Cassius Dio – History, Major Works & Facts about one of Rome’s Greatest Historians

Cassius Dio – history and major works

Cassius Dio was a Greek-born Roman politician and historian. While he was an accomplished politician, he is best known for capturing Rome’s history in his 80-volume book “Roman History.” About one-third of “Roman History” has survived throughout the world’s history and many contemporary historians and scholars rely on his book to learn more about life in Ancient Rome.

Read more about this famous Roman historian, including his background and thoughts on some of Rome’s most famous rulers.

Background: Family & Career in Politics

Cassius Dio hailed from Nicaea, Bithynia (modern-day Turkey) and was a member of a prominent family. His father, Cassius Apronianus, was a respected public servant. Apronianus occupied senatorial positions, as well as served as governor of a number of regions in Asia Minor.

Growing up, Cassius learned how to speak Greek and Latin. He moved to Rome around 180 AD when he was in his early teens. He would later spend the rest of his life working in the Roman public office.

By the time he was 25, he had started working as quaestor. A questor in ancient Rome was a junior magistrate who served in the treasury department.

Cassius also held several positions under various Roman emperors; for example, he was a praetor and consul under Septimius Severus, he also joined Emperor Caracalla on a tour of the east, and Emperor Macrinus appointed him curator of Pergamon and Smyrna.

Having distinguished himself in his previous positions, he went on to work in Africa as a proconsul and later a legate in the regions of Dalmatia and Upper Pannonia. During the reign of Emperor Alexander Severus, he became a consul for the second time.

Writing “Roman History”

Cassius started writing extensively in the 190s AD. Of his many writings, he is perhaps best known for authoring “Roman History”, which is an 80-volume book that details the events of Rome, from its early years down to the reign of Alexander Severus.

He wrote about Roman mythology, the story of Aeneas, who is regarded as Rome’s first hero. The historian also penned works on the birth of Rome by Romulus. Cassius Dio was known for writing the historical events that took place during the British revolt (led by Queen Boudica) against Rome’s rule in Britannia around 60 AD.

Cassius wrote “Roman History” in Attic Greek, and it took him ten years to research and an additional twelve years of writing to complete the book. Most of his works got lost throughout the course of time. Fortunately, other Byzantine authors like Xiphilinus and Zonares captured certain events that occurred between 69-46 BC that would have otherwise been lost.

It is evident that Cassius borrowed extensively from Thucydides, who was a Greek historian. He was able to enrich his works by sourcing for information from public records and other literary works, especially for events that preceded him.

For events that he had witnessed, Cassius often wrote from his personal experiences, and it was obviously based on his comments (negative and positive) on the emperors that ruled during that period. Some of the notable Roman leaders he wrote on included Pertinax, Septimus Severus, Geta, and Alexander Severus.

Cassius Dio’s views on Roman Emperors

Cassius stated in his “Roman History” that Rome’s Imperial Period started from 31 BC, which was different from what his contemporaries had written in their books. Where the historian believed the empire to have started with Octavian (the heir of Julius Caesar), the others preferred to cite Caesar’s authoritarian rule, which began around 45 BC, as the start of the Roman Empire.

Cassius defended his decision saying that Rome’s system of governance changed from a republic to a monarchy following the events of Caesar’s death. The transition into an empire featured heavily in his writings. He also wrote positively about the reign of Rome’s first emperor, i.e. Octavian (later Augustus).

Some of his writings were full of praises for Emperor Claudius, especially for his intelligence and passion for the arts. Other emperors that received positive comments from the historian included Pertinax and Marcus Aurelius. But he was also critical of Rome’s rulers like Elagabulus and disapproved of his eccentric lifestyle.

Perhaps the emperors to receive the harshest criticism from Cassius were Nero and Commodus. He accused Nero of murdering his mother, stating that the emperor paid his Praetorian Guard to carry out other criminal activities. In Cassius Dio’s works, Emperor Nero was accused of starting a fire that destroyed most of Rome.

For Commodus, Cassius called him guileless, cruel, and a coward. He wrote about the emperor’s desire for killing animals, further adding that he had witnessed Commodus kill an ostrich and victoriously posing like a gladiator. Cassius struggled to hold his laughter in and wrote that the emperor’s death brought some relief.

Cassius had a close relationship with Emperor Septimius Severus, but he didn’t let their friendship bar him from criticizing the ruler. While he praised Severus for his intelligence and hard work, he also spoke against the emperor’s mistreatment of the Senate.

The last ruler he wrote about was Alexander Severus. Though it was brief, he recorded some of the challenges that the emperor faced during his reign from 222 to 235.


While the date of Cassius’s death remains unknown, it’s likely that it occurred after 229 AD.

Did you know?

  • It took Cassius Dio about 22 years to complete “Roman History.” The famous work covers over 1,000 years of Rome’s history!

  • Apart from rulers, he also wrote about other public figures and foreigners that influenced Rome, including the Egyptian queen Cleopatra. Cassius described her as a beautiful and very intelligent woman who was also manipulative and scheming.

  • Cassius Dio has appeared in modern popular culture. In 2017, he was portrayed by actor Edwin Wright in the mini-series “Roman Empire: Reign of Blood.”

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