The United States Senate ratifies the Anti-Ballistic Missile Treaty.

The Anti-Ballistic Missile (ABM) Treaty was a landmark arms control agreement signed on 26 May 1972 by the United States and the Soviet Union during the Cold War. It was negotiated alongside the first Strategic Arms Limitation Talks (SALT I) and reflected the belief that limiting defensive missile systems would help preserve strategic stability. At the time, both superpowers possessed large and growing nuclear arsenals, and there were concerns that widespread deployment of anti-ballistic missile defenses could encourage an arms race. By restricting such defenses, the treaty sought to maintain the principle of mutually assured destruction (MAD), in which neither side would launch a nuclear first strike because both retained the ability to retaliate.

Under the original treaty, each country was permitted to deploy ABM systems at only two sites: one to defend the national capital and another to protect an intercontinental ballistic missile (ICBM) field, with no more than 100 interceptor missiles at each location. A 1974 protocol further reduced this allowance to just one site per country. The Soviet Union chose to defend Moscow, while the United States briefly operated the Safeguard missile defense system near Grand Forks, North Dakota, to protect an ICBM complex. However, the U.S. system was considered costly and of limited effectiveness, and it was shut down after only a few months of operation.

The ABM Treaty became one of the cornerstones of Cold War arms control, helping to slow the development of nationwide missile defense systems for nearly three decades. Supporters argued that by limiting defensive technologies, the treaty discouraged either side from believing it could survive a nuclear exchange or launch a successful first strike. The agreement also fostered an atmosphere of cooperation that led to later arms control treaties, including the Strategic Arms Reduction Treaties (START). Although advances in missile technology and changing security threats emerged over the years, the treaty remained an important symbol of the effort to reduce the risk of nuclear conflict through negotiated limits.

The treaty came to an end in 2002 after the United States formally withdrew, citing the need to develop missile defenses against emerging threats from so-called rogue states and the possibility of missile attacks by non-state actors. Russia strongly opposed the withdrawal, arguing that the treaty had been essential to maintaining global strategic balance. Following its withdrawal, the United States accelerated the development and deployment of missile defense systems, while Russia and later China expanded and modernized their strategic nuclear forces. The end of the ABM Treaty is widely regarded as a significant turning point in international arms control, contributing to a more complex and competitive era of nuclear deterrence and missile defense.