Early Christian churches in Milan are the first churches built immediately after the Edict of Milan (Edictum Mediolanense) in February 313, issued by Constantine the Great and Licinius, which granted tolerance and religious liberty to Christianity within the Roman Empire.
Historical and artistic context
Ever since the fall of the Severan dynasty, which ruled the Roman Empire between 193 and 235, rivals for the imperial throne had bid for support by either favouring or persecuting Christians. During the following period known as the crisis of the Third Century (AD 235–284) the Roman Empire nearly collapsed under the combined pressures of invasion, civil war, plague, and economic depression. The Crisis began with the assassination of Emperor Alexander Severus at the hands of his own troops, initiating a fifty-year period in which 20–25 claimants to the title of Emperor, mostly prominent Roman army generals, assumed imperial power over all or part of the Empire.
During the Civil wars of the Tetrarchy, starting in 306 AD with the usurpation of Maxentius and the defeat of Flavius Valerius Severus, and ending with the defeat of Licinius at the hands of Constantine I in 324 AD, Diocletian moved the capital of the Western Roman Empire from Rome to Mediolanum, the ancient Milan. Diocletian chose to reside at Nicomedia in the Eastern Empire, leaving his colleague Maximian at Mediolanum. Maximian built several gigantic monuments, the large circus (), the thermae or "Baths of Hercules", a large complex of imperial palaces, and other services and buildings of which fewer visible traces remain. Maximian increased the city area surrounded by a new, larger stone wall (about long) with many 24-sided towers.
An edict of toleration was issued by the emperor Galerius from Serdica and posted at Nicomedia on 30 April 311. By its provisions, the Christians, who had "followed such a caprice and had fallen into such a folly that they would not obey the institutes of antiquity", were granted an indulgence. Their confiscated property, however, was not restored until 313 when instructions were given for the Christians' meeting places and other properties were to be returned and compensation paid by the state to the current owners: The Christian community of Mediolanum is alleged to have contributed its share of martyrs during the Persecutions of the Church, but the first bishop of Mediolanum who has a firm historical presence is Mirocles, who was at the Council of Rome of 313.
It was from Mediolanum that the Emperor Constantine issued the Edict of Milan in 313 AD, granting tolerance to all religions within the Empire, thus paving the way for Christianity to become the dominant religion of the Empire. Constantine was in Mediolanum to celebrate the wedding of his sister to the Eastern Emperor, Licinius. The agreement between Constantine and Licinius directed the provincial magistrates to execute its orders at once and with all energy, so that public order may be restored and the continuance of the Divine favour may "preserve and prosper our successes together with the good of the state." It marked the beginning of profound and radical transformations; the encouragement of Christian worship led to the methodical destruction of Christian monuments invisible to the authorities.
Stones taken from the amphitheatre have been recognized in the foundations of the Basilica of San Lorenzo (; ), indicating the demolition of the large building () This use was justified because of the presence of waterways around the area where San Lorenzo was built, and because there was a scarce presence of large stones in Milan, being in a plain clay. Whether this fact, the positioning of the famous columns before the courtyard indicates that the building of the great cathedrals of the imperial era was also done at the expense of Roman buildings.
Constantinian churches
The early Christian basilicas in Mediolanum can be divided into several categories, corresponding to their periods.