Maximinus succeeds his uncle, Galerius, in 311, occupying Asia Minor.

The aged Diocletian has been living in retirement in the neighborhood of Salonae, on the edge of the Adriatic, where he has had a magnificent palace built (the modern town of Split, in Yugoslavia, occupies the site of its ruins).

He has seen his Tetrarchic system fail, torn by the selfish ambitions of his successors.

He has heard of Maximian's third claim to the throne, his forced suicide, his damnatio memoriae.

In his own palace, statues and portraits of his former companion emperor are torn down and destroyed.

Deep in despair and illness, Diocletian may have committed suicide.

The death of the former emperor on December 3, 311, occurs almost unnoticed.

Galerius, a ruthless ruler, has imposed the poll tax on the urban population, maintained the persecution of the Christians that Diocletian had initiated, and managed to hold together an empire riven by civil war in the West.

In the winter of 310-311, however, he becomes incapacitated with a painful disease.

On April 30, 311—perhaps fearing that his illness is the vengeance of the Christian God—he issues an edict grudgingly granting toleration.

Shortly afterward, he dies.

Licinius takes over Galerius' European dominions.

Maximinus had grudgingly accepted Galerius's edict of toleration for Christians but still endeavors to organize and revitalize paganism.

Cities and provinces are encouraged to petition for expulsion of Christians from their territories, and the Acts of Pilate, an anti-Christian forgery, is taught in the schools.

In the autumn of 312, Maximinus relaxes his persecutions somewhat, and shortly before his death in the following year will grant full toleration and the restoration of the confiscated church property.

Construction had begun in 308 on the Basilica of Maxentius and Constantine (sometimes known as the Basilica Nova 'new basilica' or Basilica Maxentius).

Completed in 312 by Constantine I after his defeat of Maxentius at the Battle of the Milvian Bridge, it is the largest building in the Roman Forum.

A marvel of Roman engineering work, it is at the time of construction the largest structure to be built and thus is a unique building taking both aspects from Roman baths as well as typical Roman basilicas.

At this time, it uses the most advanced engineering techniques known including innovations taken from the Markets of Trajan and the Baths of Diocletian.

Similar to many basilicas at the time such as the Basilica Ulpia, the Basilica Maxentius features a huge open space in the central nave, but unlike other basilicas instead of having columns support the ceiling the entire building has been built using arches, a much more common appearance in Roman baths than basilicas.

Another difference from traditional basilicas is the roof of the structure.

While traditional basilicas were built with a flat roof, the Basilica Maxentius is built with a folded roof, decreasing the overall weight of the structure and decreasing the horizontal forces exerted on the outer arches.

Maxentius recovers Africa in 311, but in the following year must face the invasion of Italy by his brother-in-law Constantine at the head of a forty thousand-man army.

Constantine, scoring victories at Milan and Turin against superior numbers, wins two more victories at Brescia and Verona, and then marches south on Rome, reinforcing his army along the way.

Before the beginning of his final battle with Maxentius, Constantine reportedly sees a flaming cross in the sky.

Adopting the cross as a symbol for the fight, he supposedly vows to become a Christian if he emerges victorious.

On October 28, 312, Constantine’s forces, now about fifty thousand strong, defeat Maxentius and his seventy-five thousand-man army outside Rome at the Milvian Bridge over the Tiber River, in which Maxentius drowns while attempting to escape.

Constantine thus removes a dangerous rival and secures his share in the new government organized by Licinius.

Constantine's adherence to Christianity is closely associated with his rise to power.

He had fought the Battle of the Milvian Bridge in the name of the Christian God, having received instructions in a dream to paint the Christian monogram on his troops' shields.

This, at least, is the account given by the Christian apologist Lucius Caecilius Firmianus Lactantius; a somewhat different version, offered by Eusebius of Caesarea, tells of a vision seen by Constantine during the campaign against Maxentius, in which the Christian sign appeared in the sky with the legend “In this sign, conquer.” Despite the Emperor's own authority for the account, given late in life to Eusebius, it is in general more problematic than the other; but a religious experience on the march from Gaul is suggested also by a pagan orator, who in a speech of 310 referred to a vision of Apollo received by Constantine at a shrine in Gaul.