This week marks a watershed moment in transatlantic relations and the ongoing war in Ukraine, triggered by a seismic shift in U.S. policy under President Donald Trump and a consequential European response spearheaded by European Commission President Ursula von der Leyen.

Trump’s decision to freeze military aid to Ukraine, announced mere days ago, intensifies tensions between Washington and Kyiv at a critical juncture. The move follows a high-stakes Oval Office meeting last Friday between Trump and Ukrainian President Volodymyr Zelensky, which ended in a diplomatic impasse.

Reports suggest that Trump, alongside Vice President J.D. Vance, conveyed frustration over what they perceived as Zelensky’s lack of appreciation for past U.S. support. The administration appears intent on strong-arming Ukraine into negotiations with Russia, potentially compelling Kyiv to cede territory in pursuit of an uneasy peace—a stance emblematic of the broader skepticism within Trump’s camp regarding America’s global military entanglements, particularly in Ukraine.

This pivot in U.S. policy raises profound concerns. For decades, U.S. leadership has served as the bedrock of a rules-based international order, where backing allies like Ukraine has functioned as a deterrent against authoritarian expansionism—especially from Vladimir Putin’s Russia. Trump’s abrupt withdrawal of aid undermines Ukraine’s defensive capabilities at a precarious moment, signaling to Moscow that the U.S. is retreating from its historic role as Europe’s security guarantor. The pause in military assistance, valued in the billions, threatens to erode Ukraine’s battlefield resilience, even though Kyiv has weathered previous disruptions in aid.

Europe, however, is not waiting idly. In direct response to Trump’s decision, von der Leyen unveiled an audacious “ReArm Europe” initiative on March 4—an expansive $840 billion blueprint designed to fortify Europe’s defense infrastructure and counterbalance Washington’s growing reluctance. She is set to present the proposal at an emergency EU summit on March 6, underscoring the pressing need for Europe to assume greater responsibility for its security in the wake of Trump’s mounting hostility toward NATO and his questioning of long-standing alliances.

The “ReArm Europe” plan is structured around three core imperatives. First, von der Leyen proposes that EU member states increase defense expenditures by an average of 1.5% of GDP without triggering the bloc’s restrictive deficit constraints—potentially unlocking $700 billion over four years. A supplementary $162 billion common defense fund would provide low-interest loans to spur military investments. Second, the initiative prioritizes expediting immediate military assistance to Ukraine, with a focus on bolstering air and missile defense systems, artillery, drones, and anti-drone technology—capabilities that are pivotal to Ukraine’s survival. Finally, by harnessing the EU budget and mobilizing private capital, the plan seeks to streamline joint procurement, drive down costs, and strengthen Europe’s defense industrial base, thereby advancing strategic autonomy.

Von der Leyen framed her initiative as “Europe’s moment,” accentuating the imperative for the continent to shoulder greater responsibility for its defense and that of its neighboring allies. “We are in an era of rearmament,” she declared, signaling Europe’s urgent response to both Russian aggression and the unpredictability of American foreign policy. Her strategy aligns with the liberal tenets of multilateralism and collective security, yet it simultaneously exposes the accelerating scramble within Europe to mitigate the consequences of Washington’s growing disengagement.

Trump’s deep-seated skepticism of NATO and his repeated demands that European nations “pay up” for U.S. military protection have exacerbated transatlantic divisions. This week’s developments hint at the potential unraveling of the post-World War II alliance structure that has underpinned Western stability for decades. The upcoming EU summit will not only serve as a forum to evaluate von der Leyen’s plan but also as a crucial moment to strategize ways to sustain Ukraine in the absence of U.S. support. European heavyweights, including German Foreign Minister Annalena Baerbock and incoming Chancellor Friedrich Merz, have amplified von der Leyen’s call for an autonomous European defense posture—an idea rapidly gaining traction across the continent.

For Ukraine, the stakes have never been higher. Zelensky’s failed negotiations with Trump have left Kyiv confronting a U.S. administration that appears willing to subordinate Ukrainian interests to a hastily brokered settlement with Russia. Trump’s advisors have even floated the notion of leveraging Ukraine’s vast mineral resources to retroactively “offset” previous U.S. aid—a proposition laden with economic and geopolitical complexities. Meanwhile, Moscow is undoubtedly observing these developments with keen interest, sensing an opportunity to exploit Western disunity. The EU’s pledge to ramp up aid provides Kyiv with a crucial lifeline, but whether Europe can fully compensate for the loss of American military backing remains an open question.

This week’s events serve as a sobering warning: America is stepping back, Europe is stepping forward, and Ukraine is left precariously positioned as Russia looms. Supporting Ukraine transcends the immediate crisis—it is about upholding the foundational principle that national borders cannot be redrawn by force, a cornerstone of international law. Trump’s transactional approach risks emboldening autocrats like Putin, dismantling decades of American efforts to foster democracy and stability in Europe. While von der Leyen’s response is both bold and necessary, it also underscores the fragility of a transatlantic partnership increasingly tested by America’s inward turn.

The EU’s $840 billion plan is a monumental step toward European defense self-sufficiency, yet formidable challenges loom. Political resistance from fiscally conservative member states, logistical obstacles in scaling up defense production, and internal EU discord—especially from Hungary’s Viktor Orban, who has previously obstructed Ukraine aid packages—could impede its execution. The liberal hope is that Europe will rise to the occasion, preserving the transatlantic alliance’s foundational principles even as Washington wavers. But the overarching question remains: can Europe and Ukraine sustain their resistance against Russian aggression without the full backing of the United States?

This is an inflection point. The geopolitical landscape is shifting, and the choices made this week will have profound ramifications for years to come.