Story: Erkin Öncan | Curated by: Ömer Sirkecioğlu
A new report by the International Institute for Strategic Studies (IISS), titled "Defending Europe Without the United States: Costs and Consequences," outlines the financial and strategic implications for Europe if the U.S. withdraws from NATO. Founded in 1958 and based in London, IISS is renowned for its analyses on global security and defense, often referenced by NATO, the United Nations, and national defense ministries.
According to the report authored by Ben Barry, Douglas Barrie, Henry Boyd, Nick Childs, Michael Gjerstad, James Hackett, Fenella McGerty, Ben Schreer, and Tom Waldwyn, Europe would need to allocate $1 trillion over the next 25 years to maintain its defense capabilities without U.S. support.
This would require increasing defense spending to 3% of the continent's GDP.
The projected expenditures are distributed across several key areas in anticipation of a scenario where 128,000 U.S. troops, along with their equipment, withdraw from Europe by 2027. Approximately 50% of the budget is allocated to military equipment, including tanks, armored vehicles, aircraft, ships, missiles, and drones. Another 25% is dedicated to intelligence operations, space forces, and command-control systems. Meanwhile, 20% is earmarked for personnel training, equipment, and logistics support. Finally, 15% of the projected spending is planned for investments in the defense industry and foreign procurements.
The 32-page report identifies two primary challenges for Europe.
Firstly, the report notes that “Russia's economy has shifted to a wartime footing, with its defense industry operating at full capacity. Even if conflicts in Ukraine cease, Russia could rapidly rebuild its military strength, posing a renewed threat to NATO-Europe.”
Secondly, “The report highlights a changing U.S. stance, citing statements from President Donald Trump and Defense Secretary Pete Hegseth in 2025, emphasizing that Europe should take greater responsibility for its defense. This indicates a U.S. strategic pivot towards the Pacific, necessitating Europe to develop capabilities to deter Russian aggression independently.”
The IISS report assumes a mid-2025 ceasefire in Ukraine, followed by a gradual U.S. withdrawal from NATO and European deployments. It assesses factors such as Russia's potential to reconstitute its military threat post-ceasefire, current U.S. contributions to NATO, Europe's readiness levels, equipment gaps, financial costs, timelines, and leadership dynamics.
The first section of the report focuses on the threat Russia poses to Europe. According to the IISS, Russia remains “the principal military threat to the Euro-Atlantic area.”
The report argues that a key task for European allies is to determine how quickly Russia could regenerate its military forces once active hostilities have ceased.
The report also highlights perspectives on Russia’s “potential threat” from various European military and intelligence officials:
UK Chief of Defense Staff Admiral Tony Radakin estimates it could take Russia five years to restore its military to February 2022 levels, with an additional five years to address vulnerabilities exposed by the war.
Estonia's Foreign Intelligence Service warns that within the next decade, Russia could pose a significant threat to NATO, even with outdated technology, by mobilizing a large-scale military force reminiscent of the Soviet era.
Norwegian Chief of Defense General Eirik Kristoffersen suggests that Europe has a two to three-year window to prepare for potential threats.
Denmark's Defense Intelligence Service assesses that Russia could initiate localized conflicts within six months post-ceasefire, regional wars in the Baltic within two years, and large-scale attacks across Europe within five years.
The IISS analysts concur with Denmark's assessment, stating:
"Despite challenges, Russia could pose a significant military challenge to NATO allies, especially the Baltic states, as early as 2027. By then, Russia may have replenished its ground forces to near February 2022 levels, while its air and naval assets remain largely intact. Russia's capacity for rapid military regeneration should not be underestimated, given its wartime economy and foreign equipment acquisitions."
The report shares detailed data on Russia's defense expenditures, revealing that its military spending surged by a real 41.9% from 2023 to 2024, reaching 13.1 trillion rubles (approximately $145.9 billion USD, or $462 billion in purchasing power parity). This figure now accounts for 6.7% of Russia’s GDP, more than double the pre-war average of 2.8%, and is projected to rise further to 7.5% in 2025. The state’s tight grip over its defense industry far exceeds that of its European counterparts.
Europe’s outlook on Russia is summarized with this stark warning:
“Whether Moscow reduces its defense spending after a ceasefire will determine the pace of rearmament. However, since the Kremlin has neither abandoned its strategic goals in Ukraine nor ceased efforts to destabilize Europe, assuming a continued high defense budget is a rational expectation.”
A noticeable fracture within the transatlantic alliance appears in the report when it comes to Ukraine. Unlike the Trump administration, Europe believes that a ceasefire in Ukraine would grant the Kremlin room to regroup:
“A ceasefire will offer Moscow a chance to catch its breath, while simultaneously starting the countdown for Europe. Despite suffering heavy losses in its ground forces, Russia’s swift recovery potential in air and naval capabilities poses a lasting elevation in Europe’s defense alert level.”
