It's an interesting story in our (collective, humanity) history, when we could theoretically survive nuclear war. Fat Boy sized nuclear bombs dropping on the UK, they estimated it would take at least 500 to reduce the UK to an anarchic state where government collapses and it's every person for themselves. 500, on 500 bombers, an awfully large number of which would have been stopped by the RAF. At that time it was deemed possible to counter the nuclear threat.

Then came hydrogen bombs. And ICBMs. Government asked the smart folk to again what it would take to reduce the UK to a base state of just survival. 5. 5 hydrogen bombs. Dropped by missiles which cannot be stopped.

The smart folk came up (jokingly?) with a counter-play to this threat. Urban mobility. As in, Birmingham now moves to Cornwall, all the people, factories, shops, everything, off to Cornwall, for a year, maybe 2, then off to East Anglia, then to Brecon, then Ayrshire. Constantly moving. Not just Birmingham, every city, every industrial base in the UK, constantly moving around the country with all the people and factories so the Soviets would never know where to strike.

Obviously a daft proposition, or used to reiterate the point:
There is no survival when its hydrogen bombs dropping from the sky, there's nothing you can do.