Constantine I, also known as Constantine the Great, was a Roman emperor from AD 306 to 337 and the first Roman emperor to convert to Christianity. He played a pivotal role in elevating the status of Christianity in Rome, decriminalizing Christian practice and ceasing Christian persecution in a period referred to as the Constantinian shift. This initiated the Christianization of the Roman Empire. Constantine is associated with the religiopolitical ideology known as Caesaropapism, which epitomizes the unity of church and state. He founded the city of Constantinople and made it the capital of the Empire, which remained so for over a millennium.
Diocletian, nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia. Diocles rose through the ranks of the military early in his career, eventually becoming a cavalry commander for the army of Emperor Carus. After the deaths of Carus and his son Numerian on a campaign in Persia, Diocles was proclaimed emperor by the troops, taking the name Diocletianus. The title was also claimed by Carus's surviving son, Carinus, but Diocletian defeated him in the Battle of the Margus.
The Tetrarchy was the system instituted by Roman emperor Diocletian in 293 AD to govern the ancient Roman Empire by dividing it between two emperors, the augusti, and their junior colleagues and designated successors, the caesares.
The 300s decade ran from January 1, 300, to December 31, 309.
The 310s decade ran from January 1, 310, to December 31, 319.
Year 313 (CCCXIII) was a common year starting on Thursday of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantinus and Licinianus. The denomination 313 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. This year is notable for ending of the persecution of Christians in the Roman Empire.
The 290s decade ran from January 1, 290, to December 31, 299.
The 280's decade ran from January 1, 280, to December 31, 289.
Year 306 (CCCVI) was a common year starting on Tuesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantius and Valerius. The denomination 306 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 307 (CCCVII) was a common year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Severus and Maximinus. The denomination 307 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 310 (CCCX) was a common year starting on Sunday of the Julian calendar. At the time, it was known as the Year of the Consulship of Andronicus and Probus. The denomination 310 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 311 (CCCXI) was a common year starting on Monday of the Julian calendar. At the time, it was known as the Year of the Consulship of Valerius and Maximinus. The denomination 311 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Galerius Valerius Maximianus was Roman emperor from 305 to 311. While acting as Caesar under Emperor Diocletian, Galerius obtained victory warring against the Sassanian Empire, defeating Narseh at the battle of Satala in 298 and possibly sacking the Sassanian capital of Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued the Edict of Toleration in Serdica (Sofia) in 311.
Maximian, nicknamed Herculius, was Roman emperor from 286 to 305. He was Caesar from 285 to 286, then Augustus from 286 to 305. He shared the latter title with his co-emperor and superior, Diocletian, whose political brain complemented Maximian's military brawn. Maximian established his residence at Trier but spent most of his time on campaign. In late 285, he suppressed rebels in Gaul known as the Bagaudae. From 285 to 288, he fought against Germanic tribes along the Rhine frontier. Together with Diocletian, he launched a scorched earth campaign deep into Alamannic territory in 288, refortifying the frontier.
Marcus Aurelius Valerius Maxentius was a Roman emperor from 306 until his death in 312. Despite ruling in Italy and North Africa, and having the recognition of the Senate in Rome, he was not recognized as a legitimate emperor by his fellow emperors.
Flavius Valerius Severus, also called Severus II, was a Roman emperor from 306 to 307, and a member of the Tetrarchy. He shared control of the western half of the empire with Constantine I, but spent most of his short reign in a civil war against the usurper Maxentius, who later killed him and took over Italy.
Pannonia Superior was a Roman province created from the division of Pannonia in 103 AD, its capital in Carnuntum. It overlapped in territory with modern-day Hungary, Croatia, Austria, Slovakia, and Slovenia.
The civil wars of the Tetrarchy were a series of conflicts between the co-emperors of the Roman Empire, starting from 306 AD with the usurpation of Maxentius and the defeat of Severus to the defeat of Licinius at the hands of Constantine I in 324 AD.
The Conference of Carnuntum was a gathering of ancient Roman rulers on 11 November 308, intended to stabilize the power-sharing arrangement known as the Tetrarchy. It was convened by the Eastern augustus (emperor) Galerius in the city of Carnuntum, which at the time was located in the Roman province of Pannonia Prima. A dispute over the title of augustus in the West had been ongoing since the previous year, when consecutive invasions by Severus II and Galerius had failed to recover Italy from the usurpers Maxentius and Maximian. Present at the conference were the retired Diocletian, and his former colleague, Maximian.
The siege of Segusio or siege of Susa was the first clash of the civil war between the Roman emperors Constantine the Great and Maxentius in the spring of 312. In that year, Maxentius had declared war on Constantine, claiming to intend to avenge the death of his father Maximian, who had committed suicide after being defeated by him. Constantine would respond with an invasion of northern Italy.
