Antiochus spent the final years of his life attempting to reclaim the lost eastern territories, overrun by the Parthians under their "Great King", Mithridates I. Marching east, with what would prove to be the last great Seleucid royal army (including a unit of Judean troops under John Hyrcanus), he defeated Mithridates in two battles, killing the aged Parthian king in the latter of these. He restored Mesopotamia, Babylonia and Media to the Seleucid empire, before dispersing his army into winter quarters.