In the long history of humanity there was never a war as immense and destructive as the Great War of 2077. The entire world was involved in massive Resource Wars, which ended when one of the countries launched a nuclear missile, triggering the Great War. Every country that had any nuclear bombs launched them all at their foes. In two brief hours the entire Earth's arsenal of nuclear arms was detonated and most of the planet's face was turned into cinders. Cities were destroyed, landscapes were shattered, and under the hellish rain of nuclear bombs, the Earth itself started to move, causing great earthquakes that thrust new mountain ranges into existence and destroyed old ones. In two brief hours of bombardment, the face of the planet changed drastically. But that was still not the worst part. A week later, a black rain started falling from the sky. It was a poisonous rain, contaminated with ash and radioactive elements. And during this fallout of inconceivable magnitude, most living things in Earth died. Most of what was left was a deranged, mutated mockery of the world before the Great War.
However, not all things died. Aside from those who survived by mutating, there were those who were saved. The people of the world had predicted something like this would happen and have taken precautions. In the USA, a network of massive underground nuclear fallout shelters were constructed, and these shelters, called 'vaults', were able to provide food, water, shelter and electricity for over a thousand people each for at least a few decades, maybe even centuries. There were other minor bunkers and sanctuaries where not only humans survived the disaster. Once the initial chaos was over and the radiation levels fell low enough, some survivors opened up their shelters and took a glimpse at what has become of the world. And the world had changed beyond recognition and beyond the point of return: the human civilization has fallen, their cities destroyed by the nuclear fire. Dangerous mutants stalked all moving things, and crazed human survivors roamed the remains of their planet killing, looting, and enslaving. The Earth itself became a massive wasteland: an endless expanse of sand and rock, with small, ragged pockets of life scattered here and there. People in the vaults knew this would be the inevitable result of the Great War, and often time they would not call it 'war', but 'holocaust' instead, for the conflict of 2077 had no winner, only victims.
The people of Vault 13 have lived with no knowledge of the outside world for over eighty years since the bombs. There were none left who remembered the world before the holocaust and not many who wanted to venture outside into the inhospitable place they knew the world would turn into after such a disaster. After all, it was their vault, the one they were born in and the one they will die in, their little slice of heaven in the hell man made of Earth.
84 years after that tragic day the people of Vault 13, content to stay underground forever, were despite their wishes forced to look up into the hell above and pray that the endless expanse of California Wasteland would hold the key to their salvation.