Upon the end of the Byzantine–Sasanian War of 602–628, Heraclius travelled through Arbayistan as part of the agreed withdrawal from Sasanian territory. A pretender to the Sasanian throne, Hormizd VI, briefly occupied Nisibis from 630 to 632. After the Muslim victory at the Battle of Jalula in April 637, Muslim forces marched north and established control over Sasanian Upper Mesopotamia, and annexed Arbayistan in 638.