New START Expiry: Implications for Europe

Why It Matters

The loss of New START erodes confidence in US nuclear guarantees to Europe and signals a broader erosion of arms‑control architecture, heightening strategic uncertainty across the trans‑Atlantic alliance.

Key Takeaways

• New START expired, ending last US‑Russia strategic arms treaty
• US‑Russia limits may persist via informal “handshake” agreement
• Treaty did not constrain theater nuclear forces threatening Europe
• Russian modernization targets US missile defenses, raising escalation risk
• China’s expanding arsenal hampers future multilateral arms‑control efforts

Pulse Analysis

The expiration of New START marks a watershed moment in post‑Cold‑War arms control. For decades, the treaty provided a transparent framework that limited the size of the US and Russian strategic arsenals and facilitated data exchanges, on‑site inspections, and confidence‑building measures. Its disappearance removes a rare channel of dialogue between the two nuclear powers, forcing policymakers to rely on ad‑hoc arrangements that lack verification rigor. In an environment where both sides are pursuing costly modernization programs, the absence of a formal cap could accelerate an unchecked buildup, complicating crisis management and increasing the risk of miscalculation.

Europe feels the reverberations most acutely. While New START did not regulate theatre‑level nuclear weapons—systems that Russia can deploy against NATO members—the treaty underpinned the broader credibility of US extended deterrence. Without a binding framework, European leaders confront growing doubts about Washington’s ability to limit escalation and protect allies from limited nuclear use. This uncertainty fuels debates in several European capitals about developing indigenous nuclear capabilities, a shift that could further destabilize the regional security architecture and provoke Russian countermeasures.

The strategic landscape is now truly triangular, with China’s rapidly expanding nuclear force adding a new dimension to deterrence calculations. Both Moscow and Washington must factor a third nuclear actor into their force‑posture decisions, making bilateral arms‑control solutions increasingly untenable. Future agreements will likely need to incorporate China and perhaps NATO nuclear states to remain viable, but political will remains scarce. Europe’s pragmatic path may involve bolstering conventional strike capacities, deepening missile‑defence cooperation, and investing in resilient command‑and‑control systems to preserve deterrence credibility amid an evolving, multilateral nuclear environment.