The New Strategic Arms Reduction Treaty (New START), signed in 2010 by U.S. President Barack Obama and Russian President Dmitry Medvedev and extended in 2021 by Presidents Joe Biden and Vladimir Putin, is today the last active bilateral arms control agreement linking the world’s two major nuclear powers.
Yet, this crucial treaty will come to an end on February 5, 2026, as it cannot be expanded any longer under its current terms (Meduza 2025). Such expiration will mark the end of a half-century lasting settlement and remove the last legal cap on deployed nuclear warheads.
This article aims to understand the historical evolution of arms control between the two leading powers and the challenges for nuclear stability which stem from the New START’s expiration. Relying on recent journalistic and academic sources, it argues that the expiration of New START could pave the way towards a new nuclear arms race, challenging deterrence and encouraging both vertical and horizontal proliferation.
Historical Perspectives on U.S.–Soviet/Russian Arms Control
The first generation of nuclear weapons control was established during the Détente era as the Strategic Arms Limitation Talks (SALT I) resulted in the 1972 Interim Agreement and the Anti-Ballistic Missile (ABM) Treaty. The former capped strategic delivery systems, while the latter restricted missile defenses to a single site per nation with a straightforward reasoning: by ensuring that neither party could accept a disarming first attack, mutually assured destruction would then strengthen deterrence (Freedman 2003, 287).
Additionally, the 1979 SALT II agreement aimed to reduce the number of strategic launchers to 2,400, and thereafter to 2,150. While both parties had originally signed, the Soviet invasion of Afghanistan led to a refusal from the US to ratify said treaty. Nonetheless, both agreed to abide by its terms until it expired in 1985 without legal effect (Meduza 2025).
In 1987, U.S President Ronald Reagan and Soviet leader Mikhail Gorbachev, aiming to improve bilateral relations and stabilize the global order, signed the Intermediate-Range Nuclear Forces (INF) Treaty. The latter marked a turning point in nuclear weapons control as the first settlement to eliminate an entire class of nuclear weapons. It banned ground-launched missiles with ranges between 500 – 5,500 km and introduced mutual inspections of facilities (Meduza 2025). By 1991, 2,692 missiles had been destroyed (The Conversation 2025).
The treaty also significantly helped decrease tensions in Europe, since the removal of Soviet SS-20 intermediate-range ballistic missiles and the American Pershing II allowed for the stabilization of NATO–Warsaw Pact relations and the easing of Cold War tensions.
However, by the 2010s, mutual violations accusations arose, fragilizing trust and leading the US to withdraw in 2019, under Donald Trump’s first presidency, citing Russia’s 9M729 system as a breach of the accord. NATO supported Washington’s decision, but Moscow insisted its system was compliant (Meduza 2025) and subsequently exited the treaty itself, hence removing another key pillar of nuclear arms control.
Towards the New START: from START I and II to the last cornerstone of arms control
A turning point was reached in 1991 through the ratification of the Strategic Arms Reduction Treaty (START I), which required extensive reductions and verification processes. Restricting both nations to an established 1,600 delivery vehicles and 6,000 warheads, the treaty even survived the fall of the USSR, as Russia took on its duties. Both countries officially certified compliance by 2001.
In parallel, George H.W. Bush and Boris Yeltsin signed START II in 1993, which ratioed warhead ceilings to 3,000–3,500 and prohibited multiple independently targetable reentry vehicles on intercontinental ballistic missiles. However, due to its conditionality upon the ABM Treaty, Russia declared START II unlawful in 2002 after the Bush administration withdrew from the former (The Conversation 2025).
By 2002, a new treaty had emerged: the Moscow Treaty on Strategic Offensive Reductions (SORT), whichimposed a reduction to 1,700–2,200 deployed warheads each by 2012. The settlement, however, lacked concrete verification provisions and became obsolete upon signing of the 2010 New START agreement (Meduza 2025).
This last treaty, signed in 2010 between Presidents Barack Obama and Dmitry Medvedev, and originally scheduled to remain in force until 2021 is today the last remaining in force. Said agreement established strict provisions: “each side could deploy up to 700 intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs), and heavy bombers; up to 800 deployed and non-deployed launchers for ICBMs, SLBMs, and bombers; and no more than 1,550 nuclear warheads on deployed strategic delivery systems” (Meduza 2025). Additionally, it provided guidelines for mutual inspections and data exchanges and prevented strategic offensive weapons from being used on third-country territory.
New START: Fragility and Breakdown
While the treaty was renewed in 2021 under Presidents Biden and Putin, testifying to a willingness to maintain stability, Russia’s invasion of Ukraine in 2022 significantly harmed U.S.-Russia relations.
Western arms shipments to Ukraine led Russia to suspend participation in the New START in February 2023. The country indeed prohibited external inspections and halted data-sharing operations, but nonetheless claimed it remained compliant. While incapable of verifying such information, the U.S. confirmed it appeared to be the case (Meduza 2025).
