The migration period brings Dacia linguistic and religious change.

The Dacians assimilate many Slavic words into their lexicon and, although modern Romanian is a Romance language, some linguists estimate that half of its words have Slavic roots.

Baptism of the Dacians had begun around 350, when Bishop Ulfilas preaches the Arian heresy north of the Danube.

Soon after saints Cyril and Methodius convert the Bulgars to Christianity in 864, Dacia's Christians adopt the Slavonic rite and became subject to the Bulgarian metropolitan at Ohrid.

The Slavonic rite will be maintained until the seventeenth century, when Romanian becomes the liturgical language.

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.

The First Bulgarian Empire, East Francia, and Moravia, which had fought each other for control of the Carpathian Basin, had occasionally hired Hungarian horsemen as soldiers.

The Hungarians who dwelt in the eastern regions of the Pontic steppes were therefore familiar with their future homeland when they started their their "land-taking".

The ethnic configuration of the northern Balkans is altered permanently by invasions of Magyars from the steppe, who settle the Plain of Hungary, named for these fierce tribes of mounted nomads, and gain full control of the Carpathian Basin, including Transylvania.

The Hungarian conquest starts in the context of a "late or 'small' migration of peoples".

Contemporary sources attest that the Hungarians crossed the Carpathian Mountains following a joint attack in 894 or 895 by the Pechenegs and Bulgarians against them.

They first take control over the lowlands east of the River Danube and attack and in 900 occupy Pannonia (the region to the west of the river).

Exploiting internal conflicts in Moravia sometime between 902 and 906, the Hungarians annihilate this state.

Simeon was born in 864 or 865, as the third son of Knyaz Boris I of Krum's dynasty.

As Boris was the ruler who had Christianized Bulgaria in 865, Simeon has been a Christian all his life.

Because his eldest brother Vladimir had always designated heir to the Bulgarian throne, Boris had intended Simeon to become a high-ranking cleric, possibly Bulgarian archbishop, and had sent him to the University of Constantinople to receive theological education when he was thirteen or fourteen.

He had taken the name Simeon as a novice in a monastery there.

During the decade (from about 878 to 888) he spent in the imperial capital, he had received an excellent education and studied the rhetoric of Demosthenes and Aristotle.

He had also learned fluent Greek, to the extent that he is referred to as "the half-Greek" in Byzantine chronicles.

He is speculated to have been tutored by Patriarch Photios I of Constantinople, but this is not supported by any source.

Around 888, Simeon had returned to Bulgaria and settled at the newly established royal monastery of Preslav, where, under the guidance of Naum of Preslav, he has engaged in active translation of important religious works from Greek to Old Church Slavonic (Old Bulgarian), aided by other students from Constantinople.

Meanwhile, Vladimir had succeeded Boris, who had retreated to a monastery, as ruler of Bulgaria.

Vladimir has attempted to reintroduce paganism in the empire and possibly signed an anti-Constantinople pact with Arnulf of Carinthia, forcing Boris to reenter political life.

With the aid of loyal boyars and the army, Boris drives his dissolute son from the throne and has him blinded, unfitting him for rule.

He then convenes a council that confirms Christianity as the religion of the state and moves the administrative capital from Pliska to the Slavic town of Preslav to better cement the recent conversion.

The assembly also proclaims Bulgarian as the only language of state and church.

It is not known why Boris did not place his second son, Gavril, on the throne, but instead preferred Simeon.

Boris now retires permanently to monastic life, making generous grants to the Bulgarian Church and patronizing Slav scholarship.

Clement, according to his hagiography by Theophylact of Ohrid, was born in the southwestern part of the Bulgarian Empire, in the region then known as Kutmichevitsa.

Clement had participated in the mission of Cyril and Methodius to Great Moravia and, after the death of Cyril, had accompanied Methodius on his journey from Rome to Pannonia and Great Moravia.

After the death of Methodius himself in 885, Clement had headed the struggle against the German clergy in Great Moravia along with Gorazd.

After spending some time in jail, he had been expelled from Great Moravia and in 885 or 886 had reached the borders of Bulgaria together with Naum of Preslav, Angelarius and possibly Gorazd (according to other sources, Gorazd was already dead by that time).

Thereafter, the four of them were sent to the Bulgarian capital of Pliska where they had been commissioned by Boris I of Bulgaria to instruct the future clergy of the state in the Slavonic language.

After the adoption of Christianity in 865, religious ceremonies in Bulgaria had been conducted in Greek by clergy sent from Constantinople.

Fearing the growing influence of the Empire and weakening of the Bulgarian state, Boris views the adoption of the Old Slavonic language as a way to preserve the political independence and stability of Bulgaria.

