Southeast Europe (909 BCE – 819 CE): Iron Kingdoms, Roman Frontiers, and Byzantine Beginnings

Regional Overview

Between the Adriatic and the Black Sea, Southeast Europe stood for a millennium as the hinge between the Mediterranean world and the steppe.
Its twin landscapes—the eastern Danubian–Thracian plains and the western Adriatic–Illyrian mountains—produced parallel yet intertwined histories.
Both absorbed Hellenic colonization, entered the Roman orbit, and later weathered the migrations that forged medieval Europe.
The region’s story from the early Iron Age to late Antiquity is thus one of fusion and frontier, where Greek, Roman, Thracian, Illyrian, and Slavic worlds met and reshaped one another.

Geography and Environment

The region divides naturally:

• Eastern Southeast Europe embraces the Lower Danube, Thracian plain, and Black Sea coast, enclosed by the Balkan and Carpathian arcs. Fertile lowlands sustained dense agrarian settlement, while the Danube served as both artery and barrier.

• Western Southeast Europe rises into karstic uplands and Adriatic coasts, with sheltered island chains and mountain basins suited to mixed farming and seaborne trade.

Climatic variation—humid along the coasts, continental inland—produced complementary economies: grain, salt, and metals from the east; timber, livestock, and maritime goods from the west.
Seasonal river floods and Adriatic storms shaped transport calendars; alpine passes and sea lanes linked every valley to the wider Mediterranean.

Societies and Political Developments

Greek Colonies and Indigenous Kingdoms

From the 8th to 5th centuries BCE, Greek settlers established poleis along both coasts: Apollonia and Dyrrhachium on the Adriatic; Odessos, Mesambria, and Histria on the Black Sea.
Behind them, Illyrian, Thracian, and Geto-Dacian tribes forged early kingdoms—the Odrysian realm in Thrace, the Ardiaean and Dardanian dominions in the west.
These polities traded metals, grain, and slaves for imported wine, oil, and ceramics, mediating between the Mediterranean and the interior.

Rome and the Imperial Frontier

Between the 2nd century BCE and the 1st century CE, Rome absorbed the entire peninsula: Macedonia, Illyricum, Dalmatia, Moesia, Thrace, and briefly Dacia north of the Danube.
Roman roads—the Via Egnatia, Via Militaris, and Sava-Drava corridors—stitched the provinces together.
Urban centers such as Salona, Skupi, Nicomedia, and Serdica reflected Roman law and architecture, while legionary camps and bridgeheads (Apollodorus’ bridge at Drobeta) turned the Danube into the empire’s longest fortified line.
Mining in Dacia, shipyards on the Adriatic, and grain estates in Moesia underpinned prosperity until the 3rd-century crises.

Migrations and the Byzantine Transition

From the 3rd to 7th centuries CE, the frontier dissolved under waves of Goths, Huns, Avars, and Slavs.
Cities were sacked, repopulated, and repurposed as Byzantine forts.
The Eastern Roman Empire, centered on Constantinople, re-emerged as the stabilizing power, holding Thrace and the coastal Adriatic while fostering Christianization.
By the late 7th century, the First Bulgarian Empire rose in Moesia and Thrace; Croatian and Serbian principalities took form in the western mountains, bridging the late antique and medieval orders.

Economy and Exchange

Agriculture remained the foundation:

• The Thracian plain and Wallachian lowlands exported grain and livestock along the Danube.

• The Adriatic coasts specialized in wine, oil, salted fish, and amphora industries.

• Mining of gold, silver, and iron in Dacia and the western ranges enriched both local chieftains and Roman prefects.

Trade routes—riverine, overland, and maritime—made the region a corridor between the Aegean, the Pannonian plain, and the steppe.
After Rome’s decline, Byzantine and Bulgar administrations preserved key arteries, ensuring continuity of commerce despite political fragmentation.

Technology and Material Culture

Iron metallurgy and Roman engineering reshaped daily life.
Stone bridges, aqueducts, and bath complexes signaled urban sophistication; rural estates used the iron plow to expand cultivation.
Local craftsmanship persisted: Thracian and Illyrian metalwork, Dacian goldsmithing, and later Slavic wood and textile arts.
Christian churches and monasteries, often rising atop pagan sanctuaries, announced new spiritual geographies while reusing classical masonry.

Belief and Symbolism

Religious life reflected the region’s pluralism:

• Indigenous cults—Zalmoxis, the Thracian Horseman—coexisted with Greek polytheism and Roman state worship.

