Huddling in London over the weekend, European leaders declared that they would work to pull together a plan to end the war in Ukraine, but with security guarantees for the country that has been the victim of a full-fledged Russian invasion since February 2022.

The meeting in the United Kingdom followed close on the heels of a disastrous visit to the White House by Ukrainian President Volodymyr Zelenskyy, during which he was publicly berated by US President Donald Trump and Vice President JD Vance for resisting their plans for an unconditional peace plan with Russia.

Trump has made it clear that the US will not provide security guarantees for Ukraine, urging Europe’s military forces to take charge instead.

In meetings with Trump in Washington last week, French President Emmanuel Macron and British Prime Minister Keir Starmer both indicated a willingness to send troops to Ukraine as peacekeepers if a deal to end Russia’s war is reached.

But can Europe meaningfully provide a security cover to Ukraine, without the US backing it? What are Europe’s true security capabilities? How dependent is the region on American support? And what threat does Russia pose?

What role does the US play in European security?

The US has been central to European security since the end of World War II, when it helped create the North Atlantic Treaty Organization (NATO) and deployed hundreds of thousands of soldiers to Europe to challenge Soviet influence. It has maintained this security leadership ever since, while also expanding its global superpower status.

As of July 2024, the US had about 65,000 active-duty soldiers permanently stationed across Europe, along with extensive weaponry, defence systems and other assets vital to NATO, according to the US’s government’s Defense Manpower Data Center.

This includes six pre-positioned weapons stockpiles in Europe, equipped with tanks and armoured vehicles, eight air squadrons, four navy destroyers and an estimated 100 nuclear bombs. Additionally, the US has some 10,000 soldiers on rotational deployment in Poland – a key part of NATO’s eastern flank with Russia.

To fund its military muscle, the US relies on a mammoth defence budget – $860bn in 2024. That’s more than double that of all other combined members of NATO, who are bound to defend each other in the event of an attack.

At the same time, the US has provided the majority of direct military aid to Ukraine since Russia invaded it in 2022, sending approximately $65bn, according to the US State Department. When accounting for other types of assistance, the US had allocated approximately $183bn to the Ukraine response as of September 30, 2024, according to Ukraine Oversight, a website created by the US government to record aid sent to Ukraine. The European Union, for its part, has sent a total of $141bn in aid to Ukraine, including $51bn in military assistance, according to the European Commission.

However, Trump has said it is now time for the US to step back militarily from Europe and wants its allies in the continent to do more heavy lifting.

“Stark strategic realities prevent the United States of America from being primarily focused on the security of Europe,” declared Trump’s Defense Secretary Pete Hegseth at a meeting of NATO allies on February 12. “European allies must lead from the front.”

How strong are NATO’s European allies?

NATO’s European members have a combined 2 million active-duty soldiers, a small portion of whom are assigned directly to serve under the alliance’s command. Turkiye and Poland have the most soldiers, with 481,000 and 216,000 respectively, according to NATO’s latest estimates.

France and Germany follow, with 205,000 and 186,000 soldiers. The UK, which has offered to send peacekeeping forces to Ukraine under a potential peace deal, has 138,000 soldiers. NATO itself has a force of about 40,000 throughout its eastern flank – spanning Estonia, Latvia, Poland, Slovakia, Hungary, Romania and Bulgaria.

Together, NATO’s European allies have some 7,000 aircraft, 6,800 tanks, 2,170 military ships and six aircraft carries, according to the Global Firepower defence index.

How would NATO fare if the US scales down?

Despite its significant military assets, NATO still heavily depends on the US to deter threats in Europe. In the event of a major attack on one of their own, such as by Russia, NATO would likely expect the US to rush hundreds of thousands of additional troops to Europe, according to economic think tank Bruegel.

If Europe can no longer rely on this support, enhanced by Washington’s advanced military technology and infrastructure, Bruegel estimates the continent would need to create 50 new brigades, each consisting of thousands of soldiers, to fill the gap.

Concerned, European states are feeling the pressure to up their defence spending.

