 Once he was king, Tryphon expanded his control to at least Ptolemais-Akke and Dor.Demetrius, meanwhile, had journeyed east in 139/8 to fight the Parthians, who had seized control of Mesopotamia the previous year.He was defeated and captured by them July or August of 138 BC, leaving Tryphon as uncontested ruler of the remaining Seleucid territories.