Roman emperor

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The title of imperator, originally a military honorific, was usually used alongside caesar. Early emperors also used the title princeps ("first one") alongside other Republican titles, such as consul and pontifex maximus.

The legitimacy of an emperor's rule depended on his control of the Roman army and recognition by the Senate. Early emperors reigned alone, but later ones sometimes ruled with co-emperors. The office of emperor was seen as different from that of a rex ("king"). The first emperor, Augustus, refused to be called a monarch.

From Diocletian, emperors ruled in a more openly monarchic style. Constantine the Great moved the capital to Byzantium, later called Constantinople, in 330 AD. He was the first Christian emperor and believed the emperor was God's chosen ruler on earth. The Western Roman Empire ended in the late 5th century, but the Eastern Empire continued until the Fall of Constantinople in 1453.

Background and beginning

See also: Crisis of the Roman Republic

Modern historians see Augustus as the first Roman emperor, while Julius Caesar is seen as the last leader of the Roman Republic. Some Romans, however, thought Julius Caesar was the first emperor. Caesar took control of Rome but could not create a lasting system to keep his power. His rule came after a long decline in which powerful generals influenced the Republic.

By the end of the Republic, no special title showed who held the highest power. Julius Caesar held many important positions, like pontifex maximus and consul, and even became dictator in perpetuity. After his death, his grandnephew Octavian, whom Caesar named as his heir, took over. In January 27 BC, Octavian gave back some power to Rome's Senate but kept control for himself. The Senate called him princeps and gave him the title augustus, meaning "elevated." This title became the main name for Roman emperors. Most historians mark 27 BC as the start of the Roman Empire, even though the Republic had already ended years before.

Powers under the Principate

The Roman emperor had special powers that came from combining many different roles and duties that were once shared among several leaders. Augustus, the first emperor, held all these powers himself without time limits, even if some were meant to last only a year. He was often elected to important jobs like consulship and censorship. This time period is called the "Principate" because the emperors used the title princeps, meaning "first one."

The most important powers of the emperor were his command power (imperium maius) and tribunician power (tribunicia potestas). Before becoming emperor, Augustus gained control over all troops by getting command power, which made him stronger than other military leaders like the proconsuls and even allies such as Agrippa. The tribunician power, which he started using in 23 BC, let him act like a tribune of the plebs without actually being one. This meant he could protect the common people, stop any decision made by leaders, suggest new laws, and call meetings of the Senate. This power was very stable and important because it was renewed every year.

The emperor also had control over religious matters, which led to the creation of a special worship cult. Augustus became the chief priest, known as pontifex maximus, in 12 BC. Later emperors used a different title, pontifex inclytus, meaning "honorable pontiff." The last emperors known to have used the title pontifex maximus were Valentinian III and Marcian in the 5th century.

The only surviving document that directly describes an emperor's powers is the Lex de imperio Vespasiani, written after Emperor Vespasian took power in 69. It says he could make treaties, hold Senate meetings, propose laws, support election candidates, expand city borders, and use special powers when needed. It also states that he was not bound by laws and that his earlier actions were considered legal. The document does not mention specific powers like imperium or tribunicia potestas, but they were likely included earlier. The title "emperor" was not used in the document, showing that the imperial titles were tied to the person himself.

Succession and legitimacy

The Roman emperors did not have a clear way to decide who would be the next ruler. Instead of naming a successor, they often adopted their best candidate as a son and heir. For example, Tiberius married Julia the Elder to become Augustus's son-in-law.

Vespasian was the first to openly name his sons Titus and Domitian as heirs. After Domitian’s death, the Senate chose Nerva as emperor, starting the Antonine dynasty. Marcus Aurelius ruled with his adoptive brother Lucius Verus and later with his son Commodus.

There were often fights over who should be emperor, and many rulers faced civil wars. Being seen as a true emperor usually depended on being accepted by the Roman army and sometimes the Senate. Even those who started as rivals could later be seen as legitimate rulers if they gained enough support.

Later developments

The period after the rule of the early emperors is called the Dominate, named after the title dominus ("lord") used by Diocletian. During this time, emperors held absolute power, and their rule became more like a monarchy. Emperors started wearing the diadem crown as a main symbol of their power.

