The Slavs come to the Balkans from a broad region in central and eastern Europe, which extended from the rivers Elbe in the west to the Dnieper in the east and from a point which touched the Carpathian mountains in the south and the river Niemen in the north.

Different tribes settle in different parts of the Balkan peninsula, subsequently developing their distinct identities.

The origin of the Croat tribe before the great migration of the Slavs is uncertain.

Most historians believe that the Croats are a purely Slavic people who probably migrated to the Balkans from the present-day Ukraine, but genetic evidence points indicates a high degree of merging with the pre-Slavic indigenous populations of the region of modern day Croatia.

A newer theory holds that the original Croats were nomadic Sarmatians who roamed Central Asia, migrated onto the steppes around 200 BCE, and rode into Europe near the end of the fourth century CE, possibly together with the Huns.

The Sarmatian Croats, the theory holds, conquered the Slavs of northern Bohemia and southern Poland and formed a small state called White Croatia near today's Kraków.

The Croats then supposedly mingled with their more numerous Slavic subjects and adopted the Slavic language, while the subjects assumed the tribal name "Croat."

The earliest mention of the Croatian name, Horoathos, can be traced on two stone inscriptions in Greek language and script, dating from around the year 200 CE, found in the seaport Tanais on the Azov sea, Crimea peninsula (near the Black Sea).

Both tablets are kept in the Archaeological museum in Saint Petersburg, Russia.

The Serbs, like the Croats, are believed by most scholars to be a purely Slavic people who originated in the Ukraine, though some now argue that both the original Serbs and Croats were Central Asian Sarmatian nomads who entered Europe with the Huns in the fourth century CE.

The theory proposes that the Sarmatian Serbs settled in a land designated as White Serbia, in what is now Saxony and Western Poland.

The Sarmatian Serbs, it is argued, intermarried with the indigenous Slavs of the region, adopted their language, and transferred their name to the Slavs.

The tribal designation Serboi first appears in the first century Geography of Ptolemy (book 5, 9.21) to designate a tribe dwelling in Sarmatia, probably on the Lower Volga River.

Subsidies have again failed to restrain the barbarians north of the Danube after the murder of Emperor Maurice in 602: the Danube fortification system is crushed, and waves of Slavic migrations become uncontrolled.

Together with the Avars, the Slavs break through the Danube frontier of the Roman Empire and occupy much of the Balkan Peninsula.

The Avar incursions prove key to the subsequent development of Yugoslavia because they immediately precede, and may have precipitated, the arrival of the precursor populations of the Slavic Serbs and Croats in the region.

Heraclius invites the Croats, a Slavic tribe living in Galicia, Silesia, and Bohemia, to settle in Illyricum.

They are given the land between the Drava River and the Adriatic Sea for the purpose of ridding the country of Avars.

The Serbs are allowed to move from their homeland north of the Carpathians to a territory east of the Croats.

Heraclius asks Pope Honorius I to send missionaries to both groups.

The Avars have never recovered from their failed assault on Constantinople.

As their empire crumbles, new peoples from the Black Sea to the Balkans have emerged to seize power: the Bulgars of Kubrat (Kuvrat), the Slavs under Samo, and the Serbs and Croats whom Heraclius had permitted to settle in the northwest Balkans once they had accepted Christianity.

Croats and Serbs settle during the seventh century in the lands that make up modern Bosnia and Herzegovina.

Western Southeast Europe (820 – 963 CE): Byzantine Greece, Slavic Principalities, and the Adriatic City-Ports

Geographic and Environmental Context

Western Southeast Europe includes Greece (outside Thrace), Albania, Montenegro, North Macedonia, Kosovo, most of Bosnia, southwestern Serbia, most of Croatia, and Slovenia.

• Coastal lowlands and islands along the Adriatic (Dalmatia, the Ionian isles) met the Dinaric and Pindus mountains’ karst and upland pastures.

• Interior corridors—Morava–Vardar, Drina–Sava, and the Via Egnatia from Dyrrachium (Durres) to Thessaloniki—linked the Aegean and Adriatic to the central Balkans.

• River valleys and Mediterranean basins of Attica, Boeotia, Peloponnese, and Epiros anchored Byzantine agrarian themes.

Climate and Environmental Shifts

• A Mediterranean–continental mix: wet winters and dry summers on the coasts; cooler, more variable regimes inland.

• Toward the 10th century, the onset of the Medieval Warm Period slightly lengthened growing seasons, aiding vine and olive culture in Greece and mixed cereal–pastoral economies inland.

