Irene of Athens
In 782, the Abbasid Caliph's son, Harun al-Rashid (Caliph in 786–809), campaigned against the Byzantine Empire and invaded Asia Minor. The Byzantines, under the eunuch logothete Staurakios, managed to cut off Harun's return and encircle his army. Tatzates chose this moment to defect to Harun with many of his men. His defection, however, was kept secret for a while, allowing Harun to seize the Byzantine envoys, Staurakios among them, who had come to negotiate a truce. The Abbasid commander was thus able to dictate harsh terms to Empress-regent Irene of Athens.