As time went on, the Roman Empire faced many challenges. The Empire had grown very large, which caused political and economic problems. The period known as the Pax Romana ("Roman peace") ended during the rule of Commodus. After Commodus's death, Septimius Severus became emperor. During his rule, the army became more powerful, and emperors often relied on military support. The murder of Severus Alexander led to a 50-year period called the Crisis of the Third Century, nearly ending the Roman Empire. The Senate tried to take control by choosing new emperors, but stability returned when Diocletian reunited the Empire in 285.

Diocletian made many changes to bring stability. He created the Tetrarchy, a system with four leaders: two main emperors (augusti) and two heirs (caesares). Each pair ruled half of the Empire, creating a Western and an Eastern Roman Empire. Diocletian also claimed his rule was supported by divine power, calling himself the son of Jupiter.

Emperors no longer needed the Senate's approval, and they became the sole source of law. The Senate's role became less important, though some traditions continued. Some emperors were very young, like Gratian, who became emperor at age 8. These young rulers shared the title but not the actual power.

Diocletian's system did not last after he retired in 305. Constantine I reunited the Empire in 324 and established hereditary succession. He was the first emperor to convert to Christianity, and later emperors saw themselves as protectors of the Church. The Empire remained divided into Western and Eastern parts.

The Western part eventually weakened, with emperors often controlled by military leaders. In 476, the last Western emperor, Romulus Augustulus, was overthrown, marking the end of the Western Roman Empire. The Eastern part, however, continued for another thousand years.

Titles

Imperator

Main article: Imperator

The title imperator means "to command" and dates back to the Roman Republic. Soldiers gave this title to successful commanders. Later, it became a special honor, and the commander kept the title until the end of their time in office. The first person known to use imperator was Aemilius Paulus in 189 BC. Important leaders like Pompey, Sulla, and Julius Caesar were also called imperator. Over time, the title changed to mean the highest power.

Augustus used Imperator instead of his first name, becoming Imperator Caesar. After Nero, nearly all emperors used the title imperator. By the time of Vespasian, it had become the main way to call the ruler.

Caesar

Main article: Caesar (title)

Originally, Caesar was the family name of Gaius Julius Caesar. Augustus used it as a family name, calling himself Imp. Caesar. After Nero died, the new emperor Galba added Caesar to his name. Later, Caesar came to mean the heir to the throne. The title lost importance over time, especially after Constantine I. In some places, words like Kaiser in Germany and Tsar in Russia come from Caesar.

Augustus

Main article: Augustus (title)

The title Augustus was given to Octavian in 27 BC. It was a special and honorable name, connected to religious practices. All emperors after Octavian used this title. In the East, it was translated as Sebastos, but later Augoustos became more common. In the West, leaders like Charlemagne also used the title.

Princeps

Main article: Princeps

The word princeps means "first". Early emperors used this title to show they were continuing the Republic. It was an honorific title without special powers. Augustus liked to use it because it suggested equality rather than control. Later, the title dominus ("lord") replaced princeps, showing a change in how the empire was ruled.

Basileus and autokrator

Main article: Basileus

Basileus is a Greek word for monarchs. Heraclius first used it officially in 629 after winning a war. Later, the full title became "basileus and autokrator of the Romans". Foreign rulers were called different names, but Eastern emperors sometimes had to recognize other leaders as basileus.

Later assertions to the title

Main articles: Succession of the Roman Empire and Succession to the Byzantine Empire

After Rome was overthrown, Odoacer did not claim to be emperor. His successor, Theodoric the Great, acted almost like an emperor but used the title rex. He also used the old title princeps and tried to act like the old emperors. He even asked for special items from the eastern emperor.

Two rebels, Burdunellus and Peter, were called "tyrants" by some, which might mean they wanted to be emperor, but little is known about them. A leader named Masties from the Berber people claimed to be imperator after 476, saying he ruled both Romans and Maurians. The last try to bring back the emperor in the West happened when the Goths asked Belisarius to be emperor during the Siege of Ravenna, but he said no.

Number of emperors

Different writers in ancient times tried to count how many Roman emperors there were, but they came up with different numbers. One writer from the 4th century said there were 43 emperors from Octavian Caesar Augustus to Jovian. Another writer from the 6th century called Diocletian the 33rd emperor, and if you add the other emperors they mention, you get 41 emperors up until Constantine I.

Some writers also made their own lists of emperors. One from the 4th century listed 58 emperors, while another listed 44, and a later writer listed 46. These numbers differ because there was no clear rule to decide which emperors counted and which did not. Some emperors ruled for very short times or had little effect, so they were often left out of the histories.