The Battle of al-Qadisiyyah fought in 636, was the decisive engagement between the Arab Muslim army and the Sassanid Persian army during the first period of Muslim expansion. It resulted in the Islamic conquest of Persia and was key to the conquest of Iraq. The battle also saw the alleged alliance of Emperor Yazdegerd III with Byzantine Emperor Heraclius, who married his granddaughter Manyanh to Yazdegerd as a symbol of alliance. The last Persian emperor was Yazdgerd III, who was killed in 653 during the reign of the Caliph Uthman. His death officially marks the end of the Sassanid royal lineage and empire.