The second section of the report focuses on NATO’s strategic planning for a potential large-scale war in Europe, with particular attention to SACEUR, the Supreme Allied Commander Europe.
SACEUR is NATO’s top military authority in Europe, responsible for commanding all allied forces in the transatlantic region. Since the alliance’s founding, the post has been held by a four-star U.S. general or admiral.
The report refers to the "National Capability Targets" developed by NATO military staff based on SACEUR’s requirements and notes that the total force size now deemed necessary to implement defense plans is estimated to be 30–50% larger than before 2022.
While IISS points to new targets expected to be approved at NATO’s ministerial meeting in June 2025, it also highlights a warning from NATO Supreme Allied Commander Transformation, Admiral Pierre Vandier. He noted that the proposed targets would require a 30% increase over previous commitments, yet allies are already falling 30% short of current goals.
There is no official data on the scale of military support the United States would contribute to NATO in the event of a continent-wide war with Russia. However, according to IISS analysts, NATO remains heavily reliant on U.S. strategic intelligence, space and cyber capabilities, and its vast nuclear arsenal, particularly through U.S. European Command (EUCOM):
“In the event of conventional operations in Europe to counter Russian aggression, the U.S. would likely contribute around 128,000 personnel, along with land, sea, and air units.”
The third section of the IISS report focuses on the potential consequences of a U.S. withdrawal from NATO and Europe.
Assuming this scenario, highly complex and time-consuming though it may be, is treated as a real possibility, the simulation presented by IISS experts is divided into two main strands.
In the first scenario, existing U.S. bases, training areas, and military infrastructure in Europe could be sold to host nations or commercial buyers. Surplus ammunition and spare parts might be handed over to European militaries. However, European states would be required to replace the advanced training facilities, teams, and tools currently provided by the U.S. in forward-deployed locations.
The second scenario considers a reduction in U.S. intelligence sharing, which would expose gaps in Europe’s space-based and all-domain Intelligence, Surveillance, and Reconnaissance (ISR) capabilities. This would significantly impair Europe’s ability to detect early signs of a Russian attack and to interpret Russian military plans once hostilities begin.
According to the report, if the U.S. were to fully withdraw from Europe, the financial burden on European countries to replace American capabilities on a one-to-one basis would amount to between $226 billion and $344 billion. This figure excludes the cost of intelligence, space, cyber, and nuclear capabilities.
When accounting for one-time procurement costs and 25-year lifecycle expenses, IISS estimates that fully replacing the U.S. role in NATO’s collective defense would cost Europe close to $1 trillion.
This staggering cost is one of the key reasons for European officials’ anxiety over a possible American exit.
IISS analysts argue that even if Europe could afford the financial burden, its defense industrial base currently lacks the production capacity to meet the demand. The report explains:
“European defense firms have begun expanding capacity, opening new assembly lines and engaging in mergers and acquisitions, but progress is uneven, and many structural issues remain unresolved.”
“Should European allies decide to invest in additional aircraft carriers or nuclear-powered attack submarines (SSNs), delivering them would be a major challenge.”
“In the short term, European manufacturers will struggle to meet the necessary volume of armored vehicles, given current production limitations. Therefore, states must significantly invest in expanding their land systems industries, repurposing facilities from other sectors and striking new deals with long-standing suppliers like the U.S. and Canada, as well as non-European armored and artillery manufacturers.”
The report also points out that because procurement in most European countries is handled at the national level, order volumes remain small compared to the U.S. To address this gap, the IISS recommends pooling orders through international cooperation to achieve economies of scale.
The financial burden of filling that gap, combined with the prospect that Russia could rebuild its ground forces by 2027 if a ceasefire is reached in Ukraine, has set off alarm bells across the continent.
Under current conditions, even scaling Europe’s defense industry up to the level of Russia’s so-called “war economy” would fall short. Structural hurdles, ranging from workforce shortages to production bottlenecks, fragile supply chains, and limited financing, remain daunting. Take, for example, a single figure from the report: ordering an additional 400 fighter jets alone would overwhelm the world’s current production capacity.
Escaping this bleak scenario will require Europe to go far beyond current commitments. Defense spending will have to increase further. Joint (multinational) procurement of weapons systems must become the norm. Public financing will be needed to ease the fiscal burden, and governments will need to persuade their citizens to accept it. Bold financial-industrial initiatives, innovative public-private investment models, and hard choices about spending priorities will all be essential. Yet even if the money is found and capabilities are built, one challenge looms larger than all others: forging genuine political unity and collective will. That may prove the hardest task of all.
Already, aid to Ukraine, at today’s levels, has fueled political turbulence across Europe, where governments are grappling with migration, climate, and economic crises. The rise of the far right, a trend that European capitals are watching with growing unease, is gaining traction by channeling widespread demands for stability and security, and is beginning to topple governments.
