For nearly eight decades, European security has rested on a fundamental assumption: regardless of political disagreements between Washington and its allies, the United States would remain the ultimate guarantor of the continent’s strategic stability. Donald Trump’s return to the White House has profoundly weakened that certainty. The war in Ukraine, relations with Moscow, and growing transatlantic tensions reveal a transformation extending far beyond the decisions of a single president. Europe is discovering that its security depends on a power whose priorities no longer necessarily coincide with its own.

There was a time when disagreements between Europeans and Americans appeared to be part of the ordinary functioning of the Atlantic Alliance. Crises followed one another, presidents changed, European governments protested against certain decisions taken in Washington, yet one conviction remained intact: when confronted with a major strategic threat, the United States would stand alongside Europe. This certainty represented much more than a military commitment. It shaped budgetary decisions, industrial policies, defense doctrines, and ultimately the way Europeans understood their place in the world.

Today, that entire strategic framework is becoming increasingly uncertain. The question is no longer simply how many American troops will remain stationed on the continent, how many air defense systems Washington will provide to Ukraine, or what financial contribution European NATO members will be expected to make. It has become considerably more fundamental: can an alliance continue to perform its historical function when its leading power no longer necessarily regards the security of its partners as a permanent strategic interest?

The answer does not depend exclusively on Donald Trump. The American president is accelerating a transformation whose origins go back several decades. Yet he gives it a particularly explicit political expression by placing relations between allies within a framework of negotiation, reciprocal concessions, and competing national interests. Where Europe once saw a stable system of guarantees, Washington increasingly appears to see a collection of commitments whose terms can be reassessed.

This does not mean that the United States has abandoned Europe. It means something potentially more destabilizing: Europeans can no longer regard American protection as a permanent condition independent of political circumstances.

A Dependency That Became a Continental Order

Modern Europe developed within a security architecture whose foundations were established after the Second World War. The creation of the North Atlantic Treaty Organization in 1949 institutionalized American engagement, while the deployment of conventional and nuclear forces gradually transformed the United States into the central pillar of the European strategic balance.

Article 5 of the North Atlantic Treaty establishes that an armed attack against one member shall be considered an attack against them all. However, it does not prescribe an identical or automatic military response from every ally. Each member takes the action it considers necessary, including the possible use of armed force. The credibility of collective defense therefore rests as much on political determination as on military capabilities.

During the Cold War, that determination appeared inseparable from American national interests. Defending Western Europe allowed Washington to contain the Soviet Union, protect its economic interests, and preserve a global balance favorable to American power. The commitment was not an act of generosity. It reflected a profound convergence of strategic interests.

The disappearance of the Soviet Union did not lead to the dismantling of this architecture. On the contrary, NATO expanded, European institutions strengthened, and many governments progressively reduced the importance of defense in their national budgetary priorities. The possibility of a major conventional war on the continent seemed sufficiently remote to justify a lasting redistribution of public resources.

This development produced a paradox. Europe accumulated one of the world's largest concentrations of wealth, industrial capabilities, and scientific expertise while maintaining substantial dependence on American military assets.

Strategic intelligence, space capabilities, heavy airlift, aerial refueling, certain missile defense systems, integrated command structures, and extended nuclear deterrence remain areas in which the American contribution would be extremely difficult to replace in the short term.

European dependence therefore cannot be explained solely by insufficient military expenditure. It is the product of a historical distribution of strategic responsibilities: the United States provided a decisive share of the means of protection, while European countries developed their economies within a relatively predictable security environment.

This arrangement was not necessarily irrational. It rested on the assumption that American and European interests would remain sufficiently aligned to ensure its continuity.

That assumption is precisely what is now being challenged.

Washington No Longer Sees the World Primarily Through Europe

The reorientation of American strategic priorities began long before Donald Trump's return. Under Barack Obama, the strategic pivot toward Asia already reflected the conviction that the defining geopolitical challenges of the twenty-first century would increasingly emerge in the Indo-Pacific.

China's rise, technological competition, critical supply chains, and maritime security in Asia gradually absorbed a growing share of American strategic attention.

This transformation continued across successive administrations. Despite their political differences, Democrats and Republicans increasingly recognized the importance of the rivalry between Washington and Beijing. Industrial policies, technological restrictions, and efforts to secure strategic supply chains reinforced that reorientation.

