By Eric Vandenbroeck and co-workers

Europe’s War in Ukraine

Relations between the United States and its European allies have proved tempestuous during the first two months of the second Trump administration. From his first days back in office, President Donald Trump has emphasized significant disagreements with the European Union, characterizing the bloc as inimical to U.S. interests, while Vice President JD Vance argued at the Munich Security Conference in February that the values of the United States and Europe are diverging. Between the stated ambition of the administration to annex Greenland and the imposition of wide-ranging tariffs, European leaders are bracing for a challenging transatlantic relationship.

The tenor of European concerns, however, changed markedly as the Trump administration began to make its opening forays into an attempt to end Russia’s full-scale invasion of Ukraine. Following a public confrontation with Ukrainian President Volodymyr Zelensky in the White House in February, Trump temporarily stopped providing Ukraine with military-technical assistance and intelligence, coercing Ukraine into accepting a negotiating strategy that excluded Kyiv and its European partners from much of the direct bargaining with Moscow. Despite Russian President Vladimir Putin rebuffing a U.S. proposed cease-fire, Trump has described his interactions with the Kremlin in the most positive of terms, while so far, applying U.S. leverage against only Kyiv. The administration, meanwhile, has been unequivocal that there will be no long-term U.S. commitment to Ukraine and has called into question whether U.S. commitments in Europe will be honored.

As the diplomacy lurches forward uncertainly, the battlefield situation in Ukraine continues to deteriorate. Russian forces have largely pushed Ukrainian forces out of Kursk oblast—territory in Russia that Ukraine had occupied since August 2024—and are now restarting major offensive operations toward the key Ukrainian towns of Kostiantynivka and Pokrovsk. Although the Ukrainian military is ensuring that Russia loses many soldiers and much equipment in making these territorial gains, the Ukrainians are also struggling to recruit and train enough personnel to avoid ceding territory. Both countries, meanwhile, are exchanging nightly long-range strikes targeting infrastructure and military logistics.

The risk that the United States may once again sever support has led Kyiv to explore how it can sustain its resistance—and thereby maintain leverage in negotiations—through European assistance alone. Trump has forced Europe to plan on underwriting its own and Ukraine’s security, both for the duration of the war and the peace that follows. The immediate question is whether this is possible. The short answer is both yes and no. Europe has the latent capacity to produce much of the materiel that Ukraine requires to fend off Russia, but it has not prepared effectively to shoulder this burden. It can replace the United States as Ukraine’s primary security provider, but doing so will take time, require difficult collaboration, and be costly. Although those hurdles are real, they are not insurmountable. Embarking upon this undertaking, however, is likely to transform Europe’s relations with the United States.

 

A Predictable Surprise

Europe should have seen this coming. Going back to the Obama administration, the United States has been consistent in acknowledging that it views its primary security competitor as China. Washington’s growing interest in the Indo-Pacific has meant that successive U.S. administrations have wanted to deprioritize the U.S. commitment to Europe. For that to happen, the Americans have urged European countries to build up their armed forces to ensure conventional deterrence against Russia—and thereby free up American capacity to pivot to Asia.

Up until the second Trump administration, those American demands had been functionally ignored. Although there was some symbolic investment into defense after Russia’s annexation of Crimea in 2014 and an increase of around 30 percent in European defense spending between 2021 and 2024, Europe has not so far resourced its militaries to a level where they can perform their functions in relation to NATO plans. Even the full-scale invasion of Ukraine in 2022, while prompting a great deal of tough rhetoric in Europe, did not push governments to make the necessary investments to regenerate their hollow forces. European leaders were reluctant to bear the cost of this process and feared that a large increase in European defense spending would accelerate the United States’ withdrawal from the continent, making the burden for Europeans permanent.

Hiding from a Russian combat drone in Pokrovsk, Ukraine, March 2025

Europe bears significant blame for not doing more to address U.S. concerns prior to Trump regaining office. But the manner in which Trump has forced the issue has prompted a particularly visceral response in European capitals. Trump could have told NATO members that he would not honor Article 5—the article in the alliance’s charter that insists that an attack on one NATO country is an attack on all—for states that failed to meet their NATO commitments, which would have required around three percent of GDP in defense spending from most members. Such an ultimatum would likely have rankled European capitals, but many would have complied. The United States, after all, would have been simply demanding that these states front the funds for what they had promised to do. Instead, the administration’s withdrawal of support for Ukraine cut much deeper. It risked a rapid deterioration in European security by giving Russia a path to achieving a range of its hostile designs on Ukraine, and it left both European leaders and publics feeling betrayed. European countries no longer trust that the United States will protect their interests, even in the most fundamental areas of security and defense.

