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 cessation of the established ancient Roman religion. Constantine is also the originator of the religiopolitical ideology known as Constantinianism, which epitomizes the unity of church and state, as opposed to separation of church and state. He founded the city of Constantinople and made it the capital of the Empire, which remained so for over a millenium.
The labarum was a vexillum that displayed the "Chi-Rho" symbol ☧, a christogram formed from the first two Greek letters of the word "Christ" – Chi (χ) and Rho (ρ). It was first used by the Roman emperor Constantine the Great.
The 320s decade ran from January 1, 320, to December 31, 329.
Year 324 (CCCXXIV) was a leap year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Crispus and Constantinus. The denomination 324 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.
The Battle of the Milvian Bridge took place between the Roman Emperors Constantine I and Maxentius on 28 October 312 AD. It takes its name from the Milvian Bridge, an important route over the Tiber. Constantine won the battle and started on the path that led him to end the Tetrarchy and become the sole ruler of the Roman Empire. Maxentius drowned in the Tiber during the battle; his body was later taken from the river and decapitated, and his head was paraded through the streets of Rome on the day following the battle before being taken to Africa.
Valerius Licinianus Licinius was Roman emperor from 308 to 324. For most of his reign, he was the colleague and rival of Constantine I, with whom he co-authored the Edict of Milan that granted official toleration to Christians in the Roman Empire. He was finally defeated at the Battle of Chrysopolis, and was later executed on the orders of Constantine I.
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 Julius Crispus was the eldest son of the Roman emperor Constantine I, as well as his junior colleague (caesar) from March 317 until his execution by his father in 326. The grandson of the augustus Constantius I, Crispus was the elder half-brother of the future augustus Constantine II and became co-caesar with him and with his cousin Licinius II at Serdica, part of the settlement ending the Cibalensean War between Constantine and his father's rival Licinius I. Crispus ruled from Augusta Treverorum (Trier) in Roman Gaul between 318 and 323 and defeated the navy of Licinius I at the Battle of the Hellespont in 324, which with the land Battle of Chrysopolis won by Constantine forced the resignation of Licinius and his son, leaving Constantine the sole augustus and the Constantinian dynasty in control of the entire empire. It is unclear what the legal status of the relationship Crispus's mother Minervina had with Constantine was; Crispus may have been an illegitimate son.
The Battle of Chrysopolis was fought on 18 September 324 at Chrysopolis, near Chalcedon, between the two Roman emperors Constantine I and Licinius. The battle was the final encounter between the two emperors. After his navy's defeat in the Battle of the Hellespont, Licinius withdrew his forces from the city of Byzantium across the Bosphorus to Chalcedon in Bithynia. Constantine followed, and won the subsequent battle. This left Constantine as the sole emperor, ending the period of the Tetrarchy.
The Battle of Adrianople was fought in Thrace on July 3, 324, during a Roman civil war, the second to be waged between the two emperors Constantine I and Licinius. Licinius was soundly defeated, his army suffering heavy casualties as a result. Constantine built up military momentum, winning further battles on land and sea, eventually leading to the final defeat of Licinius at Chrysopolis.
The Battle of Tzirallum was part of the civil wars of the Tetrarchy fought on 30 April 313 between the Roman armies of emperors Licinius and Maximinus. The battle location was on the "Campus Serenus" at Tzirallum, identified as the modern-day town of Çorlu, in Tekirdağ Province, in the Turkish region of Eastern Thrace. Sources put the battle between 18 and 36 Roman miles from Heraclea Perinthus, the modern-day town of Marmara Ereğlisi.
The Battle of Cibalae was fought in 316 between the two Roman emperors Constantine I and Licinius. The site of the battle, near the town of Cibalae in the Roman province of Pannonia Secunda, was approximately 350 kilometers within the territory of Licinius. Constantine won a resounding victory, despite being outnumbered.
The Battle of Mardia, also known as Battle of Campus Mardiensis or Battle of Campus Ardiensis, was probably fought at modern Harmanli (Bulgaria) in Thrace, in late 316/early 317 between the forces of Roman Emperors Constantine I and Licinius.
Martinian was Roman emperor from July to September 324. He was raised to the purple by the emperor Licinius, whom he had hitherto served as a senior bureaucrat, during Licinius's civil war against the emperor Constantine I. Constantine defeated both emperors and forced them to abdicate, and executed them after initially showing leniency.
Aurelius Valerius Valens, rarely enumerated as Valens I, was briefly Roman emperor from late 316 to early 317. He was proclaimed emperor by Licinius, emperor of the East, during his war against Constantine I, emperor of the West.
Licinius II, also called Licinius Junior or Licinius Caesar, was the son of the Roman emperor Licinius I. He held the imperial rank of caesar between March 317 and September 324, while his father was augustus, and he was twice Roman consul. After losing a civil war, his father lost power and both he and Licinius Junior were eventually put to death.
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 Battle of Byzantium (Byzantion) took place during the wars of the successors of Alexander the Great between the generals Antigonus Monopthalmus and Cleitus the White. It was a two-day-battle fought near Byzantium at the Hellespont in 317 BC and resulted in a stunning Antigonid victory.
The siege of Byzantium was carried out some time between July and September 324 by the forces of the Roman emperor Constantine I during his Second Civil War against his rival, co-emperor Licinius. It would have been started simultaneously with the naval battle of the Hellespont in which Constantine's son and caesar Crispus defeated the Lycinian navy commanded by Admiral Abanto.
The Battle of Brescia was a confrontation that took place during the summer of 312, between the Roman emperors Constantine the Great and Maxentius in the town of Brescia, in northern Italy. Maxentius declared war on Constantine on the grounds that he wanted to avenge the death of his father Maximian, who had committed suicide after being defeated by him. Constantine would respond with a massive invasion of Italy.
