‘Diocletian, if scrutinised with a critical eye, can be viewed as a magnificent individual, a most sympathetic character, who achieved great things through the conscious application of his intellect. The way in which he created anew the Empire, clearly falling apart at the time, demonstrates his genius as a first-class statesman.’ This quotation by Theodor Mommsen describes a Roman Emperor who by other historians, is seen as a source of barbarism, degeneracy and tyranny, or he even has been described by Eusebius as the scourge of God. Here is a military man, statesman and persecutor of Christians presented to us by a popular and expert historian.