In this rivalry the Servians secured the greatest prizes in the way of territorial expansion. By the end of the thirteenth century they had reached the sea coast, and had occupied the region around the two lakes Ochrida and Prespa. About the same time the movement to expand their frontiers at the expense of the Greek Empire again became marked. Northern Albania was conquered and additional lands were seized in Macedonia. These successes led to a coalition between the Bulgars and the Greeks; but this scheme to block the Servians failed. There was a great battle at Velbouje, at which the Bulgarian army was completely crushed. The plan of the Servians was to secure the alliance of their rivals by a marriage between their leader, Stephen Douchan, and the sister of Tsar Michael, the head of the Bulgars. Douchan is often called the Charlemagne of Servia, but the title is only true if measured by an unrealized dream. His reign marks the limit of Servian ambition; he looked forward to an imperial position under which the Slavs would become the heirs of the dignities and domains of the Byzantine Empire, a position they deserved because of the inability of the Greeks to defend their lands from the advancing power of the Turk. For a time the dream seemed on the point of realization, as Douchan’s various campaigns against the Greeks were successful. The alliance with the Bulgars was maintained unbroken, and only a very small part of the European possessions of the Emperors at Constantinople remained intact. Thrace and a strip of Asia Minor was all that was left; there was every reason to urge Douchan to proclaim his overlordship in the regular way. Accordingly, on April 16, 1346, Douchan was solemnly anointed Emperor (Tsar) of Servia and Roumania by the Servian Patriarch Joannikos, at Uskup. The next step was the conquest of the imperial city on the Bosphorus. This could not be effected without a fleet; neither Thessalonika nor Constantinople could be taken as long as their ports were open. Douchan turned to the Venetians for help, but they refused to encourage the formation of a new great power on the Mediterranean. Besides, the Turks now barred the way, for Gallipoli had been garrisoned. The Osmanlis, therefore, held the key to the Dardanelles. Undeterred, however, by these changes, Douchan girded himself for a final attack on Constantinople, when death overtook him suddenly on the 20th of December, 1355.