The future Emperor Diocletian, originally named Diocles, grew up in Dalmatia in the territory of modern Montenegro and came from humble origins. It is believed that his father was a freedman, likely a scribe. Upon reaching the necessary age, Diocles joined the military as a common soldier and climbed to the upper echelons of the military hierarchy by the age of forty.
Diocletian became the last in the line of “soldier-emperors” during the crisis of the 3rd century. In 284 AD, Emperor Numerian died under mysterious circumstances on his return from a Persian campaign. The military arrested Numerian’s father-in-law, the suspect in his death, Praetorian Prefect Arrius Aper, and elected Diocles, who was then leading the protector corps (elite officers serving as the emperor’s bodyguards and a pool for high military positions), as the new emperor.