The Pontic Campaign is a war between the Second Roman Republic, the Sassanid Empire and their Antic, Slavic, Gothic, Lasikan, Iberian and Bosporan allies on one side, and mostly nomadic peoples (Huns, Alani, Onogurs and a few Slavic tribes) on the other side.
It took place in 372-374 and ended with the annihilation of Black Huns, "free" Sarmatians, Western Alani, Onogurs and Sabirs as peoples, the death of hundreds of thousands of nomads and the enslavement of even more, the establishment of the Kingdom of the Antes and Roman control over much of the Pontic Steppe.
Huns and Alani had migrated into the Pontic space in the 350s and overthrown the Gothic Empire. Warriors under Hunnic leadership as well as refugees spilled into Roman Dacia and threatened the Danube border throughout the 360s. After initial defeats, the Roman Republic was able to defend the Danube limes, and border civitates let in limited amounts of refugees in an organised manner. North of the Danube, though, the attacks and migratory movements effaced the old order in Magna Germania and destroyed existing proto-state and tribal structures there, creating further potentially dangerous instability at the gates of the Roman Republic.
Under the impression of these dangers, the Roman Maximum Collegium Militum, the Conventum and the Consuls abandoned the predominantly defensive military doctrine of the early Second Republic. A punitive campaign against the Huns and their allies was conducted on the Pannonian plains in 367. Diplomatic and military preparations were undertaken for a great joint war effort which would defuse the powder keg of the "wild field" once and for all - or so it was hoped.
When another Hunnic attack hit the Roman civitas of Prioboridava at the North-Eastern border of the Republic, East of the Carpathian mountains, in April 372, the Consuls Alexandros and Pamphylikos, together with the Sassanid Shahanshah Shapur II., the Antic King Bozh and a number of smaller tribes began their offensives.
On board of large Roman vessels, large, well-equipped and well-trained Roman cavalries as well as infantry units and tross were transported upriver on the Tyras (OTL Dniester), Hypanis (OTL Southern Bug) and Borysthenes (OTL Dnieper). Roman ships also brought equally strong Sassanid divisions upriver on the Tanais (OTL Don). A number of castra were built along the river. They encountered no significant resistance.
Acting on intelligence that the main body of the Hunnic forces were dwelling between the Hypanis and the Borysthenes (in central Ukraine OTL), the Roman MCM prepared a multi-pronged encirclement campaign. In the North, Bozh`s forces were instructed to prevent any Huns from escaping toward the North and into the woods. By the end of summer, no major battle had been fought yet, and Rome had built up a huge amount of troops and established safe and reliable supply chains. In the West, small units constituted by the guards of Dacian and Moesian civitates and their Costoboci and Roxolani allies secured the land up to the Pyretus (OTL Prut). In the East, Sassanid forces became engaged with several smaller bands of nomadic warriors, who were easily defeated and killed or enslaved. Provisional camps were built along the Ra (OTL Volga). The negotiated role of the Sassanids would be to prevent armed nomads from crossing the Tanais and the Ra. Their actual role would be more comprehensive and sombre, as 373 would begin to show.
Throughout the harsh winter of 372/3, the allied forces limited themselves to combing wide perimeters of their castra. While Romans, Sassanids and their allies enjoyed ample food supplies, which arrived by ship from the South, the nomads, who were now effectively prevented from plundering agricultural settlements, were probably coerced to slaughter much of their livestock to survive the long winter.
In the spring of 373, Romans and Antes launched their minutiously planned direct attack on the dwellings of the Huns. Bozh`s warriors approached them from the North, while Roman divisions marched on them from their castra on the Hypanis in the West and on the Borysthenes in the East. It took less than two weeks before major battles occurred on all three fronts. After severe defeats, the "Huns" (among which there were many Alani, Slavs and smaller Ugro-Finnic and Caucasian tribes) attempted to retreat into improvised fortifications. The biggest one among them was located near OTL Bobrynets. None of them was able to withstand Roman and Sassanid anti-siege weaponry - and in the heat of the summer of 373, hundreds of thousands of people were on the run in the pontic steppe.
Roman, Antic and Sassanid tacticians were, for the most time, able to control and contain this flight and direct it Eastward, where the Huns would hit the Borysthenes in a region full of dangerous rapids. Roman forces were planned to contain them from the South and pursue them fron the West, while Antic forces would contain them from the North, leaving the nomads with only three choices: dying in combat, drowning in the Borysthenes, or submitting into captivity.
The failure of this maneuver was the only major defeat of Rome and its allies in the Pontic Campaign. While Roman forces held the Western and Southern fronts successfully, the Hunnic riders, when pushed toward the steep valley of the Borysthenes, headed Northward and managed to break though Antic lines. (Bozh`s forces were sometimes weakend by a lack of understanding between Roman military-technical advisors and Antic warriors, who had not been sufficiently trained on the new weapons brought by the Romans.)
