NATO’s 75th anniversary coincided with the US announcement to reduce or transform the presence of US army units in European theatre. What caused this process, which crises it provokes and the possible consequences for Europe.
In February 2025, US Defense Secretary Pete Hegeset, at a meeting with NATO Defense Ministers, made it clear that the United States cannot prioritize European security.
He called on the European allies to assume a greater share of defence spending and acknowledged that the US presence could be reconsidered.
In parallel, there were reports about the Pentagon’s plans to start a «audit» of the US contingent. According to these plans, between 10,000 and 50,000 US troops could be withdrawn from Europe, and the key role of the US in the NATO structure – in particular, the post of Supreme Commander-in-Chief of the Unified Forces in Europe – could be revised.
With about 85,000 US troops (including rotations) currently deployed in Europe, the very nature of the discussion sends alarm signals, as their presence is more important than mere numbers.
The key reasons for this shift are related to changing global priorities and Washington’s internal strategic calculations.
Above all, the US’s attention is increasingly shifting to the Asia-Pacific region, where rivalry with China is intensifying and new geostrategic lines of confrontation are forming.
According to analysts, this was one of the key arguments for reallocating military resources and revising US military presence in Europe.
An additional element of pressure was Washington’s demand that NATO allies increase defense spending to as much as 5% of GDP.
And in the face of economic difficulties and social tensions, not all European governments are prepared for such a massive increase in military budgets.
However, the US insists that without this redistribution of the financial burden, the Alliance will not be able to function effectively.
Another factor is the desire of the Pentagon to optimize its logistics and military contingent. Reduction of rotations, reduction in the number of units temporarily deployed and possible withdrawal from some support bases.
This restructuring reduces costs, but at the same time reduces the US military presence on the European continent.
An important signal was the announcement on 29 October 2025 that the US had announced the withdrawal of one brigade of about 3,000 troops from the eastern flank of NATO, including the territories of Romania, Bulgaria, Hungary and Slovakia.
Even if the decision is preceded by lengthy preparations, the announcement itself has already created considerable tension within the alliance and raised questions about whether transatlantic security guarantees are sustainable.
Within NATO today, a crisis of confidence, willingness to redistribute the financial burden, and growing tension over collective security responsibilities are increasingly evident.
The main challenge for the alliance was trust.
The question is increasingly raised: can we still rely on the US as the main guarantor of security? When US officials speak of the need to «share the burden», many allies perceive it not as a call for partnership, but as a signal that earlier guarantees should be weakened.
Experts note that if the US ceases to perform its primary function as a security guarantor, an alliance crisis of confidence will inevitably start. This uncertainty erodes the foundations of transatlantic solidarity, creating an atmosphere of caution and mutual grievances.
The issue of cost allocation is equally pressing. Washington is demanding that European countries increase their defense budgets to 3-4%, and in the long run to 5% of GDP.
But many governments are not prepared for such costs because of domestic social programs, economic constraints, and political considerations.
According to the European Parliament, in 2024 the average level of defense spending among NATO member states was only about 1.9% of GDP. This irritates Washington and forms a polarization of opinion about the US presence in Europe.
Against the background of these processes, the idea of forming the so-called «European pillar» of NATO, a concept that assumes that Europe will gradually assume more responsibility for its own defense.
If the United States does indeed begin to gradually reduce its military presence, the structure of the alliance will inevitably be transformed.
The implications of reducing the US military presence in Europe go far beyond a purely military issue. They affect the economy, politics, strategy and even public attitudes within the countries of the alliance.
One of the main risks is the so-called «vulnerability window».
Analysts predict that if the US begins a sudden withdrawal, Europe will need from 226 to 344 m. dollars to replace the American systems.
These are years of hard work, as the European armies have yet to compensate for key functions provided by the United States that depend on American technology and infrastructure, such as intelligence, air refuelling systems, missile defense, Radar networks and operational logistics.
Thus, there is a risk between the moment of the reduction of the American presence and the time when Europe will be able to fill the gaps, the «window of vulnerability».
During this period, the continent will be inadequately equipped and poorly coordinated, and its defense capacity is insufficient. If European forces are unable to carry out key tasks independently, NATO risks becoming a structure with varying speeds of development, where some states become active participants and others passive observers.
This will lead to an institutional divide and weaken the overall effectiveness of the alliance. The geopolitical consequences of the reduction of the American presence will be particularly acute on NATO’s eastern flank, in the Baltic states, Poland and Romania.
It is here that the threat from Russia is considered to be most real. According to experts, the reduction of US troops in the region could be perceived by Moscow as a sign of weakness and create an incentive to increase pressure. In the long term, this could lead either to an increase in bilateral deals with Russia, which would undermine NATO unity, or to a new spiral of militarisation and tension in the region. The domestic political consequences are no less important.
Public sentiment in European countries may become more negative towards increased defence spending, especially if the population perceives the US withdrawal as a sign of weakening alliance commitments. Against this backdrop, the political debate intensifies: ‘Why should we increase spending if America is leaving?’ Such perceptions may complicate consensus within governments and parliaments.
The situation on the US side is also unclear. Opponents of hasty reductions are already making their voices heard in the US Congress. Representatives of both parties insist on maintaining the American contingent in Europe, rightly considering it a strategic element of deterrence and influence.
Thus, NATO member states find themselves in a dual position – between American pressure demanding greater independence and internal political resistance unwilling to increase military spending ‘forever.’
At the same time, numerous official statements emphasise that this is not about the US ‘withdrawing’ from Europe in the usual sense, but merely about a redistribution of forces and resources.
The official rhetoric is built around the idea of strategic optimisation, not a departure from allied commitments. American representatives call this a ‘planned adjustment’ and assure allies that there will be no ‘surprises.’
The main problem is that Europe does not yet have the necessary capacity to quickly fill the gap left by the American correction. Chronic differences in defence budgets, uneven development of military technology and dependence on American logistics make it impossible to quickly ‘replace’ the US.
Even if European states agree to increase defence spending, it will take years to create comparable intelligence, command and strategic mobility systems.
Europe is facing a moment of strategic decisions. Either it will be able to take up the challenge, or it will find itself unprepared for the new conditions.
If the continent does not become active, but only reactive, the ‘window of vulnerability’ may become inevitable. The alliance is entering a phase where someone must take the initiative in the transition from old to new patterns.
Europe faces a choice: either to act as an executor or a partner, or, if it is not ready, to watch history unfold without its participation.