Diocletian was one of the most influential Roman emperors in history. He rose from humble origins to become the ruler of a vast empire that stretched from Britain to Egypt. He is best known for his reforms that stabilized the empire after a century of chaos and crisis. He also initiated the last and most severe persecution of Christians in Roman history.

Diocletian was born as Diocles in the province of Dalmatia, in modern-day Croatia, around 245 CE. His father was a scribe or a freed slave of a senator. He joined the Roman army as a young man and proved himself as a capable and loyal soldier. He served under several emperors, including Carus and his sons Carinus and Numerian. In 284 CE, he was proclaimed emperor by his troops after Numerian was found dead in mysterious circumstances. He adopted the name Diocletianus and defeated Carinus, who claimed the throne in the west, at the Battle of the Margus.

Diocletian realized that the Roman Empire was too large and complex to be governed by one man. He decided to divide it into two halves, each ruled by an Augustus (senior emperor) with a Caesar (junior emperor) as his deputy. In 286 CE, he appointed his friend and fellow soldier Maximian as Augustus of the west, while he retained control of the east. In 293 CE, he further subdivided the empire into four parts, creating the Tetrarchy (rule of four). He chose Galerius and Constantius Chlorus as Caesars for the east and west respectively. Each tetrarch had his own capital, army, administration, and coinage. The tetrarchs were supposed to cooperate and rotate power every 20 years.

Diocletian’s reforms restored order and efficiency to the empire. He reorganized the provinces, increased the size and discipline of the army, reformed the taxation system, and regulated prices and wages. He also strengthened the borders and waged successful wars against various enemies, such as the Sarmatians, Carpi, Alamanni, and Sassanids. He built many public works, such as roads, bridges, aqueducts, temples, and palaces. He also enhanced his own authority and prestige by adopting elaborate rituals and titles that emphasized his divine status and absolute power.

Diocletian’s policies were not welcomed by everyone. He faced several rebellions and usurpations from within and outside the empire. He also alienated many Christians by launching a systematic persecution against them in 303 CE. He ordered the destruction of churches, scriptures, and relics, as well as the imprisonment, torture, and execution of clergy and laity who refused to sacrifice to the pagan gods. The persecution lasted until 311 CE and resulted in thousands of martyrs and apostates.

Diocletian was the first Roman emperor to voluntarily abdicate his throne. In 305 CE, he announced his retirement along with Maximian and appointed Galerius and Constantius Chlorus as new Augusti. He retired to his palace in Salona (modern-day Split), where he spent his last years tending his gardens and writing his memoirs. He died in 311 or 312 CE, possibly by suicide or illness. His legacy was mixed: he saved the empire from collapse but also paved the way for its eventual division into two rival states.