Why did the United States and the Soviet Union negotiate arms-control agreements during the Cold War?

During the Cold War, the United States and the Soviet Union negotiated arms-control agreements primarily to manage the existential threat posed by their massive nuclear weapons arsenals. The prospect of mutual destruction in an intercontinental nuclear exchange drove both superpowers to seek ways to limit the testing, deployment, and eventual possession of these weapons.1

Key motivations and factors included:

• Strategic Stability and Deterrence: Many agreements were predicated on the strategy of mutually assured destruction, which held that the threat of an overwhelming counterattack would prevent an initial strike. By limiting defensive systems like antiballistic missiles, such as in the ABM Treaty, both sides ensured they remained vulnerable, thereby reinforcing the deterrent effect of their offensive forces.1234
• Crisis Management: Following the Cuban missile crisis, which brought the world to the brink of nuclear war, both nations recognized the urgent need for diplomatic communication and risk-reduction measures to avert catastrophe.152
• Preventing Proliferation: Superpowers sought to control the spread of nuclear technology to other nations, leading to agreements like the Treaty on the Non-proliferation of Nuclear Weapons.1
• Economic and Political Factors: Negotiations were often influenced by changing political climates, such as the policy of détente, and the need to manage the high costs and risks associated with an unchecked arms race.134