• Christianity spread from urban bishoprics by the 4th century CE, producing early saints and councils.

• Slavic and Bulgar paganisms, with sky- and ancestor-deities, persisted until conversion in the 8th–9th centuries.
  Thus the region became a spiritual palimpsest, each new faith overlaying rather than erasing the old.

Adaptation and Resilience

Southeast Europe’s resilience lay in its geographical layering: river corridors, mountain refuges, and island coasts offered fallback zones in war or climate stress.
Agro-pastoral economies allowed mobility; fortified towns and hillforts provided refuge during invasions.
Byzantine fiscal systems and Bulgar tribute networks recycled Roman infrastructures, ensuring survival of settlement and trade patterns despite continual upheaval.

Regional Synthesis and Long-Term Significance

By 819 CE, Southeast Europe had completed its ancient cycle.
In the east, Byzantine Thrace and the Bulgar kingdom defined a Christian–steppe frontier along the Danube.
In the west, Slavic kingdoms grew amid the ruins of Roman Dalmatia, while the Adriatic cities preserved classical urbanism under imperial and papal influence.
Greek colonies, Roman provinces, and barbarian migrations had fused into a single cultural continuum—one that naturally divides into eastern (Danubian–Thracian) and western (Adriatic–Illyrian) spheres yet remains bound by geography, trade, and faith.

This equilibrium of coast and hinterland, empire and tribe, set the pattern for the medieval Balkans: a region perpetually contested but never peripheral, mediating between the Mediterranean world and the steppes beyond.

Eastern Southeast Europe (909 BCE – 819 CE) Early Iron & Antiquity — Greek Poleis, Thracians & Dacians, Rome & Byzantium, Migrations and Bulgars

Geographic and Environmental Context

Eastern Southeast Europe includes Turkey-in-Europe (Thrace); Greece’s Thrace; Bulgaria (except its southwest); Romania & Moldova; northeastern Serbia; northeastern Croatia; extreme northeastern Bosnia & Herzegovina.

• Anchors: Greek Black Sea poleis (Histria, Tomis/Constanța, Callatis/Mangalia, Odessos/Varna, Mesambria/Nessebar, Apollonia/Sozopol), Thrace (Odrysian kingdom), Moesia (Danube limes), Dacia(Transylvania & Wallachia), Lower Danube legionary line, Carpathian–Balkan passes.

Climate & Environmental Shifts

• First-millennium variability; fertile Thracian and Wallachian plains supported dense settlement; Danube avulsions required continual river management.

Societies & Political Developments

• Greek colonies flourished (7th–5th c. BCE) along the western Black Sea.

• Thracian Odrysian kingdom (5th–4th c. BCE) and Geto-Dacians north of the Danube rose to prominence.

• Rome annexed Moesia and Thrace; Dacia (106–271 CE) north of the Danube briefly Romanized with cities, mines, roads; Danube limes fortified.

• Migrations: Goths (3rd–4th c.), Huns (5th c.), Avars and Slavs (6th–7th c.) reconfigured the region;

• First Bulgarian Empire (from 681 CE) entrenched in Moesia/Thrace; Byzantium held Thrace and coastal cities.

Economy & Trade

• Grain, wine, salt, and livestock moved along the Danube; Black Sea ports exported to the Aegean–Mediterranean; mining (gold/silver in Dacia, iron in Thrace).

• Roman urbanism (roads, bridges e.g., Apollodorus’ bridge near Drobeta) integrated the frontier.

Technology & Material Culture

• Iron plowshares; Roman engineering; Thracian/Dacian metalwork; Byzantine fortifications.

• Urban mosaics, inscriptions, temples; later churches and monasteries.

Belief & Symbolism

• Thracian and Dacian cults (horseman, Zalmoxis); Greek polytheism; Roman state cults → Christianity (by late Roman/Byzantine era).

• Early Slavic and Bulgar paganisms persisted into 8th–9th c., gradually Christianizing.

Environmental Adaptation & Resilience

• Riverine transport and oasis agriculture stabilized supply; fortified towns and hillforts provided refuge; steppe pastoralism remained flexible under aridity pulses.

Legacy & Transition

By 819 CE, Eastern Southeast Europe was a braided frontier of Byzantine Thrace, Bulgar power, Slavic communities, and legacy Roman–Greek Black Sea cities. The Lower Danube’s fortified line, Thracian plain granaries, and coastal emporia formed the scaffolding for the medieval dynamics to come.

