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.

Magnentius' Rise to Power and the Overthrow of Constans (350 CE)

Magnus Magnentius, a pagan of German descent, was born in Samarobriva (modern Amiens, Gaul) and rose to prominence as a distinguished soldier. By 350 CE, he commanded the Herculians and Iovians, two elite imperial guard units, giving him significant military influence (Zosimus, ii.58).

1. Growing Discontent with Constans

• Emperor Constans, ruler of the Western Roman Empire, had become increasingly unpopular among the legions.
• His arbitrary rule and favoritism alienated both the army and the Roman elite.
• By 350 CE, discontent in the ranks of the military had reached a breaking point.

2. The Army Proclaims Magnentius Emperor (January 18, 350 CE)

• On January 18, 350 CE, in Autun (modern France), the army elevated Magnentius to the rank of Augustus, openly declaring rebellion against Constans.
• Magnentius, a capable general and popular leader, quickly gained support from the military and key western provinces.

3. The Fall of Constans and the Beginning of Civil War

• Upon learning of Magnentius’ usurpation, Constans fled southward toward Spain, seeking refuge.
• He was caught and executed by Magnentius' forces in early 350 CE, leaving Magnentius in control of the Western Roman Empire.
• This triggered a civil war with Constantius II, who, as the last surviving son of Constantine the Great, vowed to avenge his brother’s death.

4. The Struggle for the Empire

• The civil war between Magnentius and Constantius II lasted from 350 to 353 CE, culminating in:
  • The Battle of Mursa (351 CE)—one of the bloodiest battles in Roman history, where Magnentius was defeated.
  • The final Roman campaign in Gaul (353 CE), where Magnentius, losing support, fled into exile and committed suicide.

5. Conclusion: A Failed Bid for Power

• Though Magnentius successfully overthrew Constans, he was ultimately unable to defeat Constantius II, leading to his downfall in 353 CE.
• His pagan beliefs and anti-Christian stance may have also contributed to his loss of elite and imperial support.
• The civil war significantly weakened the Western Roman military, paving the way for future instability and external invasions.

Magnentius' brief rule and ultimate defeat exemplified the power struggles and fragmentation that plagued the Roman Empire in the 4th century, foreshadowing further internal conflicts and the eventual fall of the Western Roman Empire.

Constans, abandoned by all except a handful of retainers, is slain shortly afterwards by a troop of light cavalry near the Pyrenees.

Magnentius quickly attracts the loyalty of the provinces in Britannia, Gaul, and Hispania, in part because he proves to be far more tolerant towards both Christians and Pagans.

He applies his control on Italia and Africa through the election of his men to the most important offices.

Nepotianus is the son of Eutropia, half-sister of Emperor Constantine I, and of Virius Nepotianus; on his mother's part, he is grandson of Emperor Constantius Chlorus and Flavia Maximiana Theodora.

He proclaims himself emperor and enters Rome with a band of gladiators on June 3, 350, which causes the Praefectus urbi Titianus (or Anicius, or Anicetus), allied to Magnentius, to flee, after being defeated at the head of an undisciplined force of Roman citizens.

Magnentius quickly deals with the situation by sending his trusted magister officiorum Marcellinus to Rome.

Nepotianus is killed in the resulting struggle (June 30, 350), his head put on a lance and brought around the city (Eutropius).

In the following days, Eutropia too is killed, within the persecution of the supporters of Nepotianus, most of whom are senators.

Magnentius fails, however, to win failing to win recognition from Constantius.

The outstanding marble sarcophagus of Christian politician Junius Bassus, vir clarissimus and vicarius of Rome as well as praefectus urbi from March 25 to 25 August 25, 359, is, with its double frieze of figures grouped in small architectural niches, an early example of the high relief sculpture favored by early Christians.

The youthful, beardless Christ in the upper central niche draws from images of the pagan deity Apollo, an example of the adaptation of figures from pagan mythology as Christian images and symbols.

Constantius, after dealing with the rebellions of Magnentius and Sylvanus, feels the need for a permanent representative in Gaul.

His twenty-three year-old nephew Julian is in 355 summoned from Greece to appear before the emperor in Mediolanum.

This is a difficult decision for a paranoid ruler who regards all his relatives with intense suspicion and has already put to death two uncles and seven cousins, including Julian's half-brother Constantius Gallus, but Constantius' own family purges had left him little choice: Julian is his sole surviving adult male close relative.

Julian, who has studied at Pergamon, at Ephesus, and lately at Athens, has adopted the cult of Sol Invictus, the Unconquered Sun.

He had arrived at Sirmium “still wearing his student's gown.”

Julian is on November 6 duly proclaimed and invested as Caesar of the West, an honor that he accepts with justifiable foreboding, and marries Constantius' sister, Helena. (She will die after five years of marriage-the fate of their issue, if any, is unknown.)

After his experience with Gallus, Constantius intends his representative to be more a figurehead than an active participant in events, so he at once packs Julian off to Gaul with a small retinue; Constantius' prefects in Gaul will keep him in check.

Julian, at first reluctant to trade his scholarly life for war and politics, will eventually take every opportunity to involve himself in the affairs of Gaul.

Constantius, who is primarily interested in religious affairs, publishes a decree in 356 ordering the closure of all pagan temples throughout the Empire and bans the veneration of non-Christian images.

His interventions have created a “caesaro-papism” that is unfavorable to the church, for after the Battle of Mursa the emperor had become violently Arian.

The Christological problem has moved to the forefront.

As sole ruler after 353, Constantius tries to create religious unity in the empire under Arian Christianity.

Under his leadership, the Nicene party (orthodox Christians) is largely crushed.

The extreme Arians now declare that the Son was “unlike” (anomoios) the Father.

Constantius twice (339, 356) exiles Athanasius, the influential orthodox bishop of Alexandria, but the religious unity he seeks is destined to be short-lived.

The Arian controversy, the continuation of which has been aided by the conflicting politics of the empire after the death of Constantine, has emerged as three distinct types by the mid-fourth century.

Radical Arianism holds that the Son was "dissimilar" to the Father; homoeanism maintains that the Son was similar to the Father; and semi-Arianism veers off into orthodoxy in its position that the Son was similar yet distinct from the Father.

Constantius passes laws against paganism, and pagans as well as orthodox Nicaeans (Homoiousians) and extremist Arians (Anomoeans) are persecuted, for in 356-357 several edicts proscribe magic, divination, and sacrifices and order that the temples be closed.

The homoean party scores an initial success in 357, after which the semi-Arians join the orthodox ranks.

From 353 to 356 Bishop Hosius, who had been ecclesiastical advisor to Constantius’s father, the emperor Constantine, has strongly resisted the efforts of Constantius to have Athanasius condemned by the Western bishops and in a famous letter reproves the Arian emperor for intruding into ecclesiastical matters.

Summoned to Sirmium in 356 and detained at court for a year, after threats and physical violence, Hosius signs the Arian formula of Sirmium in 357.

Hosius retracts his signature, however, before he dies in Córdoba late in the year.

Constantius has ordered the closure of all pagan temples throughout the Empire and banned the veneration of non-Christian images, but when the emperor visits Rome for the first time to celebrate his victory over Magnentius and to address the Senate and the people in 357, he is so struck by its pagan grandeur—the historian Ammianus Marcellinus portrays him as deeply moved—that he apparently suspends the application of these measures.