Europe faces uncertainty as New START ends

European leaders are beginning to recognize that the United States may be unlikely to prioritize European security as it did during the Cold War and its immediate aftermath. Following U.S. President Donald Trump’s escalating threats of aggression toward Greenland, European Union foreign policy chief Kaja Kallas said last month that Europe must adapt to new realities and that “NATO needs to become more European to maintain its strength.

The expiration of the final bilateral nuclear arms control agreement between the United States, which serves as NATO’s nuclear guarantor, and Russia, Europe’s principal security threat, leaves European countries in a precarious security position. Some European leaders are considering whether this new uncertainty requires unprecedented action.

The New Strategic Arms Reduction Treaty (New START), the last major U.S.-Russia nuclear arms control agreement, expired February 5, 2026. The treaty limited the number of nuclear warheads each country could deploy on strategic systems to 1,550. Although Russia and the United States were reportedly conducting last-minute negotiations to informally abide by the numerical limits after the treaty’s expiration, Trump renewed uncertainty about the agreement’s future when he posted on social media that New START was a “badly negotiated deal” and that the United States should “work on a new, improved, and modernized Treaty. Barring an agreement, some experts predict that in the coming decade, the U.S. and Russian nuclear arsenals could grow to as many as 3,500 and 2,600 deployed strategic warheads,respectively. Despite not being parties to the agreement, European leaders consider New START a “crucial contribution to international and European security.”

Read more at Council on Foreign Relations