On June 14, 1954, cities across America stopped to practice civil defense drills in "Operation Alert," in preparation for a potential nuclear attack by the Soviet Union

Protecting Yourself from Radiation | US EPA

In 1958, the United States conducted a series of nuclear tests known as Operation Hardtack I in the Pacific Ocean, aimed at studying the effects of atomic explosions in different environments. Among the most striking was an underwater detonation at Enewetak Atoll in the Marshall Islands, where a nuclear device was exploded beneath the surface to observe how water, shock waves, and radiation would behave in a marine setting. The blast created a towering column of water thousands of feet high and

The Environmental Effects of Nuclear Radiation | Britannica