NATO Secretary-General Mark Rutte delivered a stark message to European Union lawmakers in Brussels on Monday, asserting that Europe cannot defend itself without United States military backing. He dismissed any notions of continental self-reliance as mere fantasy, urging allies to confront the harsh realities of their dependencies.

"If anyone thinks here that the European Union or Europe as a whole can defend itself without the US, keep on dreaming. You can't," Rutte declared bluntly. He emphasised the interdependence binding Europe and America, stating that both sides require each other to maintain credible deterrence in an increasingly volatile world.

This intervention comes amid simmering tensions within the 32-member NATO alliance, fuelled by US President Donald Trump's recent threats to annex Greenland. The mineral-rich territory, a semi-autonomous Danish possession and thus a NATO ally, has become a flashpoint in transatlantic relations.

Trump's rhetoric escalated in recent weeks, including proposals to impose tariffs on Greenland's European supporters. However, these threats subsided following Rutte's diplomatic intervention, which brokered a vague "framework" deal. Precious few details have surfaced about the agreement, leaving observers to speculate on its long-term ramifications for Arctic security and resource access.

At the heart of NATO's cohesion lies Article 5 of its founding Washington Treaty, which obliges members to defend any ally facing territorial aggression. This collective defence principle has underpinned European security for decades, yet Rutte's remarks highlight its fragility without American primacy.

The context for Rutte's warnings traces back to NATO's summit in The Hague last July. There, European allies—barring Spain—alongside Canada, acceded to Trump's insistence on parity in defence spending relative to US levels within a decade.

Participants committed to allocating 3.5 per cent of gross domestic product (GDP) to core defence capabilities, plus an additional 1.5 per cent for security-related infrastructure, totalling five per cent by 2035. This ambitious target reflects mounting pressure to offset perceived US burden-sharing grievances.

Rutte poured cold water on ambitions for full strategic autonomy, however. "If you really want to go it alone," he cautioned, "forget that you can ever get there with five per cent. It will be ten per cent. You have to build up your own nuclear capability. That costs billions and billions of euros."

Such a pivot would demand unprecedented fiscal and industrial overhauls across Europe. Developing indigenous nuclear forces, for instance, would rival the scale of France's existing arsenal but require coordination among fractious allies wary of proliferation risks.

France has championed the cause of European "strategic autonomy" for years, advocating reduced reliance on Washington. Support for this vision has swelled since the Trump administration signalled last year that its security focus might shift elsewhere, compelling Europeans to bolster their own defences.

Rutte countered this narrative forcefully, warning that severing ties with the US would strip Europe of its "ultimate guarantor of freedom"—the American nuclear umbrella. "So, hey, good luck!" he quipped, underscoring the existential stakes.

These exchanges expose deeper fissures in NATO's unity. Trump's Greenland gambit, though partially diffused, underscores his unpredictable approach to alliances, blending economic leverage with security imperatives in the resource-scarce Arctic.

For Denmark, the episode represents a sovereignty test, with Greenland's rare earth minerals vital for green energy transitions and defence technologies. Any US foothold could reshape NATO's northern flank, potentially drawing in Russia or China.

European defence spending has risen since Russia's 2022 invasion of Ukraine, yet gaps persist. Many allies still fall short of the longstanding two per cent GDP benchmark, let alone the five per cent pledge. Rutte's intervention serves as a rallying cry to accelerate investments in air defence, cyber resilience, and munitions stockpiles.

Looking ahead, Rutte's words challenge proponents of EU-led defence integration, such as the European Defence Fund. While initiatives like permanent structured cooperation (PESCO) show promise, they lack the scale to supplant US contributions in conventional or nuclear domains.

Trump's return to the White House amplifies these dilemmas. His administration's "America First" ethos demands tangible reciprocity, potentially conditioning US commitments on European concessions—from trade to basing rights.

As geopolitical pressures mount—from Indo-Pacific tensions to Middle Eastern instability—NATO's European pillar must evolve without fracturing. Rutte's realism may galvanise action, but it also risks alienating autonomy advocates in Paris and beyond.

The Secretary-General's address reframes the debate: Europe's security is not a solo endeavour but a shared transatlantic imperative. Failure to heed this could invite adversaries to exploit divisions, testing the alliance's endurance in an era of renewed great-power rivalry.