The original Roman Senate continued to express decrees into the late 6th century, and the last Eastern Roman emperor to use Latin as the language of his court in Constantinople was emperor Maurice, who reigned until 602. The overthrow of Maurice by his mutinying Danube army under Phocas resulted in the Slavic invasion of the Balkans and the decline of Balkan and Greek urban culture (leading to the flight of Balkan Latin speakers to the mountains, see Origin of the Romanians), and also provoked the Byzantine–Sasanian War of 602–628 in which all the great eastern cities except Constantinople were lost. The resulting turmoil did not end until the Muslim conquests of the 7th century finalized the irreversible loss of all the largest Eastern Roman imperial cities besides the capital itself. The emperor Heraclius in Constantinople, who emerged during this period, conducted his court in Greek, not Latin, though Greek had always been an administrative language of the eastern Roman regions. Eastern-Western links weakened with the ending of the Byzantine Papacy.