A Master or Enclave campaign Event?
Fallout: Phoenix - The World and humanity burst into flames (literally) and crashed down into ashes, only to rise up once again. (Vaults and The Master are important in this campaign)
Short summary, this campaign is the Resource Wars but starts from 2060 and up to 2243.
Fallout: Rising Sun - A mysterious force known only as the Enclave has begun to rise, and many have found reason to be afraid.
There arn't many playable factions in Rising Sun but you can play as The Enclave, NCR, Vault City, and Reno currently, i'm still adding in things.
Fallout: War - The world was at war and the world had suffered, the world had faced death and yet it endured; But War... War Never Changes.
Half of the Phoenix Campaign and all of the Rising Sun, but with alot of extra features along with alot of removed ones... this is the main campaign, but the other two are more for focusing on seperate parts.
EDIT: To answer your question, that event was one of the Factions opening events.