The Balkans is the recent geographic name used to describe a region of southeastern Europe. The region has a combined area of 550,000 km² and an approximate population of 55 million people. The classical Greek name for the actual Balkan Peninsula was the Peninsula of Haemus or Χερσόνησος του 'Αίμου (ancient Chersónesos tou Haimou, or in modern Greek Chersónisos tou Aímou). The region takes its Turkish name from the newer Balkan Mountains (ancient Chaemos oros), which run through the centre of Bulgaria into eastern Serbia.
Possibly the best-known parts of the Balkans, in history, are the loosely knit free states and city states of the Greeks; Macedonia rising to its period of conquests under Alexander the Great in the sixth century BC. The Greeks had planted colonies along the Balkan shores and their merchants also set out inland with their influence. The Greeks, however, had never succeeded in reducing the barbarians living on the slopes of the Rhodope and Balkan mountains to any kind of political dependence. This area's vigor oozed away and, when, in the second century BC, it fell before the advance of Rome, the first or Greek phase of early Balkan history came to a close. The Balkans were conquered by Rome and it was left to them to achieve the political fusion of this area. In 328AD the Roman Emperor Constantine I established a new capital on the site of the ancient Greek trading post of Byzantium, naming the new foundation Constantinople.
The Macedonians who held the region north of Thessaly were the southernmost tribe of Thracians and gradually they fell under Greek influence. In 197 BC and 168 BC the Romans totally defeated and conquered Macedonia. Beyond Macedonia the Thracian and Illyrian primitive tribes dominated the Balkans. Sometime before 200BC the Romans had also begun to clash with the Illyrian pirate state along the east coast of the Adriatic Sea. Numerous campaigns brought all of the Balkans under Roman rule by the reign of the first Emperor, Augustus. They constructed a network of paved highways and established military garrisons along their course as a guarantee of public order. The most notable of these highways was the via Egnatia which started at Dyrrachium (Durazzo). With the exception of today's Croatia (but not its coast) virtually all of the former country of Yugoslavia became part of the Roman province of Illyria or Illyricum, under its own governor. Adrianople, Philippopolis, Sofia, Nish and Belgrade were all cities of Roman foundation. With Roman law came certain stability and peddlers from Italy and other Mediterranean centres with their wares streamed into the region and settled down as local merchants. Just as Macedonia had become Hellenised the region now became Romanised. The Thracian dialect gradually disappeared entirely, whilst in pockets the Illyrian language continued to maintain itself. Illyria in particular became a favourite place for soldiers to be given land grants as farms upon their retirement. In the year 212 AD the Emperor Caracalla granted Roman citizenship to all free men throughout the Empire and this included the Balkans.
However, during the later Roman era began the great migrations from the north into this area. Numerous tribes, Teutons and Slavs, set themselves in motion towards the warm south from the inhospitable north, their only principle obstacles being the rivers Rhine and the Danube, which the Romans had organised as natural lines of defence. This became a great headache for the governments at Rome and, later, Constantinople, who, in the latter's sphere, gradually found themselves threatened by the advances of Slavs, Tartars, and, ultimately, Turks.
The South Slavs, having drifted into the Balkans in scores of disassociated tribes, consolidated, as a result of geography and over the course of time, into four distinct and recogiseable groups: the Slovenes, the Croats, the Serbs and the Bulgars. The Slovenes occupied their lands at the head of the Adriatic including the southern and eastern slopes of the Austrian Alps and are the westernmost group. East and south-east of the Slovenes, between the river Drave and the Adriatic Sea, are the Croats (includes Istria). East and southeast of the Croats the Serbs are scattered over a wide area between the Danube and the Adriatic. They occupy the heart of the peninsular and are considered an out-and-out Balkan people. The Slovenes and Croats eventually becoming Christianised by western missionaries adopted the civilisation from the great western hearth of faith, from Rome. As Catholics they thereby became separated in fundamental ways of thought from the Serbs, who, from the ninth century, were Christianised by the Orthodox missionaries of the Eastern Roman Empire, and looked to Constantinople. The greatest sufferers of this Slav migration were the Roman Latin-speaking provincials, for it was their territory which the Slavs had seized. 
There is very considerable debate about the penetration of the migrating Slavs into Bulgaria. Schevill, the great Balkan expert, states that "occasionally Slav tribes penetrated into Thessaly, while others reached the Peloponnesus and took over and settled a considerable area of Greek soil." By this he means Byzantine lands. Greek nationalists argue much about this migration and settlement. How far Slavs penetrated into what is now Bulgaria is unclear, but it is known that as early as the seventh century the Bulgars (said to be related to the Huns and Avars) arrived from the distant region of Kazan and conquered those lands now named after them, driving out the Greek presence and absorbing those Slav tribes already in Bulgaria for a century, using them as serfs.
- Schevill, Ferdinand, A History of the Balkans - from the Earliest Times, 1922, republished by Barnes & Noble, USA, 1995, p.14 and notes. ISBN 0-88029-697-6
- Schevill, 1922/1995, p.5-6.
- Schevill, 1922/1995, p.27-8.
- Mommsen, Theodor, translated by Professor Wm. P.Dickson, D.D.,LL.D., The Provinces of the Roman Empire, 1885/revised 1909/republished 1996, p.21, ISBN 0-76070-145-8.
- Schevill, 1922/1995, p.26-32.
- Schevill, 1922/1995, p.7-9.
- Schevill, 1922/1995, pps:72, 77-8 and 141-2.
- Schevill, 1922/1995, pps:77-8 and 92.