With a view thereto, Boris had made arrangements for the establishment of two literary academies where theology was to be taught in the Slavonic language.

The first of the schools had been founded in the capital, Pliska, and the second in the region of Kutmichevitsa.

While Naum of Preslav had stayed in Pliska working on the foundation of the Pliska Literary School, Clement had been commissioned by Boris I to organize the teaching of theology to future clergymen in Old Church Slavonic in Kutmichevitza.

For a period of seven years (between 886 and 893) has Clement taught some thirty-five hundred disciples in the Slavonic language and the Glagolitic alphabet.

He is in 893, ordained archbishop of Drembica (Velika), also in Kutmichevica, a region that corresponds roughly with the territory of modern southern Albania, with some parts in present southwestern Macedonia.

The long-lasting peace with the Empire established by Simeon's father is about to end.

A conflict arises when Emperor Leo VI the Wise, allegedly acting under pressure from his mistress Zoe Zaoutzaina and her father Stylianos Zaoutzes, moves the marketplace for Bulgarian goods from Constantinople to Thessaloniki, where the Bulgarian merchants are heavily taxed.

The Bulgarians seek the protection of Simeon, who in turn complains to Leo.

However, the emperor ignores his embassy.

Forced to take action, Simeon invades the Empire from the north in the autumn of 894, meeting with little opposition due to the concentration of most imperial forces in eastern Anatolia to counter Arab invasions.

Informed of the Bulgarian offensive, the surprised Leo sends an army consisting of guardsmen and other military units from the capital to halt Simeon, but his troops are routed somewhere in the theme of Macedonia.

The Bulgarians take most of the Khazar mercenary guardsmen prisoners and kill many archons, including the army's commander.

However, instead of continuing his advance to the capital, Simeon quickly withdraws his troops to face a Magyar invasion from the north.

Bulgarian historians will later call these events "the first trade war in medieval Europe.”

The Magyars, as mounted nomads in contact with and often in alliance with Turkic tribes, have moved westward under Árpád and Kukszan, with one group following the Lower Danube valley and two other groups crossing the Carpathian passes, one of which enters into Transylvania in 895.

Having elected as their chief Árpád, the leader of their most powerful tribe, the Magyars cross the Carpathians en masse, probably in 895, and easily subjugate the peoples of the sparsely inhabited central plain, their first place of settlement.

Thought of as returning Huns, the Magyars come to be known as Hungarians.

Constantinople, unable to effectively respond to the Bulgarian campaign due to the engagement of its forces against the Arabs, persuades the Magyars to attack Bulgaria, promising to transport them across the Danube using the imperial navy.

Leo VI may have also concluded an agreement with Arnulf to make sure that the Franks do not support Simeon against the Magyars.

In addition, the talented commander Nikephoros Phokas is called back from southern Italy to lead a separate army against Bulgaria in 895 with the mere intention to overawe the Bulgarians.

Simeon, unaware of the threat from the north, rushes to meet Phokas' forces, but the two armies do not engage in a fight.

Instead, Constantinople offers peace, informing him of both the imperial foot and maritime campaign, but intentionally does not notify him of the planned Magyar attack.

Simeon does not trust the envoy and, after sending him to prison, orders the imperial navy's route into the Danube closed off with ropes and chains, intending to hold it until he has dealt with Phokas.

Despite the problems they encounter because of the fencing, the imperial forces ultimately manage to ferry the Magyar forces led by Árpád's son Liüntika across the Danube, possibly near modern Galaţi, and assists them in pillaging the nearby Bulgarian lands.

Once notified of the surprise invasion, Simeon heads north to stop the Magyars, leaving some of his troops at the southern border to prevent a possible attack by Phokas.

Simeon's two encounters with the enemy in Northern Dobruja result in Magyar victories, forcing him to retreat to Drǎstǎr.

The Magyars, after pillaging much of Bulgaria and reaching Preslav, return to their lands, but not before Simeon has concluded an armistice with Constantinople towards the summer of 895.

A complete peace is delayed, as Leo VI requires the release of the imperial captives from the Trade War.

The Bulgarian tsar, using a Magyar invasion in the lands of the neighboring Slavs in 896 as a casus belli, heads against the Magyars together with his Pecheneg allies and his father Boris I, who leaves the monastery for this occasion.

Gathering an enormous army, Tsar Simeon marches to the north eastern borders of the country.

He orders three days of fasting, saying that the soldiers should repent for their sins and seek help in God.

When this is done, the battle of Southern Buh, near the banks of the eponymous river, in modern Ukraine, begins.

It is long and unusually fierce but in the end the Bulgarians are victorious, defeating the Magyars completely and making them leave Etelköz forever to settle in Pannonia.