Europe remains economically and militarily important, but it no longer necessarily occupies the leading position in Washington's hierarchy of strategic concerns.

Donald Trump introduces an additional rupture by questioning the political foundations of Western solidarity.

In his understanding of international relations, alliances should not merely generate broad strategic advantages. They should also produce measurable benefits and immediate reciprocal commitments that can be justified to American voters.

Allied military expenditure consequently becomes an instrument of negotiation. Commercial relations can be treated separately from security commitments, and sometimes brought into conflict with them. Diplomatic disagreements are no longer systematically contained by a shared determination to preserve Western political unity.

This approach transforms the nature of European uncertainty.

Previously, European governments could anticipate disagreements over methods while assuming a fundamental convergence of objectives. They must now contemplate the possibility that Washington will define its strategic goals without assigning European interests the same importance in its calculations.

The risk is not limited to military withdrawal. It lies in the unpredictability of the commitment itself.

A security guarantee does not have to be formally revoked to lose part of its effectiveness. It is enough for a potential adversary to begin questioning whether the guarantor would actually fulfill its obligations.

Ukraine as the Test of a Strategic Divergence

The war in Ukraine has become the principal testing ground for this transformation.

Since Russia's full-scale invasion in February 2022, the United States has played an essential role in the military, financial, and diplomatic support provided to Kyiv.

American assistance has included equipment, ammunition, intelligence, and defensive capabilities whose strategic importance cannot be measured solely through their financial value.

European countries have also mobilized considerable resources, but the distribution of contributions has exposed specializations and dependencies that cannot be corrected quickly.

Above all, the Ukrainian conflict reveals the possibility of a divergence in the definition of security objectives.

For European countries most directly exposed to Russian military power, the outcome of the war concerns the future stability of the continent. Borders, the credibility of Western commitments, and the risk of further military operations represent immediate security concerns.

For Washington, the conflict can also be assessed through other considerations: its budgetary cost, the military resources it absorbs, the possibility of negotiations with Moscow, and its implications for strategic competition with Beijing.

These interests are not necessarily incompatible. But they are not identical.

An American administration may prioritize reaching a diplomatic agreement quickly, while some European governments believe that a settlement without sufficiently credible guarantees would create the conditions for another confrontation.

Conversely, Washington may conclude that an indefinitely prolonged conflict diverts resources from other strategic priorities.

The issue therefore extends beyond the question of Ukrainian territory.

It concerns the definition of a sustainable peace, the mechanisms required to guarantee it, and the distribution of responsibilities between the United States and Europe.

It would be inaccurate to equate every American negotiation with Moscow with an endorsement of Russian objectives. Diplomacy between rival powers does not necessarily imply political convergence.

However, a settlement negotiated without credible guarantees for Ukraine, or without meaningful European participation in defining the resulting security order, could profoundly weaken continental stability.

This distinction is fundamental.

The problem is not that Washington might negotiate with Moscow. It is that European security interests could become merely one variable among several in negotiations whose most important decisions are taken elsewhere.

Russia and the Strategic Value of Western Uncertainty

For Moscow, transatlantic disagreements represent a strategic opportunity, regardless of the American administration's actual intentions.

For decades, Russia has challenged aspects of the European security order established after the Cold War. NATO enlargement, Western military deployments near Russian territory, and Ukraine's geopolitical orientation occupy a central position in Russian strategic discourse.

These arguments do not justify the invasion of Ukraine or the violation of its sovereignty. They nevertheless help explain why Moscow attaches particular importance to the political cohesion of the Atlantic Alliance.

NATO's strength does not rest exclusively on the combined military budgets of its members. It depends on their ability to act collectively, anticipate crises, and convince potential adversaries that commitments will be honored.

An alliance possessing substantial military resources but uncertain about its members' reciprocal obligations can become less effective as a deterrent than a smaller force operating under a clear and credible decision-making structure.

In this environment, ambiguity in Washington can have consequences disproportionate to any immediate change in military deployments.

It encourages attempts to exploit divisions, increases pressure on exposed European states, and forces governments to devote greater resources to preparing for scenarios previously considered improbable.

This does not mean Russia possesses unlimited capacity for confrontation.

The war in Ukraine has demonstrated the human, economic, and industrial costs of prolonged military operations. Sanctions, equipment losses, and technological constraints affect Russia's longer-term military prospects.