The United States now faces an important choice. If it supports and enables the regeneration of Europe’s defense industrial base and does not obstruct Europe’s support for Ukraine, then the United States could achieve its objective of helping Europe manage its own defense and security, allowing Washington to fulfil its long-standing goal of redistributing forces to the Indo-Pacific. But for decades, U.S. defense industrial policy toward Europe has instead aimed at balkanizing and undermining Europe’s own defense industry to encourage U.S. foreign military sales on the continent. The United States has also expected to lead the alliance because its involvement has been necessary for almost any serious military undertaking.

If the United States tries to force a process of European rearmament by compelling European countries to buy more U.S.-made weapons, it will not be successful. Of course, Europe is unable to produce some kinds of critical weapons systems, such as the Patriot air defense system, and will continue to rely on purchases from the United States. But with their publics already distrustful of Washington, European governments will balk at the pressure to buy American. And Europe’s dependence upon the U.S. defense industrial base will not provide a strong foundation for medium- and long-term support to Ukraine or to deter Russia, given the likelihood that the United States will eventually need to divert industrial capacity to address the balance of forces in the Pacific. If the United States uses export controls to try to prevent European manufacturing domestically (many supply chains for microelectronics and components in complex weapons span the Atlantic), then Europe will likely diverge faster from the United States, even at the cost of being armed with less capable weaponry.

 

An Orderly Transition?

How the United States chooses to shift the burdens of the war onto Europe will shape what the Europeans can accomplish. Much depends on whether the United States wants Ukraine to be able to continue to defend itself as it negotiates or whether Washington is prepared to force Kyiv to settle on any terms.

With good reason, many European governments fear that the Trump administration is fundamentally ambivalent about the course of the war. A Ukrainian defeat or a cease-fire on terms heavily favorable to Russia would force Europe to rearm, which is, after all, a U.S. strategic objective. The United States could negotiate a deal with Russia and then steadily ratchet up pressure on Ukraine until it agrees to the deal’s strictures. Indeed, the United States could try to force Ukraine—and by extension Europe—to comply.

Washington could, for instance, turn off Kyiv’s Starlink terminals, the satellite communications technology. Starlink has proved essential to the Ukrainian war effort. Its cessation would cause an immediate breakdown in command and control across Ukrainian frontlines, which would be militarily disastrous. Given the scale of Ukraine’s reliance on Starlink, European countries would not be able to quickly compensate for a sudden withdrawal of service in the short term. Starlink is not irreplaceable, and an alternative command-and-control infrastructure can be built. But Ukraine’s current dependence on this system leaves it very exposed.

The United States has tremendous leverage over Ukraine and its European allies when it comes to servicing existing stocks of weapons and equipment. In addition to the military equipment the United States has provided Ukraine, much of the equipment and weapons sent by other Ukrainian partners was also purchased from U.S. defense companies. These include M777 and M109 howitzers, Abrams Main Battle Tanks, Bradley Infantry Fighting Vehicles, High Mobility Artillery Rocket Systems (HIMARS) and M270 multiple-launch rocket systems, F-16 fighter aircraft, and various kinds of armored personnel carriers. It is one thing for the United States to insist that it will not spend on new equipment for Ukraine, but quite another for it to stop maintaining or providing spare parts for equipment already in use. The United States could also forbid European states from purchasing the relevant spare parts and then sending them to Ukraine. Ukraine’s armed forces currently have approximately 4,000 pieces of military equipment awaiting repair, and more are damaged every day in combat. Europe, over time, can transition Ukraine’s military to systems it can support without U.S. help. But if the United States moves aggressively to prevent the maintenance of equipment already given, then Europe will be powerless to arrest the steady demechanization of the Ukrainian military.

As the leading member of the alliance, the United States has provided the bulk of the logistical support, transportation capabilities, and personnel for running military-technical assistance to Ukraine. As in other areas, Europe could not replace this assistance swiftly. The EU can manage logistics at scale within its borders, and European countries have significant assets and capacity to plan and execute operations. But most of the structures for planning and executing military logistics in Europe sit within NATO and have substantial U.S. involvement. Washington could have its staff in the United States European Command gradually transfer control of logistics to European counterparts. But if Washington blocked its staff from assisting such a handover, then Europe would need to replicate the existing structures rather than replace U.S. personnel in NATO posts. This would significantly complicate the process.

