How long will it take Europe to rearm?

Re-arming Europe to a level broadly equivalent to that of the United States, measured proportionately to gross domestic product, is not simply a question of budgetary ambition. It is a problem of industrial depth, political culture, institutional architecture and time. Even if European governments were to decide tomorrow that parity with the United States was an overriding strategic necessity, the pathway to that goal would extend well beyond a single electoral cycle and, in many sectors, beyond a decade.

At present, the United States spends roughly 3.3 to 3.5 per cent of her GDP on defence, translating into annual military expenditure of around USD 850 billion. Europe, taken as a whole and including non-EU NATO members such as the United Kingdom and Norway, spends closer to 2 per cent of GDP, with wide variation. Poland and the Baltic states are now just short of 5 per cent, the United Kingdom stands at around 2.3 per cent, France at approximately 2.1 per cent and Germany only recently crossed the 2 per cent threshold after decades of underinvestment. On a GDP-weighted basis, Europe would need to increase defence expenditure by roughly one additional percentage point of GDP to reach a United States equivalent level.

In purely fiscal terms, this looks deceptively achievable. For Europe as a whole, that additional one per cent represents something in the region of EUR 200 to 250 billion per year. Over ten years, this would amount to a cumulative investment of roughly EUR 2 to 2.5 trillion. The European Union alone has mobilised sums of this magnitude in response to the Covid-19 pandemic. However defence spending is not stimulus spending. It does not translate automatically into deployable capability, particularly when industrial capacity has been allowed to atrophy.

The first constraint is industrial. The United States retains a defence-industrial base designed for sustained large-scale production. She can produce combat aircraft, long-range missiles, precision-guided munitions and armoured vehicles at scale, with comparatively short lead times. Europe cannot. The war in Ukraine has revealed that even the replenishment of basic artillery ammunition stretches European production lines to their limits. Expanding these lines is not a matter of months. New factories require planning permission, skilled labour, supply chains for explosives and specialised components and, critically, guaranteed long-term contracts that justify the capital investment. From decision to full-rate production, five to seven years is a realistic estimate for most heavy munitions sectors.

The second constraint is structural fragmentation. The United States operates a largely unified procurement system under the Department of Defense (now renamed the Department of War). Europe operates more than two dozen national procurement systems, each with its own requirements, political sensitivities and industrial champions. The result is duplication, inefficiency and delay. Europe fields multiple main battle tanks, infantry fighting vehicles and combat aircraft types where the United States fields one or two. Even if Europe were to spend at United States levels tomorrow, the conversion of money into coherent capability would remain slower unless procurement is rationalised. Achieving this rationalisation is a political task that may itself take many years.

The United Kingdom occupies a distinctive position within this picture. She retains a nuclear deterrent, global power projection capabilities and a defence-industrial base that is still comparatively sophisticated, particularly in naval construction, aerospace and intelligence systems. However, she has also suffered from decades of underinvestment, hollowing out and an over-reliance on exquisite but small force structures. Even at increased spending levels, the United Kingdom would need at least five to ten years to rebuild mass in areas such as land forces, air defence and munitions stockpiles. Her contribution to a re-armed Europe would be strategically significant, but not instantaneous.

Personnel represents a third and often underestimated bottleneck. The United States benefits from a large standing force, deep reserves and a military culture that has normalised high operational rhythm for decades. Europe has moved in the opposite direction. Conscription has been abolished or hollowed out in many states, reserve systems are weak and military careers compete poorly with civilian alternatives. Rebuilding manpower is slower than buying equipment. Training a competent armoured brigade, air defence unit or naval crew takes years, not months. Even if European states were to reintroduce or expand conscription, the benefits would only become visible towards the end of the 2020s or early 2030s.

There is also the question of technology and integration. The United States spends a far higher proportion of her defence budget on research, development, intelligence and enablers such as space assets, strategic lift and command-and-control systems. Europe could match spending levels and still fall short in these areas unless she deliberately prioritises them. Developing indigenous European alternatives to United States satellite networks, missile defence architectures and large-scale logistics would likely require at least a decade of sustained effort.

Taking all these factors together, a realistic timeline emerges. If Europe were to commit collectively to defence spending at United States-equivalent levels from the mid-2020s onward, she could plausibly rebuild ammunition stocks, basic land warfare mass and short-range air defence by the early 2030s. More complex capabilities, such as long-range strike, integrated missile defence and sustained high-intensity expeditionary warfare, would follow later in that decade. Full-spectrum parity with the United States, even on a GDP-proportionate basis, would likely not be achievable before the mid to late 2030s, and even then only if political commitment proved durable.

The strategic implication is sobering. Europe cannot re-arm quickly enough to replace the United States as a security guarantor in the short term. Even under the most optimistic assumptions, she faces a decade of vulnerability during which deterrence depends upon American engagement and the credible threat of escalation. This reality does not argue against European re-armament. On the contrary, it underlines its urgency. The longer Europe delays, the further the horizon of strategic autonomy recedes.

Re-arming Europe to United States-equivalent levels is therefore less a sprint than a generational project. It requires not only money, but patience, coordination and a political willingness to accept that security, like welfare, is a permanent function of the state. Whether Europe can sustain that willingness over ten to fifteen years will determine not only her military balance with the United States, but her capacity to resist coercion in a century that is already proving far more violent than the last.