At its 2026 summit in Ankara, the NATO alliance survived another close encounter with U.S. President Donald Trump and declared in its communiqué “a stronger Europe in a stronger NATO.” The organization also reconfirmed all allies’ commitment to its Article 5 collective-defense clause. But the summit did not tackle, let alone resolve, the alliance’s fundamental problem.

That problem is not just about transatlantic burden sharing or European defense spending, important though these things are. It is that European governments can no longer confidently explain how Europe’s collective defense will be ensured. The problem is not just that Trump might not come to Europe’s defense in a major hybrid or high-intensity conflict with Russia but, more profoundly, that modern America might be increasingly unlikely to do so in the future. Europe’s trust in the reliability of the United States as its key security provider has been shattered.

Europe’s collective defense will survive as a transatlantic project only if Europe and the United States can rebuild trust around a new, credibly long-term, common vision of the two sides’ respective roles. Europeans must now take the initiative on the design and construction of that vision.

The European trio (E3) of Paris, Berlin, and London—ideally with other partners, such as Rome and Warsaw—can and should lead this initiative. A politically feasible soft vision is readily available: Europe should progressively take primary responsibility for its own defense. But governments should also consider a strong, politically bolder, and, arguably, more credible vision: For Europe’s collective defense, European capabilities should gradually become separable, but not separate, within the NATO framework in case the United States is not willing or able to engage in a European conflict.

Brussels, We Have a Problem

European leaders can hope that things will get better after Trump leaves office in 2029. But the U.S. turn away from alliances is a long-term trend. U.S. domestic political polarization is set to make the United States a much less reliable partner for decades to come. The Ankara summit may have done enough to keep Moscow deterred for the time being, although Russian hybrid attacks and verbal threats are escalating and increasing the risk of the war in Ukraine getting out of hand. But despite Trump’s declaration of the “tremendous love” he felt from other NATO leaders and the communiqué’s ritual recommitment to the defense of all allies, the summit did nothing to ease Europeans’ private doubts about whether the United States will be there for them when the chips are down.

Europe’s security is at stake. It is for European governments to develop a vision for restoring the credibility of Europe’s collective defense. This vision must be transatlantic, because for many years to come, Europe will depend on the United States’ critical enablers and extended nuclear deterrence. A strong commitment to greater European military and security capabilities and a plan to get there are prerequisites for such a vision. But at the heart of any credible, Europe-owned vision is the governance question: How will the preparation for and conduct of collective defense and deterrence be progressively de-risked from a possible U.S. lack of will or capability to engage in a major European conflict?

The NATO formula of moving toward a more European NATO points in the right direction, but it ducks this core governance question. It is easy to sympathize with NATO officials and governments for wanting to kick the can into the next U.S. administration for fear of provoking counterproductive reactions from the present one. What is more, good work is being quietly done at NATO through successive four-year cycles of the confidential NATO Defense Planning Process to reduce European dependence on the United States. The alliance is addressing the financial dimension through all allies’ commitment to increase their military and security spending to the equivalent of 5 percent of national GDP by 2035. NATO is wrestling with defense-industrial questions about how to overcome the fragmentation of European production and procurement and sustain European capacity. And the alliance has broached the delicate subject of European nuclear deterrence, as shown by the July 2025 British-French Northwood Declaration on nuclear cooperation and French President Emmanuel Macron’s March 2026 offer of a nuclear dialogue with allies.

Good work is being quietly done at NATO through successive four-year cycles of the confidential NATO Defense Planning Process to reduce European dependence on the United States.

But confidential technical planning and piecemeal policy debates are not the political project that Europe and the transatlantic relationship need to tackle the governance question. European leaders must provide a stronger sense of direction and European ownership if European publics are to be mobilized for the long haul and U.S. decisionmakers are to be persuaded to remain engaged. It is unhealthy for politics on both sides of the Atlantic if all the proposals for Europe’s security come from Washington. Difficult though the question of de-risking from the United States is, not tackling that question is even more corrosive for Europe’s self-confidence and transatlantic respect.

More European leadership is therefore not just necessary but prudent and urgent. Prudent because the present U.S. administration is at least as likely as any successor to respond positively to European allies taking the initiative. Urgent because working toward the 5 percent spending target and invisible planning for burden sharing in NATO are not enough to keep Europe’s collective defense politically credible when the transatlantic bond is so uncertain.

