Diocletian was then hailed as emperor by the same army that almost defeated him and he marched towards Rome as victor. Soon after his arrival he named his friend Maximian as co-emperor giving him rule over the western half of the empire. Both would then select subordinates who were not relatives of their own to help in the task and secure a line of succession unlike a blood dynasty. Diocletian's vision of this governmental scheme became known as the Tetrarchy and the first cycle of which was completed, as far as he was concerned, when he abdicated in 305 and demanded Maximian do likewise to leave their subordinates to rule.
Modern historians with the gift of hindsight pinpoint Diocletian's choice of reforming the army as the key culprit of the empire's downfall almost 200 years later. He figured that rather than have weak concentrations of army outposts scattered over the length of the empire's borders it would be better to have a centralized large force which could respond quickly in the event of a military crisis. While the theory may have been sound in principle he never foresaw the obstacles that led to the successful deployment and logistical problems that this method required and, thus, over time Romans became increasingly susceptible to barbarian attacks.
Diocletian died an old, forgotten and heartbroken man in his retirement palace in what is now Croatia. In the end he was vilified for shattering the economy, wreaking political chaos in Rome and resorting to the now somewhat anachronistic practice of persecuting Christians. Finally, he had to witness in his own lifetime the utter failure of his power sharing format when the Tetrarchy disintegrated into the Constantinian dynasty.