The End of New START: What the Expiration of the Last US-Russia Nuclear Treaty Means for Global Security

On February 5, 2026, the last remaining legally binding nuclear arms control treaty between the United States and Russia quietly expired. The lapse of the New Strategic Arms Reduction Treaty (New START) marks a historic shift in global security, ending a continuous 57-year era of formal, negotiated limits on the world's two largest nuclear arsenals that began with the SALT I talks in 1969. For decades, these bilateral agreements provided a structured framework that governed the strategic balance, offering both nations a degree of predictability that helped prevent the Cold War from escalating into a catastrophic nuclear exchange.[1][4]

Despite the monumental nature of this expiration, the immediate aftermath has not triggered a sudden, visible surge in nuclear deployments. Instead, Washington and Moscow have entered what security analysts describe as an unusual and fragile 'holding pattern.' Neither nation is currently legally bound to cap its strategic forces, yet neither has moved to exceed the treaty's central limits. By relying on an informal, unverified restraint, both capitals are attempting to manage the transition and avoid sparking an immediate arms race, even as diplomatic relations remain at their lowest point in decades.[2]

To fully understand what was lost with the treaty's expiration, it is necessary to look at what New START actually accomplished. Signed in Prague in 2010, the agreement imposed strict quantitative ceilings on the nuclear forces of both superpowers. Each side was legally limited to deploying no more than 1,550 strategic nuclear warheads and 700 deployed strategic delivery vehicles, a category that includes intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers assigned to nuclear missions. These caps represented a significant reduction from the massive stockpiles maintained during the height of the Cold War.[3][4]

Crucially, the treaty was not just about numerical limits; it was fundamentally about transparency and predictability. New START mandated a rigorous and highly structured verification regime that required regular data exchanges, notifications of missile movements, the sharing of telemetry data from test flights, and short-notice on-site inspections at sensitive nuclear bases. This unprecedented level of transparency was specifically designed to prevent the kind of worst-case scenario planning that historically fueled uncontrolled arms races, ensuring that neither side could secretly build up its forces without the other knowing.[1][3]

The foundation of that transparency, however, had already been crumbling long before the treaty's formal expiration date. In February 2023, following the full-scale invasion of Ukraine and the resulting collapse of bilateral relations, Russia formally suspended its implementation of the treaty's data exchanges and on-site inspections. While Moscow pledged at the time to continue abiding by the numerical caps, the United States effectively lost its primary mechanism for independently verifying Russian compliance on the ground, forcing military planners to rely entirely on national technical means such as satellite surveillance and electronic intelligence.[2][4]

With the treaty now fully expired, the international focus has shifted to whether this informal, unverified restraint can hold over the long term. In September 2025, Russian President Vladimir Putin proposed that both sides continue observing the treaty's central limits for an additional year, provided the United States made a reciprocal commitment and refrained from actions that Moscow viewed as undermining the strategic balance. However, the Russian proposal notably did not include any offer to resume the suspended verification measures, leaving the pledge entirely reliant on trust.[1]

The U.S. response to this proposal has been highly cautious. While the administration has not formally accepted the one-year extension, it has signaled through diplomatic channels that it will not exceed the historical limits as long as Russia demonstrates similar restraint. U.S. officials have publicly stated that they are seeking a 'new, improved, and modernized' treaty that reflects the current strategic reality, arguing that simply rolling over an unverified framework designed in 2010 does not serve the long-term security interests of the United States or its allies.[1][2]

The primary driver behind the U.S. push for a modernized approach is the rapid and opaque expansion of China's nuclear arsenal. When New START was originally negotiated, the strategic environment was overwhelmingly bilateral, focused almost entirely on the legacy arsenals of Washington and Moscow. Today, U.S. defense planners argue that any future arms control framework must account for a complex three-actor dynamic, as the United States faces the unprecedented prospect of deterring two major nuclear-armed peers simultaneously, fundamentally altering the calculus for how many weapons are required for national defense.[3]

This shifting landscape has led many arms control advocates to warn that the world is entering a highly dangerous new era. Without legally binding caps, both nations possess a significant 'breakout capacity'—the ability to rapidly upload thousands of non-deployed warheads currently held in reserve storage onto their existing delivery systems. In a geopolitical crisis, the lack of direct insight into the adversary's actions could easily lead to misinterpretation, prompting one side to surge its forces defensively, which would in turn trigger a rapid and destabilizing escalation by the other.[1][3]

Conversely, other strategic analysts argue that the expiration of New START does not inevitably guarantee an unconstrained arms race. They suggest that the long history of U.S.-Russia cooperation has established a durable baseline of mutual restraint that transcends formal legal documents. In this view, the future of global nuclear governance may rely less on comprehensive, legally binding treaties and more on pragmatic 'risk management'—a system of informal agreements, reliable crisis communication channels, and unilateral transparency measures driven by the shared recognition of mutual vulnerability.[2]

The lapse of the treaty also creates immediate new challenges for domestic oversight within the United States. Under the provisions of New START, the executive branch was legally required to provide Congress with regular, detailed reports on the composition of Russia's nuclear forces and the status of compliance. With those mandates now expired, lawmakers are actively exploring new provisions in the National Defense Authorization Act to ensure continued intelligence sharing, preventing a dangerous oversight gap just as strategic competition between the major powers begins to heat up.[3]

Ultimately, the expiration of New START forces the international community into uncharted and potentially perilous territory. The legal architecture that successfully structured nuclear deterrence for half a century has dissolved, replaced by a fragile system of voluntary compliance and informal signaling. Whether this transition yields a stable, multipolar deterrence equilibrium or sparks a renewed era of unconstrained nuclear competition will depend entirely on the political choices made in Washington, Moscow, and Beijing over the coming months, as the world navigates the highest nuclear stakes since the end of the Cold War.[2][5]