Autonomous European Collective Defense

Further disorder inside NATO—including more punitive U.S. troop adjustments of the kind seen since the start of the war on Iran and cancellations of missile deployments, not to mention U.S. threats against allies—could make it imperative for credible deterrence that Europeans transition to collective defense outside the alliance.

Alternatively, a future U.S. administration could be even more isolationist than Trump’s. It could wish Europe every success in its long game with Russia and still want the Europeans to look after their own security and to do so outside NATO. That is not where the U.S. Congress or electorate is today, and it is highly unlikely that the United States will leave NATO anytime soon. But who can predict where the country will be in the 2030s?

Either way, any disengagement or separation could be amicable. Trade, geopolitical cooperation, intelligence relationships, and people-to-people contacts might all flourish. Both sides of the Atlantic would have a strong interest in ensuring that their military and security arrangements remained. At least for a transitional period, Europe would need to negotiate continued access to crucial U.S. capabilities.

All that said, when it comes to achieving autonomous European collective defense, three possible approaches are conceivable.

A Coalition of the Willing

Already with both Ukraine and the Strait of Hormuz, Europeans have had to do their collective military planning outside NATO. That requirement has shown that at least on some geostrategic issues, coalitions of the willing can function and leadership can be found. Indeed, there is a growing sense of NATO minus one.

There are also prefabricated European defense coalitions around which collective-defense arrangements could theoretically be built, such as the Joint Expeditionary Force initiated by the UK and consisting of ten mostly Nordic and Baltic countries. But coalitions of the willing, even premade ones, are far less satisfactory for the sustained, life-or-death collective defense of Europe than for one-off, time-limited tasks.

Deterring Russia requires standing forces, all of which are currently dedicated to NATO. European nuclear deterrents must also be integrated with conventional capabilities, and Europe needs a substantial, continuous military planning capability. All these requirements would have to be confronted in any purely European set of arrangements, as would the short- and medium-term lack of the critical enablers that are currently provided by the United States through NATO. The particular problem with a coalition of the willing is one of governance: Participation in collective defense cannot be ad hoc, and command-and-control arrangements must be settled, agreed on, and exercised. In short, there needs to be more of an institutional structure than any coalition options would provide.

EU Collective Defense

This institutional requirement typically leads EU commentators to propose that if Europe’s collective defense were to be done without the United States, it should be done within the EU framework.

On the one hand, this might indeed be a long-term solution. The EU has political energy and a raison d’être. It already has a treaty-based collective-defense provision. Bringing collective defense into the EU would bring defense closer in line with the union’s finances and regulatory power than current EU-NATO coordination can; this could include more efficient defense procurement in a future EU defense union. Such a move would have legitimacy in the form of oversight by the European Parliament. And it could build on existing EU decisionmaking and command-and-control practices.

On the other hand, the EU has yet to build a strategic security and defense culture—a problem for any non-NATO arrangement. What is more, several EU members are neutral countries or support the Treaty on the Prohibition of Nuclear Weapons. Partly as a result, the union as a whole might find it politically difficult to embrace the nuclear dimension of deterrence.

And a purely EU solution would exclude some significant European military powers from core decisionmaking on collective defense. Especially in circumstances in which the Europeans could not assume to have the United States’ sympathy, let alone its support, it would make sense to include nuclear Britain, frontline Norway, and capable and strategic Turkey.

A European Defense Union

These governance difficulties have contributed to proposals for a full-fledged, self-sustained European Defense Union. For instance, European Commissioner for Defence and Space Andrius Kubilius has called for a European Security Council of permanent and rotating elected members; the council could, if necessary, lead on to a European Defense Union that might have decisionmaking powers over war and peace. The proposition itself is not new, having been launched by France and Germany in 2017. But it was rekindled by the president of the European Commission in her 2026 State of the Union address.

The idea behind this proposal is that existing EU decisionmaking is slowing the EU’s conversion into a military power and would be inadequate in a serious crisis. The council’s recommendations could accelerate the EU’s defense reform in the near term, and in time it could become a decisionmaking body able to exert political control over major European military operations.

The council could, if necessary, lead on to a European Defense Union that might have decisionmaking powers over war and peace.

