Arsaces (är'susēz) [key], fl. 250 B.C., founder of the Parthian dynasty of the Arsacids,. which ruled Persia from c.250 B.C. to A.D. 226. Arsaces led a successful revolt against Antiochus II of Syria, when Antiochus was engaged in war with Egypt and trying to put down a revolt in Bactria. Among the other Parthian kings were Tiridates, Mithradates I, Mithradates II, and Phraates IV. Their empire became a formidable rival of the Roman power, but began to decay in the 2d cent. A.D. after Emperor Alexander Severus had invaded the country. The Arsacids were overthrown by a revolt of the Persians under Ardashir I, who in A.D. 226 slew Artabanus IV (Ardawan IV), the last of the Arsacids.
