This article is taken from the July 2026 issue of The Critic. To get the full magazine why not subscribe? Find our subscription offers here.
There is once again a significant movement for disarmament in Britain. Previous generations of activists were motivated by a view of the arms industry as both wasteful and a source of pernicious destruction. What they were arguing for was what they aimed to achieve.
Today’s movement is different. The most influential disarmers in British public life do not say they want disarmament and do not realise that they do. They advocate it by another name.
That name is “greening the military”. Since armed forces are major carbon emitters, the argument runs, net zero commitments means they must be overhauled — at pace.
Who makes this case? Well-placed, often senior figures in and around the armed forces. The Ministry of Defence has published its “Climate change and sustainability strategic approach”, aiming at net-zero emissions by 2050. The British Army now pledges to cut its fuel consumption through the electrification of its operational vehicle fleet. This is its big “bet”. The idea has worked its way into NATO doctrine, too. The former secretary general, Jens Stoltenberg, declared that the forces of the North Atlantic can be both “green and strong”. Can they?
In Britain, the spearhead of this strategy is Lieutenant General Richard Nugee, now the non-executive director for climate change and Net Zero at the Ministry of Defence. “The military,” he insists, must “reduce its greenhouse gas emissions as far as possible towards net zero.” How far is possible? “There is an important caveat: we must not compromise our capability or effectiveness as a defence force, as the requirement to defend the nation must remain our purpose.”
That caveat is important. The people advancing this agenda are not pacifists, and they do not sound like radicals. They stress, on the one hand, the supreme emergency of the climate crisis; on the other, they direct the military only towards what is “possible” by way of net zero, and they attach reassuring caveats about maintaining — and improving — military strength. They promise that we can be green, and quickly, and still be strong, all at once.
This optimism is fuelled by a belief that dual-use technologies such as hybrid-electric vehicles and sustainable aviation fuel can “reduce emissions whilst boosting military performance”. Brigadier Matthew Cansdale, Head of the MoD’s Future Force Development, insists that “electrification is a win-win for the Army as it enables operational advantage, reduces logistic demand, and puts the Army on the path to meeting net zero 2050 sustainability objectives”.
A win-win. Not only is the moral argument said to be compelling; a green revolution is said to promise enhanced military power as well. This is the heart of the matter.
Let us grant the true part first. Reducing a force’s appetite for fuel is not merely a concession to the climate. It can be sound warfighting. The logistic tail — the convoys of fuel and water that sustain a deployed force — is a battlefield liability, and a deadly one. In Iraq and Afghanistan, resupply convoys were amongst the most dangerous places a soldier could be. A lighter, less thirsty force is a more survivable and more agile one. Here, green and strong really do point in the same direction.
But notice where: at the margins, in the supporting systems, along the supply tail. It collapses the moment the argument closes in on the carbon-intensive core — the platforms that actually deliver combat power. Here, “green and strong” is unrealistic.
Consider “Green Defence: the defence and military implications of climate change for Europe”, the detailed 2022 report of the International Institute for Strategic Studies, a study broadly sympathetic to the greening project. Even this friendly audit makes it clear that a transition to clean energy will be expensive, technologically demanding and corrosive of core capabilities.
Amongst the “challenges” the IISS identifies: “heavy armoured, combat support vehicles, fast jets, bombers and transporters” will be “unable to be driven by all alternative propulsion in the near future”. The “large-scale use of biofuel” remains a “challenge” for maritime platforms, given the volumes required and the production cost. Sustainable aviation fuel is “relatively inaccessible and expensive”, and may underperform fossil fuels. Nuclear propulsion is powerful but carries “high operating costs” and demands investment in infrastructure and disposal.
Then there is the problem that “a scalable battery-driven aircraft for fast jet, bomber or transport operations is not possible in the near term”. For lighter logistic vehicles the prospects are better — yet even there, batteries remain “heavy, slow to charge and offer limited range”, and electrified fleets would need charging stations of “likely greater than ten megawatts”. Such stations would themselves become targets to defend, stretching forces further. The IISS cites the German Ministry of Defence, which judges that propulsion based on batteries or fuel cells alone cannot meet the requirements of armoured fleets.
The evidence tells us that, at the core, the enabling technology does not yet exist and certainly not affordably at scale. In turn, meeting net zero targets will mean fielding fewer major warfighting capabilities.
Consider what a target year of 2050 actually means for an institution that builds on the timescales defence does. A tank, a submarine or aircraft entering service today will still be fighting in the 2060s and beyond. Major platforms are conceived, procured and fielded across horizons of 30 to 50 years.
A net-zero target for mid-century therefore does not grant us a comfortable quarter-century to tinker at the edges. It means the major design decisions taken from now on must already assume the alternative-propulsion technology that does not yet exist for armour, fast jets and maritime platforms. That is not a patient strategy. It is a wager that breakthroughs will arrive on schedule, placed against the next generation of warfighting capability.
