The second great conquerors were the Arab Muslims, arising from Saudi Arabia in 640 . They gradually melded with the Iranian peoples, and in 750, a revolution emanating from Iranian territory assured the Persianization of the Islamic world through the establishment of the great Abbassid Empire at Baghdad. The next conquerors were successive waves of Turkish peoples starting in the eleventh century. They established courts in the northeastern region of Khorassan, founding several great cities. They became patrons of Persian literature, art, and architecture.