The Cold War was the tense time when 'mysterious' became the default setting for international affairs. Two great superpowers stood toe-to-toe, each with the ability to obliterate the world as we know it. Spies slunk through iron curtains, bodies washed up in rivers and no-one was really sure what was going on.
Today, that frigid climate has thawed and released archives that have given us a reasonably accurate historical record of those years. Yet some Cold War mysteries still loom large in the public consciousness.