Societies and Political Developments

• Byzantine Greece:

  • The empire reasserted control over earlier Slavic settlements (Sklaviniai) in Hellas and the Peloponnese, strengthening the Themes of Hellas and Peloponnēsos.

  • Under Basil I (867–886) and Leo VI (886–912), fort networks and fiscal-military administration recovered towns; Constantine VII (r. 913–959) codified provincial governance.

  • Monastic revival culminated at the end of the age with St. Athanasios founding the Great Lavra (963) on Mount Athos, inaugurating the Athonite commonwealth.

• Dalmatian coast & Adriatic cities (Split, Zadar, Trogir, Ragusa/Dubrovnik):

  • Urban municipalities under Byzantine suzerainty (with Latin civic traditions) acted as maritime hubs between Venice, southern Italy, and the Aegean; local comites and councils balanced imperial interests and city autonomy.

• Croatia:

  • The Duchy of Croatia consolidated in the 9th century; Christianity advanced under Frankish and papal influence.

  • Tomislav (traditionally crowned c. 925) forged a Kingdom of Croatia, mediating between Byzantium (Dalmatian cities) and the interior.

  • Glagolitic liturgy (from the missions of Cyril and Methodius) took root alongside the Latin rite.

• Serbian lands (Raška, Zahumlje, Travunija, Duklja/Dioclea):

  • The Vlastimirović dynasty (Serbia/Raška) and coastal principalities in Zahumlje (Herzegovina), Travunija, and Duklja (Montenegro) navigated between Byzantine, Bulgar, and later Croatian pressures.

  • Baptism and church-building progressed unevenly; župans governed district polities (župe) from hillforts (gradine).

• Bosnia & inland Slovenia:

  • Clustered hillfort communities under local župans and counts emerged along the Drina–Bosna–Vrbas and Sava corridors, tied to Croatian and Frankish spheres.

• North Macedonia & Kosovo:

  • Slavic communities in Macedonia and the Vardar basin faced alternating Byzantine and Bulgar influence; Thessaloniki remained the imperial anchor in the region.

  • The cultural afterglow of the Cyril–Methodius mission (863) radiated west via disciples and scriptoria.

Economy and Trade

• Agriculture:

  • Greece—olives, vines, wheat, and garden crops under village commons and monastic estates.

  • Uplands—transhumant flocks; lowlands—cereal rotations; coastal lagoons—salt and fish.

• Trade:

  • Via Egnatia moved Balkan grain, timber, and wax from Dyrrachium to Thessaloniki and Constantinople.

  • Adriatic shipping linked Dalmatian cities to Venice and Apulia; Byzantine nomismata and Italian denarii circulated with cloth, wine, ceramics, and metalware.

  • Interior market nodes (e.g., Skopje, Niš) exchanged hides, honey, wax, and slaves for Mediterranean goods.

Subsistence and Technology

• Terrace agriculture in Greek highlands; irrigation channels and cisterns in lowland plains.

• Pastoral transhumance across Dinaric and Pindus slopes; wool and hides fed urban workshops.

• Ship types: Byzantine dromōn and coastal transports; Dalmatian galleys and coasters; standardized amphorae and barrels for wine/oil.

• Fortifications: stone kastra along roads and passes; timber–earth hillforts (gradine) in inland Slavic zones.

• Scripts: Latin in the Adriatic cities; Greek in Byzantine administration; Glagolitic (later Cyrillic) permeated Slavic ecclesiastical use.

Movement and Interaction Corridors

• Via Egnatia: Dyrrachium–Thessaloniki–Constantinople, the main imperial artery.

• Morava–Vardar corridor: interior route from the middle Danube to the Aegean.

• Adriatic sea-lanes: Venice ⇄ Dalmatia ⇄ Greece; island chains served as stepping-stones.

• Mountain passes (e.g., Katara, Metsovo, Ivan): controlled troop movement and caravan traffic.

Belief and Symbolism

• Orthodox Christianity dominated Byzantine Greece; icons, relic cults, and monastic patronage shaped sacred geography (Athos, Meteora precursors).

• Latin Christianity prevailed in Dalmatian municipalities and among Croatian elites; rivalry and cooperation with Byzantium coexisted.

• Slavic Christianization advanced via Cyril–Methodius’ Slavic liturgy and local bishoprics; pagan survivals persisted in upland communities.

• Crosses on hillforts, basilicas in towns, and rural shrines marked the Christianization landscape.

Adaptation and Resilience

• Theme (provincial) systems mobilized local troops and taxes, enabling Byzantine Greece to weather raids and recover lands.