The Growth of Christianity in the Roman Empire and Its Relationship with Judaism

During the early centuries of the Common Era, Christianity gradually gained a foothold in the Roman Empire, evolving from a small sect of Judaism into a distinct religious movement. As Christianity spread, its leaders sought to establish a universal message that appealed to a wider audience beyond the Jewish community.

Christianity’s Interpretation of the Hebrew Bible

• Early Christian theologians reinterpreted the Hebrew Bible (which they termed the “Old Testament”) as a precursor to the New Testament, claiming that:

  • The laws and prophecies of the Old Testament were fulfilled through Jesus Christ.
  • Christian believers—both Jews and Gentiles—represented the new Israel, spiritually and physically.

• This reinterpretation positioned Christianity as the continuation and fulfillment of Jewish tradition, differentiating it from Judaism, which maintained its adherence to Mosaic Law and awaited a different messianic fulfillment.

Christian Views on Jewish Exile and Survival

• Many early Christians interpreted the Jewish exile as a divine punishment, believing it was a consequence of:

  • The Jews’ rejection of Jesus as the Messiah.
  • Their perceived role in his crucifixion, an accusation that contributed to Christian anti-Judaism in later centuries.

• At the same time, the continued survival of Judaism, despite exile and persecution, puzzled many early Christians.

  • Some saw Jewish endurance as stubborn defiance of divine will.
  • Others, such as Augustine of Hippo, later argued that the Jewish people were preserved by God as “witnesses” to the validity of Christian prophecy, even in their dispersion.

Impact on Christian-Jewish Relations

• As Christianity became the dominant religion of the Roman Empire, tensions with Jewish communities intensified.

• Christian leaders sought to differentiate their faith from Judaism, leading to:

  • Theological disputes over the interpretation of scripture.
  • Legal restrictions on Jewish practices under Christianized Roman rule.
  • The development of Christian supersessionism, the belief that Christianity had replaced Judaism in God’s covenant.

• Despite opposition, Judaism survived and continued to develop, leading to a complex and often strained relationship between the two religious traditions throughout Late Antiquity and the Middle Ages.

Conclusion: Christianity’s Rise and Its Effects on Jewish Identity

The early growth of Christianity in the Roman Empire involved reinterpretations of Jewish scripture, shaping its self-identity as the “new Israel”. However, Jewish persistence despite exile challenged Christian theological narratives, leading to centuries of debate, tension, and periodic persecution. This dynamic profoundly influenced religious thought and interfaith relations throughout history.

Constantine's conversion to Christianity brings a new era of prosperity to Palestine, which attracts a flood of pilgrims from all over the empire.

As a geographic unit, Palestine extends from the Mediterranean on the west to the Arabian Desert on the east and from the lower Litani River in the north to the Gaza Valley in the south.

Named after the Philistines, who occupied the southern coastal region in the twelfth century BCE, the name Philistia was used in the second century CE to designate Syria Palestina, which formed the southern third of the Roman province of Syria.

The Crisis and Revival of Roman Gaul (250s–Early 4th Century CE)

1. The Crisis of Roman Gaul (250s–280s CE)

During the mid-3rd century CE, Roman Gaul faced a period of severe instability, coinciding with the broader Crisis of the Third Century (235–284 CE).

• Barbarian Invasions:

  • The Franks, Alemanni, and Vandals launched multiple incursions across the Rhine frontier, sacking cities and disrupting trade.
  • The Goths and other Germanic groups added further pressure on Rome’s borders.

• Political Instability:

  • The collapse of central authority led to usurpations and local rebellions.
  • In 260 CE, Postumus, a Roman general, declared the Gallic Empire, breaking away from Rome and ruling Gaul, Britain, and parts of Spain until 274 CE, when Emperor Aurelian reconquered the region.

• Economic Decline:

  • The destruction of cities and trade networks led to widespread economic hardship.
  • The debasement of Roman currency and rising taxation further weakened the Gallic economy.

2. The Revival of Roman Gaul (Early 4th Century CE)

The situation improved significantly in the early 4th century CE, as a period of recovery and prosperity took hold.

• The Tetrarchy and Constantine’s Reforms:

  • Diocletian (r. 284–305 CE) restructured the empire, restoring order and military strength.
  • Constantine I (r. 306–337 CE) further stabilized the region, reinforcing defenses along the Rhine and establishing new military bases.

