Why did the Anti-Ballistic Missile Treaty support mutually assured destruction?

The Anti-Ballistic Missile Treaty (ABM Treaty) supported the concept of mutual assured destruction (MAD) by intentionally limiting the ability of the United States and the Soviet Union to defend their territories against nuclear attack.1

By restricting each superpower to a minimal number of defensive interceptor systems, the treaty ensured that both nations remained vulnerable to the other's strategic nuclear forces. This vulnerability was fundamental to the logic of MAD: if neither side could effectively shield itself from a retaliatory strike, the prospect of total annihilation served as a powerful deterrent against either party initiating a nuclear conflict.12

Proponents of this arrangement argued that maintaining this state of mutual vulnerability prevented the development of a "winnable" nuclear war scenario, which might otherwise have encouraged one side to launch a preemptive strike. Consequently, the treaty sought to preserve the strategic stalemate that defined the Cold War era by preventing the deployment of nationwide missile defenses that would have undermined this delicate balance of terror.12