This is a serious proposal to address some of the obvious governance fault lines in any non-NATO arrangements. But it presents its own difficulties. Instead of allowing leadership to emerge ad hoc, it would force a negotiation of which countries have permanent status and which do not. That negotiation might take as long as negotiating a European Defense Union itself. In addition, any EU treaty changes would be a lengthy and high-risk enterprise, given the uncertain politics of many EU members.

A More European NATO

The challenges of constructing a non-NATO European defense pillar, coupled with Europe’s strategic interest in keeping the United States engaged in Europe’s collective defense for as long as possible, should lead Europeans to focus on NATO solutions.

Both practically and politically, a transatlantic rebalancing within the NATO framework is more likely to deliver the transition, not rupture, that European defense needs. On the specific matter of collective defense and deterrence, NATO is institutionally better equipped than anything outside the alliance. This is especially true as long as the United States is prepared to support collective defense from inside NATO. It is true not only because Europe’s collective defense needs U.S. capabilities for a long time to come but also because a Europe-U.S. alliance still makes geopolitical sense.

This is not to suggest that Europeans should abandon efforts outside NATO relevant to their collective defense. On the contrary, goals such as a more efficient European defense industry, more efficient European defense procurement, the development of a stronger European nuclear deterrence, and more effective NATO-EU collaboration should ideally all feature in any European initiative.

However, the 2026 U.S. National Defense Strategy’s proposal that Europe take “primary responsibility” for the conventional military dimensions of NATO’s collective defense raises many governance questions. For Europeans, after a shift to European primary responsibility, will it work politically for the United States to continue to have the leading voice in the North Atlantic Council it is accustomed to? If Washington will not cede a stronger role to non-U.S. allies, where and how can Europeans shape their own positions and have the necessary voice to defend their primary responsibility?

Another basic issue may be nuclear. The U.S. National Defense Strategy confirms that the United States will continue to provide its critical nuclear umbrella to allies to deter Russia and complement a more European NATO conventional defense. But it is far from clear whether, under this administration, the United States will have Europe’s back to the extent of putting the U.S. homeland at risk. So, does the rebalancing go far enough, or should “more European” extend to NATO’s nuclear arrangements and not just its conventional ones? On the other side of the coin, for Washington, would it be politically tenable to continue to provide Europeans with a nuclear umbrella if they get into a conflict with Russia and the use of nuclear weapons becomes an actual issue?

It is far from clear whether, under this administration, the United States will have Europe’s back to the extent of putting the U.S. homeland at risk.

Europeans will have earned the answers to such questions only once they have greatly strengthened their military capabilities. That will require strong political resolve and a sustained financial effort from all Europeans over many years. But the questions are nonetheless politically and strategically vital today. The fundamental issue is whether the rebalancing of NATO to European primary responsibility will be done with or without full U.S. support. A rebalanced NATO born of constant U.S.-Europe confrontation is a recipe for disaster. The U.S. National Defense Strategy implies full support for such a shift. The current consultation process within NATO, launched by the United States and framed as an effort to build a NATO 3.0, seems to lean in that direction. Yet, MAGA politics suggest otherwise.

Toward European Primary Responsibility

A core group of European countries would be well suited to initiate the necessary debate on how to shape the governance of a more European NATO. This group should start with the E3: the EU nuclear power, France; the largest European defense power, Germany; and the other European nuclear power, the UK. If Poland, as the militarily strongest frontline state; Italy, with its important industrial base and geostrategic position; and other nations like Finland or Sweden could be persuaded to join such an initiative, so much the better.

At the heart of this plan should be a publicly explicable process to get Europe to primary responsibility for the whole of the continent’s future collective defense. Leaders could build on the 5 percent spending commitment and say that acquiring the necessary capabilities will enable Europe to take primary responsibility for its collective defense no later than 2035.

What such responsibility actually means—and how this goal is to be implemented—would then be hammered out over the following years in full collaboration with the United States through NATO’s Military Committee and the North Atlantic Council. But at least the political direction of travel would have been unambiguously set.

Such a process would ideally come with target dates for achieving given capabilities and specific planning. It would get ahead of U.S. demands and expectations by putting European allies on the front foot politically. It would appeal to a wide swath of European opinion, including nationalist governments. Joint U.S.-European military planning could cater for more European ways of war and, at the same time, work out how to remain interoperable with the United States.

