Constantine is one of the most important Roman Emperor that largely reformed and where favored the spread of Christianity. Among his most significant, the reorganization of the administration and the army, the creation of a new capital in the east (Constantinople, now Istanbul) and the promulgation of the Edict of Milan on religious freedom.
To reconstruct the life of Constantine the Great, we refer to the sources, the first of Eusebius of Caesarea, who wrote about his actions and the period of his Empire. Eusebio fact wrote the "Ecclesiastical History" in which he speaks to the figure of this great emperor who brought great benefits to the Christian religion, as well as a hagiographic text dedicated exclusively to the life of Constantine, with the title "Life of Constantine." In addition to these texts can also refer to the work of Lattanzio "De mortibus persecutorum" in which we refer often to Constantine and the Edict of Tolerance.
- Constantine, son of Costanzo, Emperor Tetrarch between 305 and 306 and Elena, and little is known of his childhood. We know that when in 288 Constantius was appointed Prefect of the Praetorian and began his political career, Constantine was entrusted to Diocletian, the Augustus of the East, and is well educated in the city of Nicomedia. Already in this period of his life Constantine began his military career and was appointed tribune ordinis first, and with this office participated in the war against the Sarmatians. When in 305 Diocletian and Maximian abdicated in favor of their Caesars, Galerius and Constantius, Constantine joined his father in Britain and fought with his army. So the following year, when his father died, it was the same army proclaimed Constantine as the successor of Constantius, then appointing the new Augustus for the western part of the Empire; this will put into question the. Egg tetrarchico system, which had been specially wanted to limit the power of the army in the appointment of the emperors.
- In 306 Constantine then had been appointed Emperor following the principle established by the dynastic succession, that did not keep account of the desire for change proposed by Diocletian and therefore resulted in a series of civil wars. At the political level the empire was ruled by Galerius Maximinus, Licinius and Constantine, with Maxentius remained as usurper of the ruling regime in Rome, so that following the death of Galerius, which occurred in 311, there was a coalition against Maxentius. Constantine with his army defeated Maxentius for two consecutive times, first in Turin and then in Verona, until the final defeat will happen with the Battle of the Milvian Bridge, fought in 312 at Saxa Rubra.
- It is also at this time that would take place the conversion to Christianity of Emperor Constantine, following the vision of the sign of the cross on the solar corona, and the fateful written premonitory "in hoc signo vinces" (in this sign you will conquer) that would have appeared in dream Constantin
- In 313 Constantine and Licinius met in Milan to take the agreements on freedom of worship within the boundaries of the Empire, thus ensuring even the Christians to profess their faith freely. This pact, improperly known as the Edict of Milan, was then rescript of Licinius at its entrance in Kocaeli, and in which it was established even the return of all the places of worship to their rightful owners, over which was given the opportunity to edificarne new, no more secrets and hidden. Licinio bride then Constantine's sister, Constance, that will not prevent the occurrence of disagreements between the two, which will lead to the final defeat of Licinius in 324, and his final killing.
- Since then 324 will be the only emperor Constantine, and from 326 will begin construction of a new capital for his empire, which will be planted on the old city of Byzantium, the city will be provided with a seat for the Senate and which will be called Constantinople. The site chosen had a strategic importance, since it was located near the borders of the Danube and the eastern ones who were constantly threatened by invaders. In 330 the new city was ready, and was inaugurated with great fanfare, occupying a space of four times that of the ancient city, with walls of 15 stages moved further to the west than the line of the above. It is precisely here that Constantine is baptized will, in what will then remain the capital of the Byzantine Empire until 1453, the year of the capture of the city by the Turks, led by Emperor Mehmet Fathi, who put fire to the city to three days and three nights.
- Constantine the Great called the First Council of Nicaea in 325, at which the Nicene Creed was professed by Christians.
- Constantine's death occurred in Kocaeli, on May 22, 337, when he was still busy preparing yet another military campaign, this time against the Sassanids. For the succession Constantine appointed a sole heir, but he decided to share power among his three sons, Constans, Constantine II and Constantius II.