 Soon after, however, a Parthian tribal chief called Arsaces invaded the Parthian territory around 238 BC to form the Arsacid dynasty, from which the Parthian Empire originated.Antiochus II's son Seleucus II Callinicus came to the throne around 246 BC.Seleucus II was soon dramatically defeated in the Third Syrian War against Ptolemy III of Egypt and then had to fight a civil war against his own brother Antiochus Hierax.