Byzantine history initially represents just a new era of Roman history. However, a transformation process soon begins, leading from the old Roman Empire to the development of a distinct Byzantine state. The structural elements and driving forces of this change are the administration of the empire, Greek culture, and the Christian faith. Through their interaction, a new high culture emerges that lasts for over a thousand years and remains superior to all contemporary cultural achievements of the West until the High Middle Ages. However, this period of intellectual and artistic flourishing is accompanied by a decline in imperial power. The Byzantine state is repeatedly challenged militarily. The attackers include Persians and Avars, Arabs and Bulgarians; however, during these wars, territorial losses must be accepted.