Complex sentence: After being crowned at Tabriz in 1501, Shah Isma'il Safavi determined that the Ithna Ashari branch of Shi'a sect of Islam announced the only accepted sect in Iran, as a result of this royal order the mostly Sunni population of Tabriz converted to Shia.
Split into simpler sentences: After being crowned at Tabriz in 1501, Shah Ismail Safavi announced the Ithna Ashari branch of Shia Islam the only accepted sect in Iran. As a result of this royal order, the mostly Sunni population of Tabriz converted to Shia.