Empire of Pannonia (Seven Roman States)

The Pannonian Empire (or Pannonia) was the predominantly Greek-speaking Eastern European part of the Roman Empire throughout Late Antiquity and the Middle Ages. Also known as the Romano-Greek Empire, or simply the Roman Empire by its inhabitants and neighbours. It was centered on the capital of Sirmium, located in Illyria.

Roman Background and Foundation of the Tetrarchy
The army of the Roman Empire succeeded in conquering a vast collection of territories covering the entire Mediterranean region and much of Western Europe. These territories consisted of many different cultural groups, ranging from primitive to highly sophisticated. Generally speaking, the eastern Mediterranean provinces were more urbanized and socially developed, having previously been united under the Macedonian Empire and Hellenized by the influence of Greek culture. In contrast, the western regions had mostly remained independent from any single cultural or political authority, and were still largely rural and less developed. This distinction between the established Hellenized East and the younger Latinized West persisted and became increasingly important in later centuries.

Under the reign of the Emperor Diocletian, the political division of the Roman Empire began. In 285, he promoted Maximian to the rank of Augustus (Emperor) and gave him control of the Western regions of the Empire. In 293, Galerius and Constantius Chlorus were appointed as their subordinates (Caesars), creating the First Tetrarchy. This system effectively divided the empire into four major regions and created separate capitals besides Rome as a way to avoid the civil unrest that had marked the 3rd century. In the West, the capitals were Maximian's Mediolanum (now Milan) and Constantius' Trier. In the East, the capitals were Sirmium and Nicomedia. On 1 May 305, the two senior Augusti stepped down, and their respective Caesars were promoted to Augusti and appointed two new Caesars, thus creating the Second Tetrarchy.

These men were from the Roman province of Illyria, several in the city of Sirmium, which would become one of the four capitals under this system. From the time of Domitian (81–96), when over half the Roman army was deployed in the Danubian regions, the Illyrian provinces had been the most important recruiting ground of the auxilia and later the legions. In the 3rd century, Romanised Illyrians came to dominate the army's senior officer echelons. Ultimately, the Illyrian officer class seized control of the state itself.

The four Tetrarchs based themselves not at Rome but in other cities closer to the frontiers, mainly intended as headquarters for the defence of the empire against bordering rivals (notably Sassanian Persia) and barbarians (mainly Germanic, and an endless procession from the eastern steppe; many nomadic or elsewhere chased tribes) at the Rhine and Danube.

Rise of Pannonia under Licinius
Born to a Thracian family in Moesia Superior, Licinius accompanied his close childhood friend, the future emperor Galerius, on the Persian expedition in 298. He was trusted enough by Galerius that in 307 he was sent as an envoy to Maxentius in Italy to attempt to reach some agreement about his illegitimate status. Galerius then trusted the eastern provinces to him when he went to deal with Maxentius personally after the death of Flavius Valerius Severus. Upon his return to the east, Galerius elevated Licinius to the rank of Augustus in the West on November 11, 308. He received as his immediate command the provinces of Illyricum, Thrace and Pannonia.

In 310 he took command of the war against the Sarmatians, inflicting a severe defeat on them and emerging victorious. Then on the death of Galerius, in May 311, Licinius entered into an agreement with Maximinus Daia, to share the eastern provinces between them. By this point, not only was Licinius the official Augustus of the west, but he also possessed part of the eastern provinces as well, as the Hellespont and the Bosporus became the dividing line, with Licinius taking the European provinces and Daia taking the Asian. This final division of the Eastern Roman Empire is considered by many to be the formation of Pannonia as an independent nation from its other Roman neighbors.

An alliance between Daia and Maxentius forced the two remaining emperors to enter into a formal agreement with each other. So in March 313 Licinius married Flavia Julia Constantia, half-sister of Constantine, at Mediolanum (now Milan); they had a son, Licinius the Younger, in 315. Their marriage was the occasion for the jointly-issued "Edict of Milan" that restored confiscated properties to Christian congregations and allowed Christianity to be professed in the empire.

Daia, in the meantime decided to attack Licinius. Leaving Syria with 70,000 men, he reached Bythinia, although harsh weather he encountered along the way had gravely weakened his army. In April 313, he crossed the Bosporus in Thrace and went to Byzantium, which was held by Licinius' troops. Undeterred, he took the town after an eleven-day siege. He moved to Heraclea, which he captured after a short siege, before moving his forces to the first posting station. With a much smaller body of men, possibly around 30,000, Licinius arrived at Adrianople while Daia was still besieging Heraclea. On 30 April 313, the two armies clashed at the Battle of Tzirallum, and in the ensuing battle Daia's forces were crushed. Ridding himself of the imperial purple and dressing like a slave, Daia fled to Nicomedia, but Licinius chose not to pursue.

In 314, a civil war erupted between Licinius and Constantine, in which Constantine used the pretext that Licinius was harbouring another of Constantine’s brothers-in-law, Bassianus, whom Constantine accused of plotting to overthrow him. Constantine, however, was defeated at the Battle of Cibalae in Pannonia (October 8, 314).

Over the next ten years, the two imperial colleagues maintained an uneasy truce. Licinius kept himself busy with a campaign against the Sarmatians in 318, but temperatures rose again in 321 when Constantine pursued some Sarmatians, who had been ravaging some territory in his realm, across the Danube into what was technically Licinius’s territory. When he repeated this with another invasion, this time by the Goths who were pillaging Thrace, Licinius complained that Constantine had broken the treaty between them. Constantine wasted no time going on the offensive. But he again suffered defeat when Licinius's fleet of 350 ships crushed Constantine's fleet in 323. Then in 324, Constantine, tempted by the "advanced age and unpopular vices" of his colleague, again declared war against him. But yet again Licinius's military superiority rang through when Constantine's army, despite some minor successes, was utterly destroyed at the Battle of Adrianople in 324. This destroyed all of Constantine's plans for a united Roman Empire, and he returned the next year to Rome a defeated man.

In 333, Licinius died, often regarded as Savior of Pannonia and a Saint of the Illyrian Church and its respective sects. Despite Constantine's every effort to blacken the reputation of his imperial colleague, his active attempts to portray his brother-in-law as a pagan supporter failed to move many of the Roman people, especially in the East. In fact, Licinius was a committed supporter of Christians. He co-authored the Edict of Milan which ended the Great Persecution, and re-affirmed the rights of Christians in his portion of the empire. He also added the Christian symbol to his armies, and attempted to regulate the affairs of the Church hierarchy just as Constantine and his successors were to do. His son, Licinius II, would later implement important changes into Pannonia's civil and religious constitution.