Yet deterrence also depends on perceptions of risk.

A Russia facing substantial material constraints may nevertheless seek to exploit political uncertainty among its opponents.

The declining predictability of American engagement therefore changes strategic calculations across Europe, even without an immediate reduction in NATO forces.

European Rearmament and Its Contradictions

European governments have begun responding to the deterioration of their security environment.

Russia's invasion of Ukraine accelerated military spending, the replenishment of ammunition stocks, and investment in defense capabilities.

According to NATO estimates published in 2024, military expenditure by European allies and Canada exceeded $480 billion, measured at constant 2021 prices and exchange rates. This represented a real increase of nearly 20% compared with the previous year.

At that time, NATO estimated that 22 of its 32 members had reached the defense spending benchmark of 2% of gross domestic product.

The transformation subsequently accelerated. At the Hague summit in June 2025, NATO allies committed to investing 5% of GDP annually in defense and defense-related security by 2035, including at least 3.5% for core defense requirements and up to 1.5% for broader security-related expenditure.

The new commitment represents a substantial change in the Alliance's financial ambitions.

Yet higher spending does not automatically produce European strategic autonomy.

The first difficulty lies in the fragmentation of decision-making.

European states maintain separate national budgets, different military doctrines, competing defense industries, and sometimes divergent geographical priorities.

Poland and the Baltic states attach immediate importance to the Russian threat. France emphasizes the need to preserve an independent capacity for strategic action. Germany must reconcile military modernization with the constraints of its economic model and political institutions. Mediterranean countries must also account for instability in Africa, the Middle East, and surrounding maritime regions.

These differences do not make collective defense impossible. They do, however, complicate the development of a coherent industrial and operational strategy.

The second difficulty is industrial.

Increasing defense budgets does not automatically increase the number of weapons available.

Producing artillery shells, missiles, air defense systems, and armored vehicles requires investment, predictable orders, secure supply chains, and time.

European defense industries possess substantial expertise, but manufacturing capacity cannot be multiplied overnight.

Companies hesitate to make major investments without long-term procurement commitments. Governments, meanwhile, frequently seek to protect national industrial champions.

This creates a contradiction: Europe wants to reduce its strategic dependence, yet part of its additional military spending may reinforce reliance on external suppliers, particularly American companies.

The third difficulty concerns strategic enabling capabilities.

A modern military force cannot be measured solely by its combat aircraft, tanks, or personnel.

It depends on complex supporting systems: satellites, intelligence, secure communications, logistics, electronic warfare, missile defense, surveillance, and command structures.

In several of these areas, the American contribution remains decisive.

Replacing it would require not only substantial financial resources but also a profound reorganization of European military institutions.

The central challenge is therefore not simply the availability of resources. It is the ability to transform those resources into coherent collective power.

The Nuclear Deterrence Dilemma

The nuclear question illustrates the limits of European strategic autonomy particularly clearly.

For decades, the United States has provided the principal framework for extended nuclear deterrence within NATO.

The purpose of this guarantee is to convince potential adversaries that a major attack against an ally could provoke a response whose consequences would greatly exceed any expected strategic gains.

France and the United Kingdom possess independent nuclear forces.

However, their doctrines, command structures, and capabilities do not constitute a straightforward replacement for the American system.

French nuclear deterrence is based on sovereign presidential authority and the protection of the nation's vital interests.

French doctrine recognizes that these interests possess a European dimension, but it does not establish an automatic nuclear guarantee equivalent to the arrangements associated with the Atlantic Alliance.

The United Kingdom also maintains a national nuclear deterrent, although its technological and strategic cooperation with the United States remains particularly extensive.

Imagining that French and British arsenals could rapidly replace the American nuclear guarantee would therefore underestimate the political, operational, and doctrinal obstacles.

Who would decide whether nuclear weapons should be employed? Which territories would receive explicit protection? Which political authority would define common vital interests? How would responsibilities be distributed between nuclear and non-nuclear European states?

These questions cannot be resolved through higher military expenditure alone.

They reach the core of political sovereignty and expose a fundamental limitation of European integration.

The continent possesses powerful common economic instruments but lacks a single political authority capable of assuming the full range of strategic decisions associated with sovereign defense.

