Diocletian

Diocletian was a Roman emperor who ruled from 284 until he stepped down in 305. He was born into a family of low status in the Roman province of Dalmatia. He rose through the military ranks, serving under emperors like Aurelian and Probus. After the deaths of Emperor Carus and his son Numerian, Diocletian was proclaimed emperor by his troops.

His reign brought stability to the Roman Empire during a time known as the Crisis of the Third Century. He split the empire into two parts. He ruled the Eastern Empire while his colleague Maximian ruled the West. Together with two junior emperors, Galerius and Constantius, they formed a system called the Tetrarchy to govern the empire better.

Diocletian strengthened the empire's borders and organized its government. He also introduced important tax reforms. After stepping down from power, he retired to his palace on the Dalmatian coast, where he tended to his gardens. His palace later became the foundation of the modern city of Split in Croatia.

Early life

Diocletian was born in Dalmatia, near the town of Salona (now Solin, Croatia). His birth name was Diocles, and he came from a family of low status. Not much is known about the first forty years of his life. He served under the emperors Aurelian and Probus and became a commander of elite cavalry for Emperor Carus.

After the death of Carus's son Numerian, Diocletian was chosen by the army to be the new emperor. He took the name Diocletianus and became emperor in 284. He later defeated another claimant to the throne, Carinus, in battle and became the sole ruler of the Roman Empire.

Early rule

Diocletian began his rule during a difficult time for the Roman Empire. He became emperor in 284 after moving up through the military. He faced many challenges, including conflicts with tribes like the Quadi and Marcomanni.

To better manage the large empire, Diocletian created a system where two emperors ruled together. He chose a fellow officer named Maximian to be his co-ruler. This helped share the work and brought stability. The two emperors even took on symbolic names linked to gods—Diocletian as Jovius and Maximian as Herculius—to show their leadership roles.

Diocletian also dealt with threats from tribes such as the Sarmatians and worked on peace agreements with Persia. These efforts helped protect the empire’s borders and keep trade routes safe. His rule brought important changes that shaped the future of the Roman Empire.

Tetrarchy

See also: Tetrarchy

Foundation of the Tetrarchy

After returning, Diocletian gave command of the war against Carausius to Flavius Constantius. Constantius ended the war in 296. He was a military leader with experience from Aurelian's campaigns against Zenobia. On March 1, 293, in Milan, Constantius became a leader called a Caesar. The same day, Diocletian named Galerius Maximianus as another leader in Philippopolis or Sirmium. Constantius was in charge of Gaul and Britain, while Galerius was in charge of Syria, Palestine, Egypt, and the eastern lands.

This system was called the Tetrarchy, meaning rule by four. The leaders were connected by family ties. Diocletian and another leader were called brothers, and they adopted Galerius and Constantius as their sons. This set up a way to pass power in the future. Galerius and Constantius would take over after Diocletian and the other leader stepped down. Later, the sons of Galerius and Constantius would become leaders too. To prepare them, Diocletian brought the sons, Constantine and Maxentius, to live at his court in Nicomedia.

Conflict in the Balkans and Egypt

In the spring of 293, Diocletian travelled with Galerius from Sirmium to Byzantium. After that, he stayed in Sirmium for the winter and spring. He fought the Sarmatians in 294 and built forts along the Danube River. In 295 and 296, he fought the Carpi people and won. Later, Galerius also fought successfully on the Danube.

Galerius was busy in Upper Egypt from 291 to 293, dealing with local troubles. He went back to Syria in 295 to face the Persian empire. In Egypt, Diocletian's changes to taxes caused anger, and a rebellion began after Galerius left. The rebel Domitius Domitianus called himself a leader in 297. Diocletian went to Egypt to stop the rebellion. He secured the countryside, but Alexandria kept fighting until March 298. After that, Diocletian made sure Egypt followed Roman rules more closely.

Diocletian travelled down the Nile River, visiting places like Oxyrhynchus and Elephantine. He made peace with the Nobatae and Blemmyes tribes in Nubia. Then he left Egypt and met Galerius in Mesopotamia.