Ukrainian forces in the Zaporizhzhia region of Ukraine, March 2025

 

Continental Coherence

Another major impediment to Europe taking the reins from the United States is the continent’s lack of cohesion. Take, for instance, the European defense industry. Although European defense companies have the relevant expertise to produce most classes of equipment necessary to sustain Ukraine’s war effort, almost all European countries procure too few of these platforms to ensure a meaningful return on investment for those companies without selling at an inflated cost. With no expectation of receiving big orders, European manufacturers tend to have small facilities and face hostile regulation when it comes to expansion. Addressing this challenge requires continental collaboration to expand the size of orders at each step in the supply chain and reassure firms that they’ll get a good return on investment if they enlarge their facilities and capacities.

Although the European Union’s financial clout and regulatory support will be essential to expanding Europe’s defense industrial base, EU member states will need to work with the United Kingdom, Norway, and Ukraine itself, without letting discussions get derailed by non-defense-related issues. Diplomats will have to compartmentalize lingering disputes. Parochial spats between France and the United Kingdom about fisheries, for instance, or between Poland and Ukraine about agriculture should not be allowed to scupper the process.

NATO is also a source of tension. Investment in Europe’s defense industrial base would significantly strengthen NATO’s resilience and ability to sustain large-scale combat operations, but continuing to give more equipment and stores to Ukraine will come at the expense of European readiness to execute NATO’s plans for the defense of the Euro-Atlantic area. For countries bordering Russia, this is a very uncomfortable situation. Moreover, Hungary and others could act as spoilers and block pragmatic solutions within the EU. To maintain European cohesion, therefore, European governments will need to collectively recognize that some countries will face immediate risks for which they have greater defense needs than others, and so the task of supporting Ukraine should fall disproportionately on Western European states.

Only if Europe can rationalize supply chains across the continent and achieve economies of scale in defense production will it have the capacity to meet Ukraine’s needs. Under the current system, in which countries compete with one another for parts and supplies—thereby driving up the prices of defense materiel—Europe will fail. Consider artillery ammunition. In 2023, Ukraine received approximately 1.6 million 155mm artillery rounds from its international partners, including the United States. In 2024, Ukraine received approximately 1.5 million rounds. Analysts believe Ukraine needs 2.4 million rounds per year to prevent further Russian advances. That disparity seems to suggest that without U.S. supply, Europe cannot sufficiently back Ukraine.

But Europe is not using its capacity as well as it could. In the United Kingdom, for instance, the actual forging and filling capacity for 155mm shells is 16 times greater than at the start of Russia’s full-scale invasion. Despite this increase in capacity, there has been no concurrent increase in production as the United Kingdom has not placed the orders. That is in part because Europedoes not produce enough explosives, so that although manufacturers can make the shells, they struggle to source propellent charges for them. Another British defense firm, however, has been trying to significantly expand its explosive-powder plant since 2022, only to have its proposals turned down multiple times by a local council. Central government has done nothing to pressure the council to abandon its parochialism. If permission were granted, propellent production could grow in a matter of months. The picture is quite similar across the continent. Europe may not be able to get to 2.4 million rounds in 2025, but with greater coordination and determination, it could replace U.S. contributions by the end of the year.

Europe will seriously struggle to meet Ukraine’s needs in several areas. It can do very little to replace the U.S.-made interceptors used in Ukraine’s Patriot air defense batteries, the only system able to intercept Russian aeroballistic and quasi-ballistic missiles. Most of the damage Russia inflicts on Ukraine, however, is caused by cruise missiles that can be intercepted with European arms, such as SAMP/T and IRIS-T missiles, and most Russian ballistic missile strikes are against targets that are not defended by Patriots. With European backing, Ukraine could find ways to minimize the impact of Russia’s relatively few ballistic missile strikes and, in turn, target the supply chains that undergird the production of Russian ballistic missiles. In short, even where Europe cannot compensate for the United States, the consequences need not be catastrophic.

 

No Excuses

The fundamental question underpinning Europe’s ability to shoulder the burden of its security—beyond the extent to which this effort is actively obstructed by U.S. policy—is will. As already mentioned, funding existing European commitments to NATO would have brought spending above three percent of GDP for most members. Achieving a rapid expansion of defense industrial capability to sustain Ukraine in addition to regenerating military forces would see the cost grow even higher. So far, European states have been reluctant to commit resources. Germany has just announced an increase in defense spending, while the EU more broadly has shifted its debt rules to allow more borrowing for investment in defense. But as with German announcements in 2022, it is not yet clear that these statements will drive an effective process of rearmament. It is up to the Europeans to determine whether they can stomach the cost, but they should not hide behind the claim that they cannot defend Ukraine without the United States. Much depends, however, on whether the United States wants that transition to take place.

 

 

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