The rapids prevented the Classis Romana from sending quick reinforcements Northward in pursuit of the Huns, so the Romans and Antes present in the battlefield had to push on. A great number of Huns managed to cross the Borysthenes on a Roman military bridge, which local forces were unable to defend, while a smaller number of refugees possibly rode further Northward and into the woodlands, where they most likely survived the Pontic Campaign and became absorbed by various Slavic tribes.
While the Huns fled North- and Eastwward, local militias of Roman civitates and their allies had divided the land between Dacia`s Carpathian border and the river Pyretus among themselves, demarking formally the claims of the new civitates of Vadum Hierasi (OTL Pascani), Vallis Nigra / Berehomet, Siniacum (OTL Storozhynets), Hierasium (OTL Iasi), Basiloion (OTL Vaslui) and Berlidava (OTL Bârlad), whilst pushing some former inhabitants Eastward, absorbing many of them into the forces which, from April to June, conquered the land between the Pyretus and the Tyras. In more than a dozen middle-sized battles, tens of thousands of Huns and anti-Roman Slavs and Sarmatians (who were also considered "Huns" by the conquerors) died in this militarily peripheral theatre of the Pontic Campaign, which nevertheless left deep traces. Federal Roman forces lend their support to this conquest from their two main castra on the Tyras.
The final defeat and annihilation of the Huns and all those who were caught with them came in 374, when Sassanid, Lasikan and Iberian forces rode Westward from the castra on the Tanais and, together with Roman, Taurean Gothic and a few Antic forces, encircled the main body of the nomadic populace which had migrated into Europe on the steppe between the Borysthenes and the Tanais, and killed tens of thousands of them before the nomads capitulated and offered the heads of their leaders. A huge number of slaves were then marched into internment camps near the castra at the shore of the Asowian Sea and the Tanais River, from where they were sold into Sassanid slavery. Their exact number is lost to history, but Sassanid shahs paid the Roman MCM an enormous amount of gold for the Roman contribution in obtaining 74,000 slaves handed over by Romans to the Sassanids.
Fightings did not stop entirely after the cruel finale in June 374 - conquests in the West and slave hunts in the East continued for the rest of the year. Early in 374, two civitates of predominantly provincial Roman population (with many Dacian and Slavic elements) formed in the immediate vicinity of the two castra on the Tyras: Tyraspolis (OTL Tiraspol) and Tigina (OTL Bender). They sought adherence to the Republic, and negotiations were begun. The new power relations crystallised in the erection of new societates liberorum and similar rural structures in the fertile hinterland between the upper Pyretus and the upper Tyras, while the defeated former inhabitants of these lands had fled to the marshes on the lower reaches of both rivers. Those who had not yet been lucky in the distribution of the conquest`s spoils moved further East and engaged into another war of conquest, in which, tolerated or even encouraged by the Republic, mixed militia of Romans and non-Romans formed an alliance with the Slavic tribal confederation of the Dulabi against other Slavic tribes and clans and conquered their lands between the Tyras and the Hypanis, relying heavily on the military infrastructure left behind by the Roman federal troops.
In the East, the returning Sassanid army did not limit itself to marching the captives into slavery - they attacked and defeated another tens of thousands of nomads living North of the Ebrus ridge and enslaved them, too.
The new political and military reality in the pontic space created by the Pontic Campaign was formalised at a conference in Chersonesos on Tauris in 375:
- The civitates West of the Pyretus would join the Roman Republic.
- The land between the Pyretus and the Tyras would become a margo: Rei Publicae Romanae Margo Tyrensis. Land would be divided between the two Roman civitates, a Dacian tribe and the Slavic tribe of the Tivertsi
- The land between the Tyras and the Hypanis would become a margo, too: Rei Publicae Romanae Margo Hypanensis. At the periphery of the political talks, many contracts were signed between the new lords of this margo and Roman collegia, especially from the domain of civil engineering: the land between Tyras and Hypanis would need a lot of canals, aquaeducts and roads to become productive...
- The Taurean margo would be extended for more than a hundred miles upriver along the Borysthenes and the Tanais. Permanent Roman naval bases would be established at Kerknitis (on Tauris), Phanagoria (on the margo`s Sindican land strip), Kallipolis and Castra Luhana (on the Tanais) as well as Nikopolis, Chortitia (OTL Zaporizhyn), Neapolis Borysthenea and Severopolis (OTL Dnepropetrowsk) on the Borysthenes. Aorsean Sarmatians and Severian Slavs were incorporated into the Greek-speaking margo.
- The Antes establish an independent kingdom between the Tanais and the Ra.
- Roman, Antic and Sassanid forces would continue to co-operate against invasions from the steppe, alerting each other immediately. Rome would be responsible for the steppe West of the Tanais, while the Sassanids would be responsible for the steppe East of the Ra, with the land between the Tanais and the Ra being under the responsibility of the Antes..