In an exclusive interview with The Telegraph published on 1 April, US President Donald Trump described NATO as a "paper tiger" and stated that American withdrawal from the alliance was "beyond reconsideration." The interview came against the backdrop of allied refusal to support the US–Israeli air campaign against Iran, launched on 28 February, and specifically to help reopen the Strait of Hormuz, which Tehran has effectively blockaded for weeks.
Trump singled out the United Kingdom for rebuke, mocking the state of the Royal Navy and dismissing Prime Minister Keir Starmer's priorities. Secretary of State Marco Rubio, speaking hours before the interview aired, called NATO a "one-way street" and confirmed that a formal re-examination of US membership would follow the conclusion of hostilities. Administration sources also floated a "pay-to-play" model that could strip non-compliant allies of decision-making power, alongside renewed consideration of withdrawing US forces from Germany.
The interview amounts to the most explicit threat of American disengagement from the Atlantic alliance since its founding in 1949. Even if the rhetoric is partly designed to coerce concessions, the strategic signalling is unmistakable — and nowhere are its implications felt more acutely than on NATO's southeastern flank.
The Southeastern Flank: A Unique Vulnerability
The southeastern periphery of the alliance — anchored by Greece and Turkey, flanking the Aegean, the Eastern Mediterranean, and the Black Sea approaches — has always occupied an exceptional position within NATO. It is the only segment of the alliance where two member states maintain an active, mutual threat perception against one another. It is also the segment most directly exposed to the arc of instability running from the Levant through Iraq to Iran — precisely the theatre now engulfed in conflict.
A credible American withdrawal, or even a structural downgrade of US commitment, would destabilise the southeastern flank along several axes simultaneously.
Turkey: Emancipation or Isolation?
For Ankara, a US exit from NATO would represent both an opportunity and a profound risk. Turkey has spent the better part of a decade hedging between the alliance and autonomous strategic partnerships — most visibly through the acquisition of the Russian S-400 system, its military interventions in Syria and Libya, and its transactional oscillation between Moscow and Washington. A formal American departure could accelerate what Turkish strategic planners have long prepared for: a fully sovereign defence posture unbounded by alliance discipline.
Yet this apparent emancipation would come at a steep cost. Turkey's deterrence posture against Russia in the Black Sea has ultimately rested on the implicit guarantee of collective defence. Without Article 5 credibility, Ankara would face Moscow across the Black Sea littoral without a strategic backstop — precisely as Russian naval and air assets in Syria and Crimea remain operational. Turkey's role as gatekeeper of the Turkish Straits under the Montreux Convention would gain additional geopolitical weight, but leverage without allied backing is a wasting asset.
There is also the Iran dimension. Turkey shares a 534-kilometre border with Iran. The ongoing US–Israeli campaign, and the volatility it has unleashed across the region, places Turkey in an acutely uncomfortable position. Ankara has avoided direct involvement in the conflict, but a NATO collapse would remove the multilateral framework through which Turkey has historically managed its exposure to Middle Eastern conflagrations. The question of Incirlik Air Base — already a friction point — would become existential: does Turkey retain a US facility on its soil outside an alliance framework, or does it leverage the base as a bilateral bargaining chip in an entirely new strategic landscape?
Greece: Exposed on Two Fronts
For Athens, the implications are starker. Greece's primary security concern remains Turkey, and the NATO framework — however imperfectly — has served as a conflict-management mechanism in the Aegean and the Eastern Mediterranean. The alliance has never resolved Greek–Turkish disputes, but it has provided a ceiling on escalation, a channel for American mediation, and a normative environment in which outright coercion carried reputational costs.
Strip that away, and Greece confronts a Turkey that is militarily larger, geographically closer to contested zones, and potentially less constrained. Athens has maintained defence spending above the 2% GDP threshold for years — driven not by alliance solidarity but by the Turkish threat — yet the qualitative gap remains significant, particularly in land forces and drone warfare capabilities where Turkey has made rapid advances.
Greece has responded to earlier signals of American retrenchment by deepening its bilateral defence ties with the US, particularly through the upgraded Mutual Defense Cooperation Agreement (MDCA) and the expansion of the US presence at Souda Bay and Alexandroupoli. The paradox now is clear: these bilateral arrangements were designed to insure against NATO atrophy, yet they depend on an American strategic interest in the Eastern Mediterranean that Trump's rhetoric explicitly calls into question. If the US no longer sees Europe as a "reliable defence partner," the value Washington places on Greek basing facilities is contingent on regional utility — not alliance obligation.
The Alexandroupoli hub, in particular, was conceived as a logistics corridor for US force projection toward the Black Sea and southeastern Europe. Its relevance persists in a US–Russia competition framework but diminishes if Washington pursues a broader withdrawal from the European theatre.
Cyprus, the Eastern Mediterranean, and the Energy Dimension
The ripple effects extend to Cyprus and the wider Eastern Mediterranean energy architecture. The island remains divided, with Turkey maintaining over 35,000 troops in the north. The prospect of NATO dissolution — or even a severe dilution — removes one of the few multilateral frameworks within which the Cyprus problem has been at least nominally addressed. A Turkey unmoored from alliance obligations would face fewer constraints on its posture in the Eastern Mediterranean, including on the delimitation disputes that have pitted Ankara against Athens, Nicosia, Cairo, and Tel Aviv.
The Eastern Mediterranean Gas Forum (EMGF) and associated pipeline and LNG ambitions were already under strain from the regional conflict and Hormuz closure. A simultaneous collapse of the transatlantic security framework would compound investor uncertainty and weaken the strategic rationale for infrastructure projects that depend on regional stability.
The European Defence Question
Trump's rhetoric — and Starmer's pivot toward closer European ties — accelerates the question that Greece and Turkey must answer differently: what does European defence autonomy mean for the southeastern flank?
For Greece, alignment with a Franco-German-led European defence pillar offers a partial hedge, but the EU's collective defence clause (Article 42.7 TEU) lacks the operational credibility and integrated command structure of NATO. Greece would need to invest heavily in European frameworks while managing a neighbour that is formally a NATO ally, a EU candidate, and a strategic competitor — all without American arbitration.
For Turkey, the European defence track is largely foreclosed. Ankara's EU accession process is functionally dead, and its exclusion from European defence-industrial cooperation (particularly the PESCO framework) means it cannot substitute NATO membership with European integration. Turkey would instead be pushed further toward bilateral arrangements — with the US if possible, with Russia or Gulf partners if necessary — and toward a more transactional, less rules-bound regional posture.
The End of Managed Ambiguity
The southeastern flank has long operated under a regime of managed ambiguity: Greece and Turkey are allies on paper and adversaries in practice, with the US serving as the indispensable balancer. Trump's interview does not end this regime overnight, but it accelerates its erosion. The risk is not a single dramatic rupture but a cascading loss of deterrence credibility, escalation management, and strategic predictability across the Aegean, the Eastern Mediterranean, and the Black Sea — the three bodies of water where European security is most directly contested and least adequately addressed by European means alone.
Illustration: Perplexity