Nuclear Arms Control Treaties

The Limited Test Ban Treaty of 1963, signed after the Cuban Missile Crisis, banned nuclear tests in the atmosphere, in space, and under water. The Nuclear Non-Proliferation Treaty, in force since 1970, commits countries without nuclear weapons not to acquire them and the five recognized nuclear powers to pursue disarmament, and it has 191 parties. Beginning with the SALT I agreements and the Anti-Ballistic Missile Treaty of 1972, the United States and the Soviet Union capped strategic forces, and the Intermediate-Range Nuclear Forces Treaty of 1987 eliminated an entire class of missiles. The START treaties that began in 1991 cut deployed arsenals far below their Cold War size.

As treaties, these agreements needed approval by two-thirds of the Senate, which consented to the test ban, the nonproliferation treaty, and New START but rejected the Comprehensive Nuclear-Test-Ban Treaty in October 1999. The United States has not conducted a nuclear explosive test since September 1992, maintaining its weapons through computer simulation and experiments at the national laboratories. It withdrew from the Anti-Ballistic Missile Treaty in 2002 and from the INF Treaty in 2019, citing Russian violations. New START, signed in 2010 and extended in 2021, limited each side to 1,550 deployed strategic warheads and allowed on-site inspections, which Russia suspended in 2023.

New START expired on February 5, 2026, leaving the two largest nuclear powers without limits on their arsenals for the first time since the early 1970s. Russia said it would keep to the limits as long as the United States did, while U.S. officials said there was no formal understanding and that any new agreement must include China, whose arsenal is growing quickly. In October 2025 the President ordered preparations to resume nuclear testing on an equal basis with other countries. No U.S. nuclear explosive test had taken place as of November 2026, though a non-nuclear high-explosive experiment was conducted at the Nevada test site in September 2026. Supporters of arms control say treaties reduce the risk of war and the cost of an arms race, while skeptics say they constrained the United States while rivals cheated or stayed outside them.