On October 29, 312, Constantine the Great entered Rome after his victory at the Battle of the Milvian Bridge. He was met with widespread jubilation, and a grand celebration took place in the city. The body of the defeated Maxentius was pulled from the Tiber River and posthumously beheaded.
Constantine succeeded his father, Constantinus Chlorus, as co-emperor in 306. After defeating his longtime rival, Maxentius, he became the sole ruler of the Western Roman Empire. In 313, he issued the Edict of Milan with Licinius, the Eastern Emperor, which openly favored Christianity. Constantine defeated Licinius at the Battle of Chrysopolis in 324, uniting the Empire under his control.
During his reign, artistic and literary works reflected an imperial policy heavily influenced by the newly authorized religion, resulting in a gradual transformation of public art into a distinctly Christian form.
Constantine believed that his military victories were due to the Christian God, who revealed the sign of the Cross to him, superimposed on the sun, at the Milvian Bridge. In his final battle, he ordered the monogram of Christ to be painted on his soldiers’ shields, establishing the significance of the cross and the chi-rho in later Christian iconography. His victory was commemorated in 315 with the construction of a triumphal arch in the Roman Forum.
Constantine was a patron mainly of architecture, particularly of churches. His most important undertaking was the foundation of a new capital, Constantinople (now Istanbul), which was begun in 324 and dedicated in 330. Many of the traditional features of Rome were reproduced, including a central forum, a senate house, an imperial palace and a main street called the Mese.
The churches sponsored by Constantine outside Constantinople included both martyria and city cathedrals. Among the former was the basilica of Old St Peter’s, which was built to house the Apostle’s shrine and serve as a funeral hall. Two of the best-known cathedrals founded by the Emperor are the Basilica Constantiniana, now the Basilica of S Giovanni in Laterano, and the double cathedral of Trier, Germany. An innovation of the period was the frieze sarcophagus, which had a forerunner in the Etruscan burial tradition.
Piero della Francesca’s Constantine’s Dream, part of the fresco cycle of the Legend of the True Cross (c. 1452–66; Arezzo), embellishes the legend of Constantine’s vision at the Milvian Bridge.
The 29th of October was a significant date for Roman Byzantium in other ways. In 437, Valentinian III, Western Roman Emperor, married Licinia Eudoxia, daughter of his cousin Theodosius II, Eastern Roman Emperor, in Constantinople, unifying the two branches of the House of Theodosius. In 969, Byzantine troops overran and occupied Antioch, then part of Syria. Its ruins are now part of southern Turkey.
Reference: “Constantine the Great.” In The Grove Encyclopedia of Medieval Art and Architecture. Oxford University Press, 2012.