We are told yet again that the British Government spends too little on defence. The Americans want more money. NATO wants more money. The Ministry of Defence wants more money. Everyone except the taxpayers wants more money for weapons. The immediate dispute concerns a gap between what the armed forces claim they need and what the Treasury is willing to provide. John Healey resigned as Defence Secretary after concluding that the proposed settlement was inadequate. His successor, Dan Jarvis, arrived at the recent NATO meeting in Brussels without a completed defence investment plan. Meanwhile, the American Defence Secretary, Pete Hegseth, has announced a review of the American military presence in Europe and hinted that countries failing to spend enough may find American support reduced. That explain the pressure campaign. Spend more. Rearm faster. Prepare for danger.

The assumption behind this campaign is that Britain’s military weakness is self-evidently undesirable. This assumption deserves examination. Weakness is a relative term. A country may be weak for one purpose while remaining strong for another. The question is not whether Britain can still project power overseas on the scale expected thirty years ago. It is whether this ability is necessary. To answer that question, we need to examine what British armed forces have actually been doing since the end of the Cold War.

For most of the twentieth century, the official justification for military expenditure was defence against invasion. Soviet armies stood in Central Europe. The possibility of a major war, however remote, was real. After 1991, this justification largely disappeared. No comparable threat emerged. Yet military spending continued. More remarkably, military interventions accelerated. Iraq, Afghanistan, Libya, Syria and numerous smaller operations followed in succession. Britain had fewer direct threats than at any point since the eighteenth century. Simultaneously, it became involved in more foreign wars than at any point since the nineteenth.

The purpose of Western armed forces changed. They ceased to function primarily as instruments of national greatness and became instruments of international management. The old empires had mostly vanished by the 1960s. Their functions did not vanish. These were transferred to a system of alliances, treaties, international institutions, military bases, sanctions regimes and occasional interventions. The language changed from imperial duty to humanitarian responsibility. The reality was much the same. Armed force was used to maintain an international order beneficial to those who governed it.

Britain’s governing class ceased long ago to think in national terms. Since 1945, and especially since the end of the Cold War, British foreign policy has become increasingly subordinate to the priorities of a wider Atlantic system. Successive governments have differed on domestic questions. They have shown unthinking agreement on foreign policy. Iraq, Kosovo, Afghanistan, Libya and Ukraine were all presented as moral obligations. What they had in common was that none involved the defence of Britain. British soldiers and British weapons were sent abroad because the governing class regarded itself as part of an international managerial elite whose responsibilities extended far beyond these islands. Whether these interventions served British interests was scarcely considered. The interests of Britain and the interests of the Atlantic system were assumed to be identical.

For three decades after the collapse of the Soviet Union, the Western powers enjoyed an almost unprecedented freedom of action. Russia was weak. China was still emerging. The world economy appeared increasingly integrated. Financial interests flourished. Manufacturing could be transferred overseas without obvious consequences. Military interventions could be launched against countries unable to resist effectively. This was the age of globalisation, and it encouraged the illusion that military power could be projected indefinitely at modest cost.

That illusion is dying. The American aggression against Iran illustrates the point. The most expensive military machine ever assembled found itself checked by defensive systems costing a fraction of what was supposed to brush them aside. The same pattern appears elsewhere. Israel possesses overwhelming technological superiority over every force that opposes it. Yet its recent campaigns have exposed the limitations of expensive military power when faced with determined resistance. The Israelis have turned to mass-murder of civilians not only because that is what they enjoy and do rather well, but because that increasingly is all they can do. The Russians have learned similar lessons in Ukraine. Equipment costing millions can be destroyed by drones costing thousands. Vast concentrations of resources are increasingly vulnerable to dispersed and inexpensive forms of defence.

