 In mid-June 838, Afshin crossed the Anti-Taurus Mountains and encamped at the fort of Dazimon, between Amaseia and Tokate, a strategically important location which the Byzantines also used as a forward staging area.A few days later, on 19 June, the vanguard of the main Abbasid army also invaded Byzantine territory, followed two days after by the Caliph with the main body.Emperor Theophilos chose to confront Afshin first, since although his army was smaller, it threatened to cut off his supply lines.