• Economic Recovery:

  • With barbarian invasions subdued, trade and agriculture flourished again.
  • Cities such as Treverorum (modern Trier) became imperial residences, reinforcing Roman authority in the West.

• Rise of Christianity:

  • Until 312 CE, Christians had faced periodic persecution, particularly under emperors like Diocletian.
  • After Constantine’s conversion in 312 CE, Christianity spread rapidly across Gaul and the empire, reshaping its cultural and religious landscape.
  • Major cities, including Lugdunum (Lyon), Treverorum (Trier), and Arelate (Arles), became key Christian centers.

Conclusion: A Period of Transformation

The 250s–280s CE marked a time of crisis in Roman Gaul, with barbarian invasions, political fragmentation, and economic decline threatening the region. However, in the early 4th century CE, reforms under Diocletian and Constantine I brought a revival, leading to a resurgence of prosperity and the rapid spread of Christianity, setting the stage for the Christianization of the empire and the transformation of Late Antiquity.

The End of Christian Persecution and the Reforms of Constantine (311–313 CE)

By the early 4th century CE, the Roman Empire witnessed a major shift in religious policy. After decades of Christian persecution under Diocletian (303–311 CE), Emperor Galerius officially ended the repression of Christians in 311 CE, signaling a significant turning point in imperial attitudes toward Christianity.

1. The Edict of Toleration (311 CE) and the End of Persecution

• Galerius, once a strong opponent of Christianity, issued an edict of toleration, acknowledging that:
  • The persecution of Christians had failed to eradicate the faith.
  • Christianity should be tolerated, provided its followers prayed for the empire’s well-being.
• While this edict ended official state persecution, it did not fully legalize Christianity.

2. The Edict of Milan (313 CE) and the Full Legalization of Christianity

• Two years later, in 313 CE, Constantine the Great and Licinius issued the Edict of Milan, which:
  • Granted Christians full legal status in the Roman Empire.
  • Guaranteed religious tolerance for all faiths.
  • Restored confiscated Christian properties, further legitimizing the Church.
• The Edict of Milan marked a decisive shift in imperial policy, paving the way for Christianity to become deeply intertwined with Roman governance.

3. Constantine’s Gradual Personal Conversion

• While Constantine became a protector of Christianity, his personal conversion unfolded gradually:
  • He continued to patronize both Christian and pagan traditions, maintaining political flexibility.
  • His famous vision of the Cross before the Battle of the Milvian Bridge (312 CE) strengthened his faith in Christianity.
  • He was only baptized on his deathbed in 337 CE, reflecting a slow transformation rather than an abrupt conversion.

4. The Reforms of Diocletian and Constantine: Temporary Stability, Long-Term Challenges

The combined reforms of Diocletian and Constantine temporarily strengthened the Roman Empire by:

• Reorganizing the administration through the Tetrarchy and later centralized rule.
• Reforming the military, reinforcing the empire’s defensive capabilities.
• Stabilizing the economy, although Constantine’s introduction of the solidus (gold coin) had mixed long-term effects.

However, despite these efforts, chronic governance challenges persisted, including:

• Internal power struggles, leading to civil wars even after Constantine’s reign.
• Frontier pressures, as Germanic and Persian threats continued.
• Economic difficulties, as taxation and inflation weakened Rome’s financial stability.

5. Conclusion: The Transition to a Christian Empire and the Road Ahead

• The legalization of Christianity marked the beginning of a new era, leading to its eventual status as the official state religion under Theodosius I (381 CE).
• Constantine’s reforms prolonged the empire’s survival, but deep-seated issues remained, foreshadowing the eventual decline of the Western Roman Empire in the 5th century.

Though imperial stability was temporarily restored, the challenges faced by Rome would continue to evolve, shaping the empire’s fate in the centuries to come.

The Arian Controversy and Its Impact on Early Christianity (325–381 CE)

The Arian Controversy was a prolonged theological dispute within early Christianity, primarily concerning Christology, or the nature of the relationship between God the Father and Jesus Christ the Son. This debate divided the Christian Church for over half a century, beginning before the Council of Nicaea (325 CE) and continuing until after the Council of Constantinople (381 CE).

