 Complete the following phrase:  Gennadius remained in Africa as magister militum for a long time until the early 590s, and it was he who became the first exarchus of Africa, when Emperor Maurice established the exarchate in the late 580s, uniting civil and military authority in his hands. The exarchate extended over North Africa, the imperial possessions in Spain, the Balearic Islands, Sardinia, and Corsica. It prospered greatly, and under Heraclius, African forces overthrew the tyrant Phocas in 610. The exarchate was a practically autonomous entity from the 640s on, and survived until the 