Conference of Carnuntum

The Conference of Carnuntum was a gathering of ancient Roman rulers on 11 November 308, intended to stabilize the power-sharing arrangement known as the Tetrarchy. It was convened by the Eastern augustus (emperor) Galerius (r. 305–311) in the city of Carnuntum (present-day Petronell-Carnuntum, Austria), which at the time was located in the Roman province of Pannonia Prima. A dispute over the title of augustus in the West had been ongoing since the previous year, when consecutive invasions by Severus II (r. 306–307) and Galerius had failed to recover Italy from the usurpers Maxentius (r. 306–312) and Maximian (r. 286–305, 306–308). Present at the conference were the retired Diocletian (r. 284–305), and his former colleague, Maximian.

According to deliberations at the meeting, Maximian was to retire permanently from his imperial position; Licinius (r. 308–324), a former general of Galerius, was raised as the western Augustus and was to deal with Maxentius, who had been treated as an usurper; and Constantine (r. 306–337) was relegated, for the second time, to western caesar. These decisions, however, did not please most of them: Constantine questioned his demotion and persisted in using the style of augustus; Maximinus (r. 305–313) demanded promotion from Galerius; Maximian would not be satisfied with his demotion and would attempt one last conspiracy, in 310, at the court of Constantine in Arles, while Licinius would do nothing in the following years to stop Maxentius.