Owing to his vices and incapacity he was left out of account in the division of the empire which took place in 305. A variety of causes, however, had produced strong dissatisfaction at Rome with many of the arrangements established by Diocletian, and on October 28, 306, the public discontent expressed itself in the massacre of those magistrates who remained loyal to Flavius Valerius Severus and in the election of Maxentius to the imperial dignity. He was supported by the Praetorian Guard.
With the help of his father, Maxentius was enabled to put Severus to death and to repel the invasion of Galerius; his next steps were first to banish Maximian, and then, after achieving a military success in Africa against the rebellious governor, Domitius Alexander, to declare war against Constantine as having brought about the death of his father Maximian. His intention of carrying the war into Gaul was anticipated by Constantine, who marched into Italy.
He was a man of brutal and worthless character; but although Gibbon's statement that he was "just, humane and even partial towards the afflicted Christians" may be exaggerated, it is probable that he never exhibited any special hostility towards them.