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
lake of Scutari in the south to the river Drinus (the modern Drina), whose
course it followed till the Save was reached in the north.

An event of far-reaching importance in the following century was the
elevation by Constantine the Great of the Greek colony of Byzantium into
the imperial city of Constantinople in 325. This century also witnessed