During the Cold War era, the developments of nuclear arsenals of the U.S. and the Soviet Union and their fierce competition raised the urgency of nuclear arms control between the two superpowers. Although the two sides held different positions in both theory and practice about nuclear deterrence and nuclear arms control, they shared a common understanding of avoiding a nuclear war and the necessity of nuclear arms control. That shared understanding was a prerequisite to their cooperation on limiting strategic weapons and materialized on the conclusion of the First Strategic Arms Limitations Talks (SALT I). However, negotiations on strategic nuclear weapons were not conducted in a vacuum, the shared understanding between the U.S. and the Soviet Union on nuclear arms control continued to evolve as the strategic balance shifted, new weapons technology was developed, and different political and military needs arose. Interests, ideas, and rational choices interacted closely with each other and together determined the cooperation on nuclear arms control.