Abbas I of Persia
Shiism did not become fully established until the reign of Abbas I of Persia (1587–1629). Abbas hated the Sunnis, and forced the population to accept Twelver Shiism. Thus by 1602 most of the formerly Sunnis of Iran had accepted Shiism. A significant number, however, did not accept Safavid rule, prompting Abbas to institute a number of administrative changes in order to further transform Iran into a Twelver Shia state.