In the year A.D. 6 Moesia, which included a large part of the modern kingdom of Serbia and the northern half of that of Bulgaria between the Danube and the Balkan range (the classical Haemus), became an imperial province, and twenty years later Thrace, the country between the Balkan range and the Aegean, was incorporated in the empire, and was made a province by the Emperor Claudius in A.D. 46. The province of Illyricum or Dalmatia stretched between the Save and the Adriatic, and Pannonia lay between the Danube and the Save. In 107 A.D. the Emperor Trajan conquered the Dacians beyond the lower Danube, and organized a province of Dacia out of territory roughly equivalent to the modern Wallachia and Transylvania, This trans-Danubian territory did not remain attached to the empire for more than a hundred and fifty years; but within the river line a vast belt of country, stretching from the head of the Adriatic to the mouths of the Danube on the Black Sea, was Romanized through and through. The Emperor Trajan has been called the Charlemagne of the Balkan peninsula; all remains are attributed to him (he was nicknamed the Wallflower by Constantine the Great), and his reign marked the zenith of Roman power in this part of the world. The Balkan peninsula enjoyed the benefits of Roman civilization for three centuries, from the first to the fourth, but from the second century onwards the attitude of the Romans was defensive rather than offensive. The war against the Marcomanni under the Emperor Marcus Aurelius, in the second half of this century, was the turning-point. Rome was still victorious, but no territory was added to the empire. The third century saw the southward movement of the Germanic peoples, who took the place of the Celts. The Goths invaded the peninsula, and in 251 the Emperor Decius was killed in battle against them near Odessus on the Black Sea (the modern Varna). The Goths reached the outskirts of Thessalonica (Salonika), but were defeated by the Emperor Claudius at Naissus (Nish) in 269; shortly afterwards, however, the Emperor Aurelian had definitively to relinquish Dacia to them. The Emperor Diocletian, a native of Dalmatia, who reigned from 284 to 305, carried out a redistribution of the imperial provinces. Pannonia and western Illyria, or Dalmatia, were assigned to the prefecture of Italy, Thrace to that of the Orient, while the whole centre of the peninsula, from the Danube to the Peloponnese, constituted the prefecture of Illyria, with Thessalonica as capital. The territory to the north of the Danube having been lost, what is now western Bulgaria was renamed Dacia, while Moesia, the modern kingdom of Serbia, was made very much smaller. Praevalis, or the southern part of Dalmatia, approximately the modern Montenegro and Albania, was detached from that province and added to the prefecture of Illyria. In this way the boundary between the province of Dalmatia and the Balkan peninsula proper ran from near the