War with Persia

See also: Roman–Iranian relations and Roman–Persian Wars

Invasion, counterinvasion

In 294, Narseh became the leader of Persia. He started a war with Rome in 295 or 296. He first attacked Armenia and then moved into Roman lands in Mesopotamia in 297. There, he defeated Galerius in a battle. Diocletian made it seem like Galerius was to blame and not himself.

Galerius got more soldiers and attacked back in 298. Narseh stayed in Armenia, which was good for the Roman soldiers but not for the Persian horse soldiers. Galerius won two big battles against Narseh. In the second battle, Roman soldiers took Narseh's camp, treasures, and family. Galerius moved down to the city of Ctesiphon before going back to Roman lands.

Peace negotiations

Narseh asked Galerius to return his family during the war, but Galerius refused. Peace talks started in spring of 299. The peace agreement gave Armenia back to Roman control. Other areas also came under Roman influence, helping to spread Syriac Christianity in the future.

Diocletian built a fortified road on the southern border to strengthen defenses, but it didn’t work well against big armies.

Religious persecutions

Diocletian and his co-emperor Galerius thought Christians were causing trouble. They wanted Christians to follow old Roman ways to fix things. Special readers of signs agreed that Christians were the problem.

Because of this, Diocletian made rules to stop Christians from meeting and to take away their holy books. He also destroyed their meeting places. Some Christians were hurt or punished for not following these rules. Still, many Christians kept their beliefs. Later leaders changed these rules, and Christianity became more accepted in the empire.

Later life

Diocletian entered Rome in the winter of 303. He celebrated big events, including the 20th anniversary of his rule and a victory in war with Persia. But he became unhappy because the Romans did not show him enough respect. He left Rome in December and did not finish all his work there.

Later, while on a military trip, Diocletian became very sick. By late 304, he was too weak to appear in public. In 305, he decided to give up his job as emperor. He told his soldiers he was too tired and needed to rest, and that it was time for someone stronger to take over. This made him the first Roman emperor to step down on his own.

After stepping down, Diocletian went back to his home region of Dalmatia. He lived in a large, fortified palace near the town of Spalatum, which is now part of the city of Split in Croatia. Even after retiring, he stayed in touch with his co-emperor Maximian. Diocletian lived quietly in his palace gardens for several years. He saw his system of shared rule fall apart due to conflicts among his successors. He passed away in 311 or 312 after an illness.

Reforms

Diocletian wanted to make the Roman Empire stable and peaceful. He made big changes to the government to make it stronger and led by the emperor. Cities like Milan, Trier, Arles, Sirmium, Serdica, Thessaloniki, Nicomedia, and Antioch became important places. Diocletian wore fancy clothes and people had to show him respect.

He changed how the government worked by giving each person a clear job. He added more workers to handle taxes and laws and split the empire into smaller parts. He also changed how judges worked and made sure laws were written down clearly.

To keep the empire safe, Diocletian built stronger forts and moved soldiers to new places. He made the army bigger but needed more money, so he found new ways to collect taxes from landowners. He also tried to control prices to stop things from getting too expensive, but this did not work well.

Legacy

See also: Dominate

Diocletian was special because he ruled for twenty-one years and then chose to step down. He lived the rest of his life in peace. He was one of the few Roman emperors to pass away naturally and the first to retire on his own. After he left, his system of sharing power fell apart, and the empire faced many fights among leaders. Peace returned when Constantine won in 324.

Constantine kept some of Diocletian's good ideas, like strong borders and better government rules. He also stopped Diocletian's strict rules against Christians and made Christianity important in the empire.

Even after Diocletian’s time, some of his changes stayed for many years. His way of organizing taxes and managing the empire helped shape many places in Europe. A special way of counting years in some churches started from the year Diocletian began his rule. In stories from Serbia and Jewish traditions, Diocletian is remembered in different ways.