In the year 640 Emperor Yazdegerd III was captured in battle at the Siege of Mecca and taken away to spend the rest of his days as a Roman prisoner. Although he left behind an infant son, Firuz, real authority was held by his cousin Shahryar who quickly set about eliminating Yazdegerd-loyalists before having himself enthroned as emperor. Firuz and his guardians fled into exile in India after Shahryar tried to have him assassinated, and he grew up under the protection of the Gupta court. In 718 Firuz' son Narsieh invaded Persia in a two-pronged attack by land and sea...