European leaders have asked the question what must Europe do to defend itself if America withdraws its support from Nato and returned the answer spend more money. But how much is enough?
With US President Donald Trump cutting off military aid to Ukraine and strong signals from Washington that it might no longer support European countries in a war, the continent knows it now has to move fast to build up its armies.
If America is not present in a future war with Russia, that amounts to 300,000 extra soldiers being required, 1,400 more tanks and a swift increase in spending by $250 billion, according to analysts. At an emergency EU meeting in Brussels on Thursday, leaders thrashed out how to finance a long-term €800 billion ($870 billion) defence package, as Russia ramped up its strikes on Ukraine’s energy infrastructure.
Even if America enforces peace on Ukraine, Moscow’s soaring war economy would see the country very rapidly rearm. If the race to military deterrence in Europe was a 100-metre sprint, many conclude that Russia would be halfway down the track with Europe yet to fly out of the blocks.

Significant disadvantage
If Ukraine war ends and Europe fails to rearm at Russia’s pace it would be “at a significant disadvantage in a high-intensity fight”, warned former US general Gordon “Skip” Davis of Washington's Centre for European Policy Analysis (CEPA).
Across the board, there are key American assets, from artillery, air defence, intelligence, strategic air lift and electronic warfare embedded in Nato.
Other Nato countries have some of the above but not enough to fight it alone as they “are lacking most of the high-readiness force corps the allies have”, said Major Gen Davis, who was the alliance’s deputy assistant Secretary General.

Finding the extra 300,000 troops – the equivalent of 50 new European brigades, equipping and training them is a huge undertaking in a time frame to match Russia, which could be as short as two years.
Indeed, the war might end earlier than expected, with Ukrainian President Volodymyr Zelenskyy heading to Saudi Arabia on Monday to discuss with America a potential peace plan.
Credible force?
The reality is that this year Russian defence spending could rise to 8 per cent of GDP, while some European countries are still struggling to reach the agreed benchmark of 2 per cent.
A Goldman Sachs report has projected an $84 billion boost to defence budgets across the EU alone by 2027. It says it expects the bloc's spending on defence to rise from 1.8 per cent of GDP in 2024 to 2.4 per cent in two years. There is an upside in that very dollar spent on defence should boost GDP by 50 cents. It also notes that an equipment build up means that one third of the bigger budgets is going on new kit.
The equipment gap is vast. For Nato to defend, for example, the Baltics to deter a Russian attack it would need to assemble a force of 1,400 tanks, 2,000 infantry fighting vehicles and 700 artillery pieces, a report from the think tank Brueghel stated. A minimum stockpile of one million 155mm artillery rounds would also be needed, that would last 90 days of high intensity combat.
But that hardware was currently beyond Europe’s reach with the think tank stating this was “more combat power than currently exists in the French, German, Italian and British land forces combined”.

Holes in alliance
America stepping back, said Brig Ben Barry of the IISS think tank, was going to make war planning assumptions very different, with the 100,000 troops of US III Corps and the expected 200,000 fast reinforcements from across the Atlantic no longer available.
“Military planners would expect US armoured divisions, ships and aircraft but if those don't come any more, Europe's got a bit of a problem,” Brig Barry said. “Europe's military position would considerably worsen and this would greatly weaken Nato's deterrence value.”
Part of that is the nuclear umbrella that is mostly provided by US tactical nuclear weapons based in such countries as Germany, Italy and Belgium. Their withdrawal would leave Europe exposed. While France and Britain both have a strategic nuclear submarine fleet, only the French have a handful of ASMP tactical nuclear cruise missiles.

While the costs to rearm would be large they are not unmanageable, especially if Germany's arms build up amounts to at least half of the target figure. Michael Schoellhorn, the head of Airbus Defence and Space, told a German newspaper that Berlin's role would be key. "Europe is under threat and too weak in this new era of history – both economically and militarily," he said.
Even Britain’s recent increase to 2.5 per cent of GDP has been recognised as insufficient. Armed Forces Minister Luke Pollard admitted on Thursday that the amount was “just the starting gun” in a race to modernisation.
Analysts believe that making up for the shortfalls would require Nato countries to spend 4 per cent on defence, doubling many budgets and taking spending back to Cold War levels. The US currently spends 3.4 per cent on its armed forces.
Precision deficit
What Europe most fundamentally lacks, and what Ukraine has demonstrably proven to be highly effective, is the modern US precision missiles that can devastate an invading force.
These are the HIMARS and ATACMS weapons that the US has in large supply, unlike the UK and France's equivalent, the Storm Shadow or SCALP cruise missiles.
Another deficit is an air force heavy bombing capability, a major space satellite force for surveillance and interception, as well as signals intelligence aircraft. While the US has 17 Rivet Joint ISR (intelligence, surveillance, reconnaissance) aircraft, Europe would have to rely on Britain’s three Rivet Joints.

The continent does have a lot of fourth-generation jets, able to strike targets deep inland or take out air defences, but it lacks the ammunition stockpile necessary for a sustained war. That could be rapidly remedied if governments are willing to place big orders with the major defence companies.
Europe’s many different armies and defence companies would have to coalesce like never before to build the same kit, to reduce costs and help conformity as having different weapons systems can create logistical hold-ups and confusion.
Its distance behind Russia is exemplified by Moscow’s ability to produce three million artillery shells last year while Europe struggled to get to one million.
Furthermore, drones utterly dominate the war, with Ukraine said to field up to four million this year, but both Europe and America appear far behind.
General experience
Another major deficiency will be leadership experience. The top posts in Nato are mostly held by US officers who have the ability to run a corps-sized force of up to 50,000 troops.
It is also questionable whether Europe's top staff officers, most likely from France and Britain, would be, in current circumstances, able to run an air campaign equivalent to the Israelis in Gaza.

But Europe might currently have enough tanks, aircraft and artillery to fight Russia, and these are generally of a much superior class, argued military analyst Tim Ripley. The continent also has the money and industrial capacity to make more, especially as collectively its economy “dwarfed Russia’s”.
He also argued that after massive losses of tanks and armoured vehicles, potentially more than 10,000, the Kremlin’s ability for “mass and manoeuvre is severely constrained”.
But it is not just US hardware that provides a major deterrent to Russian territorial expansions, said Brig Barry. “It's America's very presence in Europe that reinforces deterrence, by virtue of there being US boots on the ground and behind them a significant nuclear deterrent,” he said.