European military autonomy consequently depends on more than manufacturing new weapons.

It requires a reconsideration of the political structures through which Europe exercises power.

An Economic Power Without Complete Strategic Sovereignty

The European Union represents one of the world's largest economic blocs.

Its single market, industrial capabilities, international trade, and regulatory influence provide it with considerable global power.

It can establish standards, negotiate trade agreements, mobilize major financial resources, and influence the decisions of multinational corporations.

Yet economic power does not automatically translate into strategic power.

Defense requires rapid decision-making, the willingness to accept risks, operational coordination, and, under certain circumstances, the ability to employ force.

These functions demand institutions and political determination that cannot be derived simply from the size of an economic market.

For decades, the European Union compensated for this asymmetry by relying on American protection.

It could exercise substantial economic influence while leaving a decisive share of security responsibilities to NATO and, above all, to the United States.

This division of responsibilities contributed to European prosperity.

It also reduced the incentive to develop a genuinely independent strategic capacity.

Washington's changing priorities now reveal the deferred cost of that arrangement.

Europe does not lack capital, technological expertise, or a highly qualified population.

What it lacks is a sufficiently integrated capacity to transform those resources rapidly into common strategic decisions.

This distinction explains why announcements of new defense programs, however ambitious, cannot immediately resolve the problem of dependence.

Sovereignty is not measured solely by the volume of resources available.

It is measured by the ability to decide how those resources are used without depending on the authorization, assistance, or priorities of an external power.

The Transatlantic Relationship Will Not Simply Disappear

The prospect of a weakened American security guarantee should not lead to premature predictions of NATO's disappearance.

The United States retains considerable interests in Europe.

The continent remains a major commercial partner, an essential military platform, and a strategic region whose stability directly affects the international balance of power.

American installations in Europe also support operations extending beyond the continent.

They provide logistical, intelligence, and force-projection capabilities relevant to several other regions.

A complete strategic rupture would therefore impose costs on Washington itself.

Furthermore, American military institutions, NATO command structures, bilateral commitments, and industrial cooperation form an extensive network of relationships that does not disappear with every presidential transition.

The Alliance possesses an institutional depth that political declarations alone cannot erase.

It would therefore be misleading to present the future of transatlantic relations as a binary choice between unconditional protection and complete abandonment.

Several intermediate trajectories are possible.

The United States could maintain its nuclear deterrence commitments while reducing conventional deployments. European allies could assume greater operational responsibilities. American support could become more conditional, or military resources could be progressively redirected toward other regions.

Such changes could preserve NATO while profoundly altering its internal balance.

For Europeans, the challenge is to prepare for these possibilities without waiting for unilateral American decisions to determine the timetable.

Strategic Autonomy Does Not Mean Hostility Toward Washington

One of the intellectual obstacles facing Europe is the tendency to present Atlantic solidarity and strategic autonomy as mutually exclusive objectives.

This opposition is largely artificial.

Developing independent European capabilities does not necessarily mean breaking with the United States.

On the contrary, a Europe capable of assuming a greater share of its own defense could become a stronger partner, less vulnerable to changes in American domestic politics.

The real difficulty lies in how that autonomy would be organized.

A strictly national approach risks reproducing existing fragmentation.

Complete European centralization would require transfers of sovereignty that many governments are unwilling to accept.

Cooperation among smaller groups of countries could offer greater flexibility, but it would need to remain compatible with NATO structures and European institutions.

Industrial policy would be equally decisive.

Common production chains, equipment standardization, coordinated procurement, and secure access to critical materials could generate substantial efficiency gains.

However, these changes would require difficult compromises between national industrial interests.

Credible European defense would also demand the capacity to sustain prolonged high-intensity warfare.

The experience of Ukraine has demonstrated the importance of ammunition stocks, maintenance systems, logistical infrastructure, and continuous industrial production.

Technological superiority is insufficient when manufacturing capacity cannot replace equipment that has been consumed, damaged, or destroyed.

Europe must therefore recover an understanding of security in which industry, public finances, infrastructure, technology, and military readiness form parts of the same strategic system.

The Political Cost of Independence

Europe's strategic transformation will inevitably involve difficult economic and social choices.

A sustained increase in defense expenditure mobilizes resources that cannot simultaneously be allocated to other public priorities without increasing revenue, borrowing, or productive capacity.

