The civil defense programs in the 1950s were established primarily to protect american communities from:

Nuclear fallout

Explanation:

The Civil defence programs in the 1950s introduced under the Presidency of Harry S.Truman. The purpose of these programs was to protect the civilians from the effects of an attack against the country. Civil defence programs attempted to acquire lodging capacities for people in attacked cities and develop mass evacuation plans for targets of the Soviet Union. Nuclear fallout refers to the radioactive ash and dust formed when a nuclear weapon detonates. The Soviet Union's explosion of atom bomb and missiles created fear in Americans and its possibility to reach the United in a few minutes.

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