What was the name of the US war plan for a nuclear attack on the Soviet Union in the early 1950s?

The US war plan for a possible nuclear attack on the Soviet Union was called Operation Dropshot.

Prepared in 1949, Dropshot was a contingency plan for a potential large-scale war between the United States and the Soviet Union. It envisioned a conflict involving conventional forces as well as nuclear weapons, particularly if Soviet forces attacked or occupied parts of Western Europe, the Near East, or East Asia.

The plan’s widely cited outline imagined using roughly 300 nuclear bombs and 29,000 high-explosive bombs against targets across the Soviet Union. It was a planning document, not an operation that was carried out, and its assumptions reflected the limited US nuclear arsenal and bomber technology of the early Cold War.

Dropshot is often confused with Operation Unthinkable, the British 1945 plan concerning a possible war with the Soviet Union, or Chrome Dome, a later US airborne nuclear-alert mission. Dropshot was withdrawn in 1951 and replaced by other war plans.