The careful caveats do not remove the scale of that risk. And the trade-off cannot be ducked, only managed. Resources spent on one thing exact costs elsewhere. Money, materials and time spent greening vehicles and bases, or developing alternative fuels, will mean fewer vehicles and fewer well-fortified bases. Even pursuing the hoped-for breakthroughs is resource-intensive: money spent unlocking new power sources is money not spent making existing instruments more accurate, better armoured or more lethal.
A military greened at accelerated pace necessarily becomes, in the interim, a weaker one. There is an inescapable tension between the drive to cut emissions on a defence timescale and the capacity to fight and sustain major warfighting at scale.
That tension becomes especially acute over artillery. Ukraine holds against Russia today through the daily, mass use of artillery fire — an arm of war that emits on firing, and again across its manufacture and transport. “Green munitions” may be possible around the edges, in the reduced use of hazardous chemicals. But there is only so far one can lighten the footprint of long-range projectiles that use explosive chemical reactions to create craters. Either you field non-green artillery, or you do not field artillery. Claiming to support Ukraine’s self-defence whilst demanding accelerated defence greening is like saying you like apples but oppose the orchard. Note that Poland, facing Russia’s imperial storm, seeks exemptions from strict EU decarbonisation rules. Warsaw grasps the trade-off, even if others don’t.
So: around the edges, in the supporting systems, greening is achievable, and sometimes beneficial. But as the issue closes in on the core — tanks, fighter-bombers, submarines, heavy artillery — it becomes prohibitively costly and difficult. These capabilities are already carbon- and capital-intensive, resting on a robust defence-industrial base. The transaction costs of overhauling that base would be high, as would the long-term damage to capability.
Climate change, the greeners say, is a threat to military capability. This is true, but it is a slow-burn risk measured in decades
To this, the greeners offer a serious reply. Climate change, they argue, is itself a threat to military capability: flooded bases, heat degrading readiness, resource conflict, instability in a melting Arctic. This is true, and worth weighing. But it is a slow-burn risk measured in decades, and it is a global phenomenon that British force structure cannot appreciably alter. A weakened conventional deterrent, by contrast, is a near-term and decisive vulnerability that an adversary can exploit this decade, not in the next century. The two risks are not on the same clock, and confusing their tempos is part of how the trade-off comes to be denied.
These problems are compounded by a harsh feature of international life. If we weaken our militaries for the sake of net zero, we cannot be confident that others, least of all our adversaries, will follow. They may be reluctant to surrender capability and make themselves vulnerable, precisely when security fears are sharpest. They may say they are greening their forces — just as states sign emissions agreements and then defect through creative accounting.
The deeper problem is one of verification: no state will accept intrusive monitoring of its military decarbonisation, because surveillance creates vulnerability. This is the classic arms-control predicament. China’s professed climate commitments, advanced even as it builds coal-fired power stations, are merely the most visible instance of a general rule.
It will be said that such reasoning is merely the free rider’s excuse: that everyone pleads the other party’s inaction, and so no one acts. But this is not the free rider’s plea. The free rider withholds a contribution that would otherwise secure the prize. Here there is no prize to secure. Britain’s total emissions are under one per cent of the world’s. It could return to the Bronze Age tomorrow and scarcely move the global figure, and the major emitters are not playing.
To bear heavy costs for a benefit that will not materialise is not virtue. The point is not fatalism but proportion: a duty to sacrifice presupposes that the sacrifice buys something, and for a one-per-cent emitter weakening its own defences, it does not.
Much defence net-zero advocacy, in its eagerness to meet a planetary emergency, says far too little about the gamble it proposes. Here is the true “bet” on the table: that for the sake of lowering emissions, we should make ourselves more vulnerable to other armed states, some major powers, some of them predatory. In our time the stakes are higher still, for Britain’s senior security provider, the United States, has by turns threatened an ally in Denmark, coveted its territory in Greenland and warned it might abandon NATO altogether.
None of this requires inaction. If Britain is to pursue a low-carbon force as an urgent matter, it will look very different from a policy that treats the climate crisis as a relative priority rather than an absolute one. There is a respectable case for the latter: a gradual, partial, phased programme to reduce emissions and improve sustainability — and to strengthen our capacity to withstand climate effects — without undermining the country’s defences. The opposite of an unachievable, self-threatening utopianism is not paralysis. It is confronting the cost.
But the predicament is real, and it will not be wished away. The “green military” question is a subset of the “green Britain” question, and it carries the same hard logic: doing harm to things most people genuinely care about — self-defence, and the defence of our neighbourhood — in exchange for a contribution that is, on its own, marginal. The tone of this advocacy is measured; the bet it places is not. The lambs may vote for veganism. The wolves look on, unmoved.
