With Harun al-Rashid's accession in 786, the raids launched over the next two years were relatively minor affairs; the first great invasion of the new reign occurred in 788, when a large expeditionary force crossed the Cilician Gates into the Anatolic Theme. Although the raid is not mentioned in Arabic sources, its description by the Byzantine chronicler Theophanes the Confessor points to a major invasion, as it was confronted by the forces of the two most powerful Byzantine thematic armies, those of the Anatolic Theme itself and of the Opsician Theme.