Last week, the United Kingdom announced it would increase defence spending to 2.5 percent of the gross domestic product (GDP) by 2027. British Prime Minister Keir Starmer said this would add some $16bn every year to the defence budget, which currently stands at $68bn. “This government will begin the biggest sustained increase in defence spending since the end of the Cold War,” Starmer told parliament.

Germany had announced a special fund of more than $100bn to upgrade and strengthen its military in the wake of the Russian invasion of Ukraine in 2022, adding to its annual defence budget of some $52bn. Last year, the country’s defence budget hit the 2 percent of GDP for the first time since the end of the Cold War as part of a NATO target set in 2014 following Russia’s annexation of Ukraine’s Crimea. Germany’s presumptive next chancellor, Friedrich Merz, in a December speech stressed that the military would need “at least $84bn a year” in the future.

Following Russia’s 2022 invasion of Ukraine, NATO allies across Europe and Canada increased their spending by an unprecedented 18 percent. Currently, 22 of Europe’s 30 European NATO members spend at least 2 percent of their GDP on defence, as per their 2023 pledge.

However, Trump has argued that is not nearly enough, calling for the states to boost defence spending to at least 5 percent of GDP.

NATO Secretary-General Mark Rutte has acknowledged Europe’s need to invest more. “We have not paid enough over the last 40 years, particularly since the Berlin Wall came down,” Rutte told Politico on the sidelines of the Munich Security Conference on February 15. “The US is rightly asking for a rebalancing of that. It’s totally logical.”

How does Russia view NATO?

Russia has cited NATO’s expansion as one of its justifications for invading Ukraine. Since its founding in 1949, NATO has grown from 12 to 32 members, steadily moving eastward towards Russia’s borders. Currently, six NATO members – four of which joined since the turn of the millennium – border Russia, including Finland, Latvia, Estonia and Lithuania.

To keep the Western military alliance at bay, Moscow has demanded that Ukraine, which has long sought NATO membership, be kept out of the grouping.

“Otherwise, this problem will continue to poison the atmosphere on the European continent,” said Russia’s Ministry of Foreign Affairs spokeswoman Maria Zakharova on February 18. Trump’s administration, pushing for a quick end to the war, has said NATO membership is not “realistic” for Ukraine.

But western European states view Russia’s aggression as a reason to strengthen the bloc. Since the end of the Cold War, Russia, the world’s largest nuclear power, has invaded or occupied parts of several nearby countries – Moldova, Georgia and most recently Ukraine.

Russia’s direct military intervention in Moldova in the early 1990s helped Russian-aligned separatists gain de facto control of the breakaway region of Transnistria. And Russia’s blistering invasion of Georgia in 2008 dealt a heavy blow to Tbilisi and complicated its ties with the West.

Since the 2022 invasion of Ukraine, NATO has grown: Previously neutral Finland and Sweden have both joined the alliance over the past two years.

How strong is Russia’s military?

Currently, Russia has at least 1.32 million active-duty soldiers, hundreds of thousands of whom are fighting in Ukraine. Moscow had previously stationed about 12,000 soldiers in Kaliningrad, its westernmost enclave, sandwiched between NATO members Poland and Lithuania. However, most of these forces were reportedly redeployed to Ukraine earlier in the conflict.

Russia also operates dozens of overseas military facilities, most located in former Soviet states. As of 2024, this includes at least two major bases in Belarus, two in Kazakhstan, two in Armenia, two in the disputed Georgian territories of South Ossetia and Abkhazia, and one base each in Kyrgyzstan, Tajikistan, Kazakhstan and Moldova’s breakaway region of Transnistria, according to the Georgian Foundation for Strategic and International Studies. The largest of these facilities is the 201st military base in Dushanbe, Tajikistan, which as of 2022 had an estimated 7,000 Russian soldiers.

In terms of military assets, Russia has 4,292 aircraft, 5,750 tanks, 449 military ships and one aircraft carrier, according to Global Firepower.

While this capacity does not match NATO’s combined strength, it would present a tougher test if the US were to step back, as Trump has called for.

“Europeans need to wake up,” said EU foreign policy chief Kaja Kallas at a conference of the European Defence Agency on January 22. The continent’s “failure to invest in military capabilities”, she said, “sends a dangerous signal to the aggressor. Weakness invites them in.”