Governments will have to balance military modernization against social protection, energy transition, infrastructure investment, and industrial competitiveness.

These decisions will become more difficult as several European economies confront modest growth, significant fiscal constraints, and increasing demographic pressures.

Yet the question cannot be reduced to competition between civilian and military expenditure.

Insecurity also carries an economic cost.

Strategic uncertainty affects investment decisions, supply chains, risk premiums, critical infrastructure, and long-term growth prospects.

A Europe unable to protect its essential interests could experience a decline in its bargaining power across fields extending far beyond defense.

Energy supply security, maritime trade routes, digital infrastructure resilience, and control over critical technologies all raise the same underlying question: to what extent can an economic power remain autonomous when it depends on other states to guarantee the basic conditions of its prosperity?

The debate over European defense is therefore also a debate about the kind of power the continent intends to become.

The End of an Era, Not Necessarily an Alliance

Transatlantic relations have experienced numerous crises.

The Suez Crisis of 1956, disagreements over the Vietnam War, tensions surrounding intermediate-range nuclear missiles, the American invasion of Iraq in 2003, and recurring trade disputes have repeatedly tested Western cohesion.

None of these crises permanently dismantled the Atlantic Alliance.

The current situation nevertheless possesses a distinctive characteristic.

It is unfolding at a time when the global balance of power is changing and the United States must distribute its resources among several major strategic theaters.

Competition with China, the war in Ukraine, instability in the Middle East, technological rivalry, and the constraints of American domestic politics make the automatic continuation of twentieth-century commitments increasingly uncertain.

For Europeans, the challenge is to recognize this transformation without succumbing to two opposing illusions.

The first would be to believe that a change of administration in Washington could permanently restore the old certainties.

American strategic priorities are evolving under the influence of structural forces that extend beyond individual presidents.

The second illusion would be to imagine that Europe could rapidly replace every function currently performed by the United States.

The dependencies accumulated over decades are too extensive to disappear within a few budgetary cycles.

Between these two illusions lies a long, expensive, and politically demanding transition.

Europe will need to preserve the benefits of transatlantic cooperation while building the capabilities required to withstand its potential weakening.

This transformation will demand more than declarations about sovereignty.

It will require industrial decisions, multi-year financial commitments, stronger military coordination, and the political capacity to define common interests.

Above all, it will force European governments to abandon the assumption that their security can be guaranteed indefinitely without their assuming primary responsibility for it.

For nearly eighty years, the American presence allowed Western Europe, and later much of the continent, to develop within an exceptional strategic environment.

That period shaped European institutions, economies, and perceptions of international relations.

It also established a deeply rooted habit: treating the American security guarantee as a permanent feature of the European order rather than as the revisable expression of another country's political choices.

It is this habit that is now approaching its end.

America is not necessarily leaving Europe.

It is reminding Europeans, sometimes abruptly, that no alliance can permanently eliminate differences between national interests.

Europe, in turn, is discovering that genuine independence does not consist of choosing between Washington and Moscow, nor of proclaiming diplomatic distance from the world's major powers.

It consists of possessing the material resources, institutions, and political determination required to decide its own future.

The American security guarantee may survive this transformation. What can no longer survive is Europe's conviction that it will never need to replace it.

Main Sources

  • NATO — The North Atlantic Treaty, April 4, 1949, particularly Article 5. https://www.nato.int/cps/en/natohq/official_texts_17120.htm
  • NATO — Defence Expenditure of NATO Countries (2014–2024), 2024 estimates. https://www.nato.int/cps/en/natohq/topics_49198.htm
  • NATO — The Hague Summit Declaration, June 25, 2025, including the commitment to invest 5% of GDP in defense and defense-related security by 2035. https://www.nato.int/
  • Council of the European Union — A Strategic Compass for Security and Defence, adopted March 2022. https://www.consilium.europa.eu/en/policies/strategic-compass/
  • European Commission — European Defence Industrial Strategy, March 5, 2024. https://defence-industry-space.ec.europa.eu/
  • Stockholm International Peace Research Institute (SIPRI) — SIPRI Military Expenditure Database, international comparative data. https://www.sipri.org/databases/milex
  • United States Department of Defense — 2022 National Defense Strategy, examining the prioritization of American strategic challenges. https://www.defense.gov/National-Defense-Strategy/