In the year 305. Diocletian resigned as emperor (as did the second Augustus, Maximian), and the new Augustus were Constantius Chlorus in the West and Galerius in the East.

After the death of Constantius Chlorus in 306, his legions proclaimed Constantine I Augustus. Constantine immediately informed Galerius, who appointed him ruler of Gaul, Britain, and Spain, but gave him only the title of Caesar, not Augustus.