1. The Core Issue: The Nature of Christ

• The controversy arose from conflicting interpretations of Jesus’ divinity and his relationship to God the Father.
• Arius, a Christian priest and theologian in Alexandria, argued that:
  • Christ was created by God and did not share the same eternal nature as God the Father.
  • The Son was "begotten" before time but was not co-eternal with the Father.
  • His famous phrase: "There was a time when the Son was not."
• Athanasius, the Catholic bishop of Alexandria and later a Church Father, opposed this view, insisting that:
  • Christ was of the same substance (homoousios) as the Father.
  • The Son was eternal, divine, and equal to God.

2. The Council of Nicaea (325 CE): Condemnation of Arianism

• Emperor Constantine convened the First Council of Nicaea in 325 CE to resolve the dispute and unify the Church.
• The Council ruled against Arianism, affirming that:
  • Christ is "begotten, not made" and is homoousios ("of the same substance") as the Father.
  • The Nicene Creed was formulated, establishing orthodox Christian belief.
• However, Arianism persisted, especially in the eastern provinces of the empire, where many bishops remained sympathetic to Arius’ teachings.

3. Continued Conflict and the Council of Constantinople (381 CE)

• Despite Nicaea’s ruling, Arianism remained influential, with several emperors, including Constantius II (r. 337–361 CE), supporting it.
• Athanasius and other Nicene leaders were repeatedly exiled during the 4th century.
• The controversy was finally addressed again at the Council of Constantinople (381 CE), where:
  • The Nicene Creed was reaffirmed and expanded.
  • Arianism was officially condemned as heresy.
  • The doctrine of the Holy Trinity was further clarified, establishing the basis for Christian orthodoxy.

4. Legacy of the Arian Controversy

• Shaped Christian doctrine – The debates led to clearer definitions of Christ’s divine nature, influencing Christian theology for centuries.
• Divided the Church and the Empire – The controversy fueled political and religious divisions, with emperors and bishops taking sides.
• Spread of Arian Christianity – Though condemned, Arianism remained influential among Germanic tribes (e.g., Visigoths, Ostrogoths, and Vandals) into the early medieval period.

The Arian Controversy fundamentally shaped early Christian doctrine, with its resolution at Constantinople in 381 CE marking the triumph of Nicene orthodoxy and laying the foundation for Trinitarian Christianity as the dominant belief system within the Catholic Church and later Christendom.

One Athanasius, who seems to have been brought early in life under the immediate supervision of the ecclesiastical authorities of his native Alexandria, is educated classically and theologically here and ordained deacon and appointed secretary to Bishop Alexander.

Here, in the intellectual, moral, and political center of the ethnically diverse Greco-Roman world, he articulates in around 318 the orthodox doctrine of redemption in an early work, On the Incarnation of the Word.

A  presbyter named Arius comes into a direct conflict in about 319, with Alexander.

Arius appears to have approached Alexander for what he felt were misguided or heretical teachings being taught by the bishop.

Arius’ theological views appear to have been firmly rooted in Alexandrian Christianity, and his Christological views are certainly not at all radical.

He embraces a subordinationist Christology (that God did not have a beginning, but the Logos did), heavily influenced by Alexandrian thinkers like Origen, which is a common Christological view in Alexandria at this time.

Arius, in essence, denies the full deity of the preexistent Son of God who became incarnate in Jesus Christ.

He argues that God created the Son, while divine and like God ("of like substance"), as the agent through whom he created the universe.

Says Arius of the Son: "there was a time when he was not."

The Arianist creed as propounded by Arius holds that Christ, as the begotten Son of God, was created as other humans and that only the unbegotten God the Father is divine.

Constantine, now sole emperor of East and West, had in 324 made Byzantium the official capital of Roman Empire.

(There is no evidence that the city’s title of Nova Roma, or New Rome, was actually used for official purposes in Constantine's own time).

By this time, Constantine, who has on several occasions granted special privileges to individual churches and bishops, now openly embraces Christianity.

Constantine, after his victory over Licinius in 324, writes that he has come from the farthest shores of Britain as God's chosen instrument for the suppression of impiety, and in a letter to the Persian king Shapur II he proclaims that, aided by the divine power of God, he has come to bring peace and prosperity to all lands.

The Arian heresy, with its intricate explorations of the precise nature of the Trinity that are couched in difficult Greek, is as remote from Constantine's educational background as it is from his impatient, urgent temperament.

In a letter to the chief protagonist, Arius of Alexandria, Constantine states his opinion that the dispute had been fostered only by excessive leisure and academic contention, that the point at issue is trivial and can be resolved without difficulty.