Question

which policy or initiative contributed most to the nuclear arms race between the united states and the soviet union?

Answer 1

The competition for supremacy in nuclear warfare between United States and the Soviet Union together with their respective allies during the Cold War was called nuclear arms race.

The second strike where sides, the US and SU developed a capability to launch devastating attack after sustaining a full assault from other side was part of what became known as the Mutual Assured Destruction.