For centuries, military advantage tended to favour the richer side. Wealth bought ships, artillery, fortifications and armies. The relationship between expenditure and power was imperfect but broadly reliable. Today, that relationship is becoming less predictable. Cheap drones, precision-guided weapons and decentralised command systems increasingly threaten expensive and concentrated systems. This does not make attack impossible, but it does make attack less likely to succeed.

Military power ultimately rests on productive capacity. Ships, aircraft, missiles, munitions and electronics must be made somewhere by someone. Countries that manufacture little cannot sustain prolonged military competition. Countries governed primarily for the benefit of financial interests tend eventually to discover this fact. The same people who spent decades insisting that manufacturing no longer mattered now wonder why Britain struggles to expand weapons production.

This contradiction lies at the heart of the current NATO dispute. The Americans want Europe to spend more because American priorities are changing. The strategic assumptions of the post-Cold War era are collapsing. The United States increasingly expects European countries to carry a greater share of their own defence burden. This is rational from an American perspective. The question is whether Britain should respond by attempting to recreate military capabilities designed for an age that is passing away.

I do not think it should. Britain is an island. Geography remains relevant despite the fantasies of global strategists. No hostile army can cross our land frontier because we have none. Any serious threat must arrive by sea or air. The first duty of defence policy is therefore command of our surrounding waters and airspace. This requires a navy and air force. It does not require an empire.

This distinction matters because much current defence spending is justified by missions that have no connection with the security of these islands. Aircraft carriers are the most obvious example. They are symbols of prestige and instruments of power projection. Their purpose is to carry military force to distant regions. They are useful only if Britain intends to intervene in conflicts far from its shores. They make sense in an imperial framework. They make much less sense in a defensive one.

The same applies to the continued obsession with expeditionary warfare. Every discussion of defence assumes that British forces must remain capable of operating thousands of miles from home. Why? What national interest requires this? What threat to Britain is neutralised by the ability to deploy an armoured brigade to some Levantine desert? These questions are rarely asked because the governing class has become accustomed to thinking of intervention as normal.

Once that assumption is abandoned, Britain’s defence requirements become both modest and achievable. We need a navy capable of controlling our surrounding waters. We need an air force capable of controlling our skies. Beyond that, we need an armed citizen militia.

This proposal is often dismissed because it runs against the instincts of modern governments. Professional military establishments prefer professional soldiers. Governments prefer citizens who are dependent rather than self-reliant. Yet an armed and trained population remains one of the most effective deterrents available to any state. Such a force would also possess advantages that professional armies lack. It would be hard to send abroad. It would therefore be tied by its nature to the defence of Britain. The temptation to use it for ideological adventures would be greatly reduced.

One reason why the Americans were unwilling to invade Iran was that the Iranians are a people in arms. Even the current war in Ukraine demonstrates the difficulty of conquering a population willing and able to resist. Territorial defence remains effective because it is local. It draws strength from attachment to place rather than from abstract geopolitical theories.

An armed citizen militia would cost far less than maintaining large expeditionary forces. It would also be directly connected to the defence of Britain rather than to the ambitions of governments. Its purpose would be territorial security and nothing more than that.

The age of cheap empire is ending. The age of cheap defence is beginning. Technological developments increasingly favour countries that focus on protecting themselves rather than policing others. This is fortunate, because protecting ourselves is exactly what we ought to be doing.

The British people have no quarrel with Iran. They have no quarrel with Russia. They have no quarrel with whatever regional conflict happens this week to excite the foreign policy establishment. What they require from government is prosperity and peace. A defence policy that is really about defence would reflect these priorities. It would abandon fantasies of global management. It would reject the assumption that Britain has some obligation to intervene wherever disorder appears. It would concentrate resources on the defence of Britain itself.

Once we abandon the assumption that Britain must police the world, the requirements of national defence become simple. We need command of our surrounding waters. We need command of our airspace. We need a population capable of resisting occupation. Everything else follows from imperial assumptions that no longer correspond to Britain’s interests or the changing realities of warfare. Everything else belongs to a world that no longer exists.