The New START Treaty Expired — Here's What That Actually Means for Nuclear Risk

On February 5, 2026, the last major bilateral nuclear arms control treaty between the United States and Russia quietly expired. There was no dramatic breakdown, no last-minute walkout. The treaty simply ran out, and with it went the only legally binding framework that capped the world's two largest nuclear arsenals.

The New START Treaty had limited each side to no more than 1,550 deployed strategic nuclear warheads, with deployed missiles and bombers capped at 700 and total launchers at 800 [1]. That represented a nearly two-thirds reduction from the original START agreement. For more than a decade, it provided something concrete: a ceiling, an inspector on the ground, numbers both sides had agreed to honor.

What vanished with the treaty's expiration is not just a piece of paper. It is the inspection regime. Under New START, each side was entitled to 18 on-site inspections per year [1]. Inspectors from both countries had visited warhead storage sites, bomber bases, and submarine ports. They had counted missiles, verified telemetry, confirmed that what both governments claimed about their arsenals was actually true. That layer of transparency is now gone. Neither side has the right to inspect the other's facilities, and neither has an obligation to provide data beyond what it voluntarily chooses to share.

A Long Arc From Cold War Peak to Present Vacuum

The story of nuclear arms control stretches back further than most people realize. When START I was signed on July 31, 1991 by Presidents George H.W. Bush and Mikhail Gorbachev, the Soviet Union still existed and held roughly 12,000 nuclear warheads [2]. The treaty's implementation over the following years removed about 80 percent of all strategic nuclear weapons then in existence. By the time the process concluded after the Soviet collapse, the combined Russian and American inventory had fallen from that Cold War peak to around 3,500 [2]. That was a remarkable accomplishment. Two former adversaries had dismantled the bulk of their strategic forces under international supervision.

START I expired on December 5, 2009, and the negotiations that followed took longer than anyone wanted. Eight rounds of talks in Geneva from May to November 2009 produced enough draft text that Presidents Obama and Medvedev could announce an agreement on March 26, 2010, signing the new treaty in Prague on April 8 [4]. The U.S. Senate ratified it 71 to 26 on December 22, 2010 [1]. It entered into force on February 5, 2011 [1].

That timeline mattered. The treaty replaced the shorter Moscow Treaty, also known as SORT, which was set to expire at the end of 2012 [1]. Without New START in place, there would have been no bilateral ceiling on deployed warheads at all.

There was also START II, signed in January 1993 by Presidents Bush and Yeltsin. It would have banned multiple independently targetable reentry vehicles, MIRVs, on intercontinental ballistic missiles [3]. But it never entered into force. Russia withdrew after the United States withdrew from the Anti-Ballistic Missile Treaty in 2002 [3]. That history matters when considering what comes next. Arms control agreements require both sides to see them as serving their interests. When one side decides the strategic environment has shifted, treaties collapse.

What Russia Did Before the Expiration

The expiration did not come as a surprise. Russia had already signaled the direction of travel. On February 21, 2023, Moscow suspended its participation in New START, stating it would continue to abide by the numerical limits [1]. It was a deliberate act, framed domestically as a response to Western support for Ukraine, but one that had been building for years as relations deteriorated.

The claim that Russia continues to observe the 1,550 warhead ceiling is impossible to verify independently. Without inspections, there is no mechanism for the United States to confirm whether Russian deployed forces have remained within treaty limits. Russia could expand its arsenal, move warheads from storage to deployment, or alter the composition of its strategic forces in ways that would be invisible to Washington.

The Gaps the Treaty Never Covered

New START was always narrow in one important respect. It governed deployed strategic nuclear weapons, the warheads sitting on missiles and bombers that could reach the continental United States or Russia. It said nothing about the tactical nuclear warheads Russia maintains, many of them stored at facilities far from any missile silo [1]. American tactical nuclear weapons, fewer in number and concentrated in Europe, were also outside the treaty's scope.

The treaty's 1,550 ceiling applied only to deployed warheads. Both sides maintained thousands more in storage, available for rapid deployment if circumstances demanded. New START did not cap the total size of either nation's nuclear stockpile, only the portion sitting on delivery systems at any given time. That distinction matters enormously when evaluating what "no limits" now means.

Russian officials have been explicit that they view the nuclear balance through a broader lens than New START ever addressed. Moscow has invested heavily in new delivery systems, including submarine-launched ballistic missiles, hypersonic glide vehicles, and air-launched cruise missiles. Some of those systems are designed specifically to evade missile defenses. The treaty was built around a framework where both sides had predictable, countable arsenals. The strategic reality has moved faster than the treaty architecture.

What Experts Fear Could Happen Next

Nuclear analysts identify several distinct risks that emerge from treaty expiration. The first is an unchecked arms race. Without a ceiling, both sides face incentives to build more. Russia has signaled interest in deploying more submarine-based warheads. The United States has modernization programs underway for all three legs of its nuclear triad. If both sides pursue qualitative and quantitative improvements simultaneously, the stability that arms control was designed to preserve begins to erode.

A second concern involves miscalculation. Treaties create predictability. When a leader in Moscow or Washington considers a military action, they can estimate with some confidence how the other side will respond because both sides understand the size and composition of each other's arsenals. Without that common framework, uncertainty grows. Each side must guess what the other has, what it might use, and what response it should expect. Miscalculation during a crisis becomes more likely when neither side has reliable information about the other's actual forces.

The third risk is more subtle: the normalization of nuclear competition. Arms control treaties encode a norm that nuclear rivalry is something to be managed, not accepted as permanent. Their absence shifts the baseline. Policymakers in both countries may come to view an unregulated nuclear competition as normal rather than dangerous, reducing pressure to negotiate new constraints.

Former weapons inspectors and retired military officers have described the loss of on-site inspections in particular terms. They speak of the danger of returning to a world where each side develops weapons and strategies in secret, where surprises become possible in ways they have not been for decades. The Cold War produced that world once. The memory of what it nearly caused has not faded.

What Could Replace the Treaty

Some analysts argue the treaty was already becoming irrelevant before it expired. Russia suspended participation in 2023, and the United States had limited ability to verify Russian declarations even before that date. The practical architecture of arms control had already broken down. What expired was the legal framework, not the actual transparency.

What could replace it is unclear. Negotiations require both sides to see value in an agreement and trust enough to engage in good faith. Neither condition exists comfortably at present. Ukraine has fundamentally altered how Moscow's relationship with Western security institutions. The United States has its own domestic politics to navigate, with skepticism of arms control treaties running through portions of the political spectrum.

There are more modest possibilities. Agreements on nuclear risk reduction, limiting specific systems rather than overall warhead counts, might be more achievable than a comprehensive treaty. Hotline communications between nuclear commands could be modernized and expanded. Both sides could voluntarily publish nuclear stockpile numbers, preserving some transparency without a binding inspection regime.

But the deeper question is whether either side has sufficient interest in the kind of mutual restraint that arms control requires. New START worked because both the United States and the Soviet Union, later Russia, saw value in limiting the other side's forces while limiting their own. That bargain is not dead, but it is under more pressure than at any point since the Cold War.