Almost all surviving Tibetan ancestor myths and pre-dynastic histories were compiled or, with the aid of Bon, revised during the time of Srong Btsan Sgam Po. After Srong Btsan set up a powerful and centralized monarchy, a task that had begun with his grandfather, political legitimacy, cultural integration and national identity came to the fore as urgent priorities. As a well-developed belief system born of the merging of imported Persian religion and local beliefs, Bon was well suited to meeting these needs. It offered new intellectual and spiritual resources that enabled the Srong Btsans to overcome tradition and bring cohesion to the Tibetan people.
