... the game-plan of deterrence during the Cold War was always complex. One of the most complex and controversial areas of this on-going chess game was that of Civil Defense. The protection of civilian lives and the survival of a nations economic and industrial infrastructure. The extent to which a nation can live on and raise itself from the ruins of a full-scale nuclear conflict was seen by many strategists as vital to the believability of the concept of deterrence. Many wondered if the threat of unleashing worldwide holocaust, and the certain destruction of one's own homeland, in response to an Russian invasion of Europe or even the one city of Berlin was plausible. Did the USSR really believe that a US President would start a nuclear war over certain 'lines drawn in the sand'?
In the late 1950's there were studies undertaken regarding what would be involved for a truly robust Civil Defense strategy designed to save the lives of the most American citizens. If nuclear war did not mean death of most Americans would our atomic forces be a much more realistic and believable deterrent to Soviet aggression?
The blog Atomic Skies offers an in depth look at a fascinating study by some of the leading 'think-tank' on the possibility of shielding the entire population of Manhattan from multiple strikes of high yield Hydrogen Bombs. (link to the entire article here)
You really should read the entire article to get a sense for the detail and science-fiction like concepts.