After Prophet Muhammad’s death in 632 AD, Abu Bekr, his first successor and the first Caliph of the Muslims, tried to put an end to all the fights and disputes among the Muslims and reunite all the Muslim nations. In his attempts to spread Islam and bring all the nearby land under the Arabs’ control, the first sparkle of the Arab conquest of Persia was lit.
The second Muslim Caliph, Umar, set a campaign against Persia and after several battles, Yazdegerd III, the last Sassanid king who never had such a power as that of the previous king, khusrau II, fled to different districts of Iran and finally got killed by a miller. Having taken Mesopotamia, the Arabs occupied Ctesiphon, the capital of Sassanid dynasty in 637 and in some years, the Arabs pushed eastwards and the eastern parts of Persia were also occupied. The Sassanid Empire was totally toppled in Nahavand battle in 641 AD and the Umayyad dynasty, which was of a purely Arabic nature, was established in Persia. Because of peoples’ dissatisfaction of the situation through the battle years and the fair treatment of Islam toward them, the Persians who were mostly Zoroastrians gradually converted to Islam.
The Arabs tried to change the Iranian’s Persian way of life and impose their own manners, traditions, habits, politics, rules, etc. on the Iranians and they announced Arabic as the official language of the country. Iranians never accepted a totally Arabic culture and language; however, both Persians and Arabs adopted some customs and traditions of the other. So the two cultures got intermingled and a new Islamic Persian culture was founded.