• Maritime redundancy—Adriatic and Aegean lanes—kept trade moving when inland conflict flared.

• Dual rites—Latin and Greek—reduced friction at the Adriatic–Aegean interface by embedding diplomacy in liturgy.

• Hillfort + kastron pairing allowed interior polities to buffer against Bulgar pushes and raiding.

Long-Term Significance

By 963 CE, Western Southeast Europe was a braided frontier:

• Byzantine Greece reestablished provincial depth and spiritual authority (Athos at the close of the age).

• Croatia crystallized into a kingdom, mediating Adriatic and inland interests.

• Serbian principalities and Macedonian Slavs balanced between Bulgaria and Byzantium.

• Dalmatian cities prospered as Adriatic brokers under imperial suzerainty.
  These dynamics set the stage for the Bulgar–Byzantine wars of the next age, the Adriatic rise of Venice, and the maturation of Slavic Christian polities across the western Balkans.

Most historians believe that the Croats are a purely Slavic people who probably migrated to the Balkans from present-day Ukraine.

A newer theory, however, holds that the original Croats were nomadic Sarmatians who roamed Central Asia, migrated onto the steppes around 200 BCE, and rode into Europe near the end of the fourth century CE, possibly together with the Huns.

The Sarmatian Croats, the theory holds, conquered the Slavs of northern Bohemia and southern Poland and formed a small state called White Croatia near present-day Kraków.

The Croats then supposedly mingled with their more numerous Slavic subjects and adopted the Slavic language, while the subjects assumed the tribal name "Croat."

A tenth-century Byzantine source reports that in the seventh century Emperor Heraclius enlisted the Croats to expel the Avars from Byzantine lands.

The Croats had overrun the Avars and Slavs in Dalmatia around 630, then drove the Avars from today's Slovenia and other areas.

In the eighth century, the Croats lived under loose imperial rule, and Christianity and Latin culture recovered in the coastal cities.

The Franks subjugated most of the Croats in the eighth century and sent missionaries to baptize them in the Latin rite, but the Byzantine Empire continued to rule Dalmatia.

Croatia emerges as an independent nation in 924.

Tomislav (910-ca. 928), a tribal leader, establishes himself as the first king of Croatia, ruling a domain that stretches eastward to the Danube.

Like the Croats, the Serbs are believed to be a purely Slavic people who originated in Ukraine.

Some scholars now argue that the original Serbs were Central Asian Sarmatian nomads who en\tered Europe with the Huns in the fourth century CE.

The theory proposes that the Sarmatian Serbs settled in a land designated as White Serbia, in what is now Saxony and western Poland.

The Sarmatian Serbs, it is argued, intermarried with the indigenous Slavs of the region, adopted their language, and transferred their name to the Slavs.

Byzantine sources report that some Serbs migrated southward in the seventh century CE and eventually settled in the lands that now make up southern Serbia, Montenegro, Kosovo, and Bosnia and Hercegovina.

Rival chiefs, or zupani, vie to control the Serbs for five centuries after the migration.

Zupan Vlastimir forms a Serbian principality under the East Roman Empire around 850, and the Serbs soon convert to Eastern-rite Christianity.

The many tribes—Danes, Obotrites, Slovenes, Bretons, Basques—that inhabit the frontier lands at the start of the reign of Louis the German over Eastern Francia had remained in awe at the power of the Frankish emperor and dared not stir up any trouble.

The Sorbs in 818 had rebelled, however, and had been quickly followed by Slavomir, chief of the Obotrites, who had been captured and abandoned by his own people, being replaced in 818 by Ceadrag.

Soon, Ceadrag too had turned against the Franks and allied with the Danes, who will shortly become the greatest menace of the Franks.

A greater Slavic menace is gathering on the southeast, where, Ljudevit Posavski, the Croat Prince of Savia from about 810, is harassing the border at the Drava and Sava rivers.

As the ruler of the Pannonian Croats, his successful resistance of Frankish domination is an important precursor to the eventual unification of Croatian duchies in Dalmatia and Pannonia into the Kingdom of Croatia.

The margrave of Friuli, Cadolah, had been sent out against him, but he had died on campaign and in 820 his margarvate had been invaded by Slovenes.

An alliance had been made in 821 with Borna, duke of Dalmatia, and in 822 Ljudevit is brought to heel.

After being forced to flee, Ljudevit becomes a ruler over the Serbs, maintaining close ties with the Carantanians and Timokians (the Slavs, or Vlachs, in the Timok River valley).