However, such political moves testified to rising tensions between both countries. Dmitry Medvedev, former President and signatory of the treaty as well as close Putin ally, even argued this suspension was a legitimate punishment stemming from U.S. “dumb anti-Russian” policy (Meduza 2025).
The conflict pushed for exacerbated nuclear brinkmanship. Not only had Putin already put nuclear troops on high alert by 2022, by 2024, non-nuclear aggression backed by nuclear powers was added to Russia’s updated list of nuclear use criteria (Modern Diplomacy 2025). Such a decision testifies to some of the upcoming hardships in nuclear cooperation and to the unlikeliness to come to a deal before the current New START expires.
Current Challenges to Renewal
The Russo-Ukrainian War is a key obstacle in establishing future treaties since Moscow perceives nuclear weapons as a primary source of leverage. It has indeed proven to be powerful as Western restraint in avoiding direct NATO engagement reflects Russia’s nuclear threats. According to Pavel Podvig, director of the Russian Nuclear Forces Project, this has significantly deterred escalation (Meduza 2025).
Yet, renewal of nuclear arms control is further fragilized by the U.S. and Russia’s diverging strategic and diplomatic agendas. While the former has actively sought to engage China into negotiations given its rapid arsenal expansion, the latter prioritizes including France and Britain, notably after President Emmanuel Macron mentioned the potential creation of a “nuclear umbrella” to protect Europe from eventual Russian aggressions. The “Golden Dome” missile defense project announced by Trump in May 2025 to protect the country from aerial risks, notably from its Russian and Chinese counterparts, is also seen as destabilizing (Modern Diplomacy 2025), and may hinder future arms control talks.
Not to mention both sides are constantly modernizing. Yet, these innovations undermine arms control by introducing systems not covered by legacy treaties.
Implications of New START’s Upcoming Expiration
The coming to an end of this last remaining treaty between the U.S. and Russia could very well be the end of an era of strategic nuclear stability. The absence of any legal provision could lead to a rapid doubling of deployed warheads should both countries feel the need for additional protection. With no means to conduct external verifications, trust will erode and fear as well as miscalculations could thus lead to vertical proliferation.
In such context, nuclear deterrence and reassurance would be significantly weakened. Horizontal proliferation would hence reach unprecedented levels as other countries would actively aim to develop nuclear weapons. Germany, South Korea, Saudi Arabia, and Japan (a case especially symbolic as the sole victim of a nuclear attack itself) have all been cited as potential aspirants if U.S. extended deterrence erodes (Meduza 2025).
Furthermore, while currently excluded from this bilateral framework, China, India, Pakistan, North Korea, and Israel also possess nuclear weapons and while holding different powers should thus be included in any future arms control treaty (Modern Diplomacy 2025). Yet, while multilateralism should be a key component in the new arms control regime, China for instance refuses constraints on its arsenal, testifying to some of the hardships in establishing broader coalitions.
Conclusion
The expiration of New START in February 2026 will likely mark the end of the bilateral arms control era that began with SALT I back in 1972.
While past treaties had allowed relative nuclear stability and deterrence through limitations, today’s security landscape is marked by new challenges such as the active conflict in Ukraine, with nuclear as key vessel of Russian strategy, emerging technologies challenging existing legal frameworks and multipolar dynamics, with China rapidly expanding and regional powers reconsidering nuclear options.
The contradiction is clear: while nuclear deterrence has kept NATO and Russia from going to war directly in Ukraine, the same dependence on nuclear signaling undermines arms control mechanisms. The post-2026 order hence likely will be characterized more by competitive rearmament than by restraint unless Washington and Moscow can regain mutual trust and ingeniously integrate new players and technology.
Bibliography
Freedman, Lawrence. The Evolution of Nuclear Strategy. 3rd ed. London: Palgrave, 2003.
Meduza. 2025. “The Last Remaining U.S.–Russia Nuclear Treaty Expires in Less than a Year. A New Arms Race Has Already Begun.” Meduza, April 30, 2025.
Modern Diplomacy. 2025. “The End of New START: Is a New US-Russia Arms Race on the Horizon?” Modern Diplomacy, August 25, 2025.
SIPRI. SIPRI Yearbook 2024: Armaments, Disarmament and International Security. Oxford: Oxford University Press, 2024.
Tannenwald, Nina. The Nuclear Taboo: The United States and the Non-Use of Nuclear Weapons Since 1945. Cambridge: Cambridge University Press, 2020.
The Conversation. 2025. “Russia’s Decision to Pull out of Nuclear Treaty Makes the World More Dangerous.” The Conversation, August 7, 2025. https://theconversation.com/russias-decision-to-pull-out-of-nuclear-treaty-makes-the-world-more-dangerous-262742.
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