I didn't pitch the campaign that way and the individual PC's actions were completely unexpected by all of us. For some reason, one of the PCs got it into their head that their home city was just as bad as the mutant city to the west and the cyborg city to the east who had joined forces to wipe their home city out. And while the home city wasn't exactly a shining beacon on the hill, the mutants to the west wanted to commit genocide and the cyborgs to the east wanted to enslave everyone. So a fight broke out when one of the PCs tried to destroy the nuclear football that belonged to the last president of the United States. During the fight, one of the other PCs thought it was a good idea to start lobbing grenades into melee. This ended up destroying the nuclear football, the PC who started it was killed, and at the end of the campaign the city was wiped out by the combined forces of the mutants and cyborgs. It wasn't a total loss though, the PCs managed to remove a world wide threat at the end. It just cost them their home and the 10,000 people who lived there.