Sassanidae, a dynasty of Persian kings founded by Ardeshir, called by the Greeks Artax-erxes, and considered the son of Babek and the grandson of Sassan, who overthrew the rule of the Arsacidae, in A. D. 226. (See Ardeshir, and Persia.) Under the Sassanian kings, and especially under Sapor (Shapur) I., Sapor II., Chosroes (Khosru) I., and Chosroes II., long and successful wars were carried on against the Roman and Byzantine emperors, the Persian empire was extended and consolidated, and the Zoroastrian religion was restored and maintained. The dynasty closed with Yezdegerd III., who in 641 was beaten by the caliph Omar in the battle of Nehavend, into which the Persians went 150,000 strong; he was murdered in 651 while asleep, for the sake of his splendid garments, by a miller in whose mill he had hidden. From the coins of this dynasty, of which an almost complete series has been gathered, it appears that the kings were men of extraordinary personal beauty, with large eyes, prominent well formed nose, and firm chiselled mouth. On some of the coins an eldest son or a queen is associated with the monarch.