Dalmatia first came under Byzantine control in the 530s, when the generals of Emperor Justinian I (r. 527–565) seized it from the Ostrogoths in the Gothic War. The invasions of the Avars and Slavs in the 7th century destroyed the main cities and overran much of the hinterland, with Byzantine control limited to the islands and certain new coastal cities such as Split and Dubrovnik, while Zara (Zadar) became the local episcopal and administrative center, under an archon.