With Cold War tensions heightening at the start of the 1960s, the superpowers are drawn into an escalating arms race. The world's safety depends on a nuclear paradox known as "mutual assured destruction."

In the 1960s, as dissent and protest swept through the West, nations of the Warsaw Pact were experimenting with reforms. But hopes for change were crushed by palace coups and, in the case of Czechoslovakia, outright invasion.