"The progress of Civil Defense at Federal, State and local levels during 1953 should be assessed against the momentous events of the year. When the new administration took office, it was an accepted fact that the United States had not had a monopoly on atomic weapons since 1949. However, there had been no recent confirmations of actual atomic tests by the Russians. The British were known to be proceeding independently with the development of atomic weapons and the study of their effects. No other nation had engineered a successful atomic explosion. There had been some rumored reports of successful American experiments with a hydrogen device in the Pacific. As the new year began, however, these had not been confirmed officially by either the Atomic Energy Commission or the Department of Defense. A statement released by the AEC on November 10, 1952, had said only, '...the test program included experiments contributing to thermonuclear weapons research'. A series of atomic tests was being readied at Yucca Flats in Nevada. An important feature of these tests was to be the measurement of a number of damage effects important to Civil Defense. Then, on March 17, 1953, the entire Nation witnessed-on live television and newsreel films-the detonation of an actual atomic bomb and its effects on sample American homes, cars, and house furnishings. Department store mannequins represented live men, women, and children in this graphic demonstration. Thus, for the first time, Americans everywhere were able to see for themselves both the tremendous explosive power of such a bomb, and the actual tests of shelter precautions which could increase their personal chances for survival in an atomic attack."
United States Emergency Management Institute: http://training.fema.gov/EMIWeb/edu/