This thesis chronicles and examines the development of civil defense under the Truman administration. Both Washington's politicians and various atomic scientists embraced civil defense planning as a method of combating the Cold War and ensuring domestic national security. These efforts resulted in the Federal Civil Defense Administration (FCDA). The FCDA was the product of unrealistic assumptions and poor planning. Congress consistently allotted the agency unsubstantial yearly operating budgets, and consequently the FCDA always remained in the shadow of the larger military effort. Under the Truman administration, the FCDA was materially unsuccessful, because its nationwide shelter program never came to fruition. The civil defense administration's public information program, however, was modestly successful in that it raised public awareness of the possibility of atomic attack. / Master of Arts