Fan Theory Time: What if Vault-Tec were the ones who helped kickstart the Great War in the Fallout series? They needed a justifiable reason for unknowing people to willingly enter their vaults so they can perform their experiments, after all.

@Chameloshi: The vault experiments were to help the Enclave learn how people would react to scenarios involving prolonged isolation as they survived in orbit. The Enclave only existed to protect themselves from nuclear war; they had no motive to start it.

@Chameloshi: You could ask Mr. House. He knew enough to predict the time they'd drop within an error of less than a day. He probably knew who was behind it. He also knew enough not to apply for a spot in any Vault.

@Chameloshi: I've heard theories that the aliens you meet in FO3 Mothership Zeta are the ones who started the war.