This plan should also indicate the next steps toward Europe’s deterrence of nuclear Russia and set out how NATO can best work with Macron’s nuclear overture to European allies. As a Europe-driven initiative, it would ensure the European voice that many want, without creating a potentially divisive European caucus inside NATO—in short, a managed transition rather than another rupture. The plan’s level of ambition would be a key driver of greater European effectiveness across the supporting defense enterprise.

Objectors may say that such a process would create a self-fulfilling prophecy of accelerating transatlantic separation. But that is surely a smaller risk and a more promising alternative than living with the bad consequences of increasing U.S. resentment at the United States’ overexposure in Europe. Critics might also argue that such an initiative would shine an unwelcome spotlight on European nuclear deterrence. But Trump has ensured that the spotlight is already there.

Any process toward European primary responsibility will inevitably have to address how and to what extent Europe will acquire capabilities enabling it to cope, if necessary, without the equivalent U.S. capabilities in a collective-defense crisis. For Europeans, the answer to this question will turn on how far they think the United States could be relied on to either deliver a given capability or let Europeans acquire it on their own. For Americans, it will turn on how reliable they want to be and which capabilities they want to contribute to Europe’s collective defense in the long run.

The judgments to be made across a wide range of capabilities are on a sliding scale, with no simple answers. Clearly, both sides of the Atlantic are stronger and more secure together than apart. Even if Europeans were to reach an eventual point at which they could deter on their own, their deterrence would be more robust if the United States were politically and militarily in the mix. Judgments about the capabilities and plans in which Europe should be self-sufficient might vary over the years, and the transatlantic debate could be iterative.

Separable, Not Separate, Capabilities

There is a geopolitical case for a bolder approach than just full European primary responsibility. Given the present state of transatlantic relations, Europeans need to know that in principle, if they work hard at capabilities in the years to come, they could conduct their collective defense on their own if required. America, too, needs to know that if it is distracted or facing a major crisis outside Europe, its European allies could cope on their own. Politically, both sides of the Atlantic are more likely to stay together in NATO for the long haul if they feel less shackled to each other.

A more ambitious step could be added to full European primary responsibility. It is worth exploring an old idea that would set a clear political direction: Berlin Plus. The concept derived from NATO’s 1999 decision to allow the EU to access NATO assets. Berlin Plus was formally launched in 2003 and enables the EU to use separable—not separate—NATO military planning, logistics, and forces for the union’s own peacekeeping or crisis management operations if the United States chooses not to be involved in a European conflict.

Europeans need to know that in principle, if they work hard at capabilities in the years to come, they could conduct their collective defense on their own if required.

Governance within NATO on the basis of this principle could be presented as a new NATO Berlin Plus, in which the long-term goal is that separable allied European—not only EU—capabilities inside NATO can be used in crises or conflicts in which the United States does not wish to be involved.

Alarmed officials expressed in interviews their concern that such an arrangement could mark the end of NATO. Not necessarily. It is certainly true that U.S. nonparticipation in a major high-intensity war in Europe following an armed attack on one or several allies would mean the end of NATO as we know it. But a full NATO Berlin Plus arrangement would enable Europeans to act through NATO rather than outside, if the United States decided not to be involved. If separable European capabilities were developed inside NATO, European allies would have at their disposal not only NATO’s planning, standards, and interoperability but also the alliance’s collective-defense mechanisms and decisionmaking structures.

That will not happen anytime soon. But starting to work on such an arrangement would immediately concentrate minds in both Washington and Europe on how a separable European collective defense would be led. As an extended process, it would create time and space to work out the governance. It could be the essential new transatlantic bargain that gives both sides of the Atlantic what they want.

Political decisionmaking in a NATO Berlin Plus situation would require a watertight agreement with the Americans that they would not block European decisions if they did not want to be involved. What is more, decisionmaking in this format would still be based on European unanimity. But no European nation can play the old U.S. role of a benevolent hegemon that brings Europeans together. A more European NATO would revive the highly sensitive question of leadership in Europe in a rather fundamental way. However, Europeans have shown themselves well able to develop organic, sensible, realistic leadership solutions. They have done so successfully with recent coalitions of the willing. There is no reason to conclude they would be unable to manage in a rebalanced NATO.

There is no easy answer to the problem of European security, as it has not only wide-ranging military and financial but also political implications. Yet, among all the difficult options, a more European NATO seems to be the best to secure Europe’s future collective defense. It is time for European nations to give this option conceptual substance and political momentum. What is missing today is a clear European sense of purpose and genuine political will to lead the way.