Swedens military infrastructure. The reasoning? A perceived need for maintenance simplicity and avoiding reliance on modern emissions-control technologies like AdBlue. Yet while Sweden locks itself into fossil fuel dependence, other militaries are proving that hybrid and electric alternatives are already combat-ready and operationally effective.This failure to modernize is not just an environmental issueits a missed opportunity for strategic leadership. While China and other global powers invest heavily in green military technology, Europe risks falling behind by making procurement decisions based on outdated assumptions rather than future security needs.The question is no longer if militaries must decarbonizebut whether Europe will lead or be forced to followWith 800 billion in military investments planned, the EU faces a decisive moment: lock in fossil fuel dependence or shape the next generation of global security. To prioritize security, Europe must mandate green procurement in its defense budget, accelerate military-to-civilian tech transfers, and foster public-private cleantech partnershipssteps that overcome oil industry resistance to ensure energy independence and leadership. No military can defend against climate collapse, but innovation and investment can. The window is narrowingEuropes future depends on acting now.