Explainer-What is the New START nuclear treaty and why does its expiry matter?

The New Strategic Arms Reduction Treaty, commonly known as New START, represents the final remaining pillar of nuclear arms control between the United States and the Russian Federation. Signed in 2010 by Presidents Barack Obama and Dmitry Medvedev, the treaty restricts the world's two largest nuclear powers to a maximum of 1,550 deployed strategic nuclear warheads and 700 deployed missiles and bombers. Beyond these numerical limits, the agreement established a rigorous verification regime, including on-site inspections and data exchanges, ensuring neither side could covertly expand its arsenal. This transparency has historically functioned as a vital stabilizer, preventing a blind arms race and reducing the risk of nuclear miscalculation. The treaty is currently facing an existential crisis following Russia's formal suspension of its participation in February 2023. While Moscow stated it would technically adhere to the numerical limits until the treaty's official expiration on February 4, 2026, it has ceased the mutual inspections and notifications that provided the U.S. with high-confidence intelligence regarding Russian strategic forces. Washington responded by withholding its own data, effectively blinding both nations. The geopolitical friction stemming from the conflict in Ukraine has further complicated any potential negotiations for a successor agreement, as Russia insists that nuclear stability cannot be discussed in isolation from the broader security landscape. The implications of New START’s expiration without a replacement are profound and potentially catastrophic for global security. For the first time since the early 1970s, there could be no legal constraints on the nuclear arsenals of the U.S. and Russia. Experts warn that this vacuum would likely trigger a modern arms race, exacerbated by the rapid nuclear expansion of China, which is not a party to the treaty. Without the predictability provided by New START, military planners in both Washington and Moscow may feel compelled to assume 'worst-case scenarios,' leading to a massive increase in nuclear spending and a heightened state of global nuclear alert.