Duck And Cover

I'm sure the dog tags was related to the fear of nuclear war in the 50's and 60's

Duck and Cover was a suggested method of personal protection against the effects of a nuclear weapon which the United States government taught to generations of United States school children from the late 1940s into the 1980s. This was supposed to protect them in the event of an unexpected nuclear attack which, they were told, could come at any time without warning. Immediately after they saw a flash they had to stop what they were doing and get on the ground under some cover—such as a table, or at least next to a wall—and assume the fetal position, lying face-down and covering their heads with their hands. Similar instructions were given in 1964 in the United Kingdom by Civil Defence Information Bulletin No. 5. and, in the 1980s, by the Protect and Survive series.
Proponents argued that thousands could be saved through this precaution, without which people would instead run to windows to find the source of the big flash. During this time a shock wave would cause a glass implosion, shredding onlookers.
Similarly, "Drop, Cover and Hold On" is taught in areas prone to earthquakes. Schools in some tornado-prone areas of the United States also practice tornado drills that involve children squatting and covering the backs of their heads.
The United States' monopoly on nuclear weapons was broken in 1949 when the Soviet Union tested its first nuclear device, and many in the government and public perceived that the United States was more vulnerable than it had ever been before. Duck-and-cover exercises quickly became a part of Civil Defense drills that every American citizen, from children to the elderly, practiced to be ready in the event of nuclear war. In 1950, during the first big Civil Defense push of the Cold War; the movie Duck and Cover was produced (by the Federal Civil Defense Administration) for school showings in 1951. At the time, it was believed the main dangers of a Hiroshima-type nuclear blast were from heat and blast damage: radioactive fallout itself was not clearly identified until 1954, after the Castle Bravo nuclear-weapon test in the Marshall Islands caused sickness and death in Japanese fishermen on the Lucky Dragon fishing vessel.
The advice to "duck and cover" holds well in many situations where structural destabilization or debris may be expected, such as during an earthquake or tornado. At a sufficient distance from a nuclear explosion, the shock wave would produce similar results and ducking and covering would perhaps prove adequate. It would protect the face (particularly the eyes) from the intense heat of a detonation. It would also offer some protection from flying glass and other small, but dangerous, debris. However, within a considerable radius—depending on the explosion's height and yield—ducking and covering would offer negligible protection against the intense heat, shock waves, and radiation following a nuclear explosion. People in this range would have little opportunity to duck and cover before being killed by the blast. The technique offers no protection against fallout. However, the technique assumes that after the initial blast, a person who ducks and covers will move to a more sheltered area. It is a first response only.
In U.S. Army basic training in the 1970s, soldiers were taught to fall immediately down, covering face and hands and using their bodies to shield their weapons from the heat of the blast.
The exercises of civil defense are now seen as having less practical use than psychological use: to keep the danger of nuclear war high on the public mind, while also attempting to assure the American people that something could be done to defend against nuclear attack.
These messages, including children's songs, were used to educate the young public in case of nuclear attack.
Ducking and covering does have certain applications in other, more natural disasters. In states prone to tornadoes, school children are urged to 'duck and cover' against a solid inner wall of a school, if time does not permit seeking better shelter—such as a storm cellar—during a tornado warning. The tactic is also widely practiced in schools in states along the West Coast of the United States, where earthquakes are commonplace. Ducking and covering in either scenario would theoretically afford significant protection from falling or flying debris.
In an earthquake, people are encouraged to "drop, cover, and hold on": to get underneath a piece of furniture, cover their heads and hold onto the furniture. This advice also encourages people not to run out of a shaking building, because a large majority of earthquake injuries are due to broken bones from people falling and tripping during shaking. While it is unlikely that "drop, cover and hold on" will protect against a building collapse, buildings built in earthquake-prone areas in the United States are usually built to earthquake "Life Safety" codes[citation needed], and a building collapse (even during an earthquake) is rare. "Drop, cover and hold on" may not be appropriate for all locations or building types, but many experts agree it is the appropriate emergency response to an earthquake in the United States.