Roman emperors ruled over the Imperial Roman Empire starting with Augustus from 27 BCE and continuing in the Western Roman Empire until the late 5th century CE and in the Eastern Roman Empire up to the mid-15th century CE. The emperors would take different titles such as Caesar and Imperator but it was always their command of the army which allowed them to keep their seat on one of history's most prestigious and long-lasting thrones.
Prior to the birth of the Roman Empire in the latter part of the first century BCE, there had existed many empires among these were the Assyrian, the Babylonian, the Persian, and the Macedonian. All of these had great leaders such as Cyrus, Darius, Xerxes, and, of course, Alexander the Great. Yet, history tells us these great men were all called kings; the term emperor was never used. In contrast, the Roman Empire was different, for it didn't have a king; it had an emperor, and one must search both the Roman Republic and the Empire, almost one thousand years of history, to discover the reasons for the difference.
From The Republic to The Imperial Era
Before Rome was an empire, it was a republic with a long history of “democratic” rule. After ousting the Etruscans and their king, the city-state was ruled by a Senate and/or an assembly with elected magistrates - consuls and tribunes, both with a term of office limitations. After conquering the Italian peninsula, Rome gained considerable land through an aggressive military campaign - primarily in North Africa, Spain, Macedonia and Greece, plus various islands throughout the Mediterranean. Unfortunately, the size of the Republic placed considerable strain on its leadership; leaders, good and bad, rose through the political and military ranks to gain power, men such as Sulla, Gaius, Pompey and finally Julius Caesar; the latter would assume the ominous title of “dictator for life.” As one historian noted, various social, political, and economic forces could no longer be contained by the Republican leadership; change was inevitable. After the assassination of Julius Caesar by members of the Senate on the Ides of March, a battle, both political and military, ensued between the members of the so-called Second Triumvirate (Octavian, Mark Antony and Lepidus) with Octavian becoming the eventual victor.
The First Emperor
As a victorious general, Octavian had often heard the cries of his soldiers - “Imperator” - especially after his defeat of Mark Antony. In the future, this title would automatically be assumed by his successors, regardless of their military experience, upon their ascension to the imperial throne. After two decades of civil war, Octavian, the adopted son of Julius Caesar, returned to Rome a hero. The people celebrated, hoping for the return of the stability that had been the Republic. While initially shying away from honors and power, Octavian, who would soon become known by the name of Augustus (a name meaning “sacred” or “revered”), would increasingly assume authority far beyond the intent of the Senate who had inadvertently granted it. One historian raised the question: was Augustus a “tyrant” who quietly took away Roman liberty, or a generous statesman who shared power with the Senate with the consent of the people of Rome? As an emperor, Augustus would set the stage for all of those who would follow him, from Tiberius, his much-maligned stepson, through the corruption of Caligula and Nero, the cruelty and incompetence of Domitian, and lastly, to the final individual to be called a Roman emperor, Romulus Augustalus (oddly named for one of the mythical founders of the city and the empire's first emperor).
While many of the structures that had existed under the old Republic remained, such as the Senate, they existed in name only. In a kingdom, a king had to answer to an assembly (England had a Parliament; France had the Estates General, for example). Often, these assemblies controlled the finances of the kingdom, but in Rome the emperor could collect and spend as he wished. Emperor Nero, always in need of funds, would cry conspiracy, seize the property of an unsuspecting senator and murder him. After Augustus the Senate would never again have any real authority - only to endorse the wishes of the emperor. While Augustus and his successors would treat them with a modicum of respect (most wanted to avoid a repeat of the Ides of March) the real power was in the hands of the emperor, and to ensure his own safety, he relied on his personal bodyguard – the Praetorian Guard, who, within a few decades, would wield power unforeseen even by the Emperor Augustus.
With the consent of the Senate, Augustus slowly assumed the sole leadership of the Empire, and while he disliked titles (even the title of emperor); he took instead the title of “princeps” meaning “first citizen.” Initially, he was a consul (a position other emperors would also hold) and provincial governor (of Gaul, Syria, Egypt and Cyprus, the latter gave him control of a majority of the military); as emperor he would command twenty-six legions. The Senate bestowed on him, and thereby his successors, certain powers for life: imperium maius, extreme authority over the provincial governors; and tribunicia potestas or tribune of the plebs, the authority to call an assembly of the people to enact laws. With his new powers, he could veto the actions of the magistrates (whom he would later appoint), and, in order to control those around him, he controlled the imperial patronage - no one could “run” for office without his consent. He also interfered with the religion of the empire. He rebuilt decaying temples, resurrected old religious ceremonies and assumed the title of Pontifex Maximus or Chief Priest. In short, the emperor's word became law.
However, despite his growing power, he remained popular with the people through his continuous supply of grain, games (he even presided over them) and numerous rebuilding projects. In his The Twelve Caesars, historian Suetonius wrote that the emperor improved the overall appearance of the city. “I found Rome built of sun-dried bricks; I leave her clothed in marble.” Those who followed Augustus would continue to rebuild the city, especially her temples, aqueducts, and arenas. Many Roman citizens believed they were entering a new golden age.
The Imperial Dynasties
Augustus (31 BCE to 14 CE) maintained control of the empire, even in death, and, like a king, named his successor. In his case it was Tiberius. Even the name Augustus would become a title, assumed by all who followed him. But the naming of a successor is one of the few ways an emperor is like a king. In a kingdom, the tradition was for the continuation of a bloodline. The present queen of England is from the House of Windsor and can trace her ancestry through the Hanoverians, Stuarts, Tudors, and even the Plantagenets. In contrast, the last emperor of the Roman Empire wasn't even related to his predecessor let alone Augustus. In fact, only a handful of emperors were related by blood. Titus and Domitian were the sons of Vespasian while Commodus was the son of Marcus Aurelius. Others were adopted - Tiberius, Nero, Nerva, Trajan, and Marcus Aurelius. Some obtained the throne through conquest or murder - Galba, Otho, Vitellius, Vespasian and Macrinus. One even bought the throne - Didius Julianus. Surprisingly, some emperors never set foot in Rome - Macrinus and Maximinius, while at times, there might be more than one claimant such as in the Year of the Five Emperors.
However an individual obtained the throne, the power that went with the position remained. And, at the forefront of this power was the Praetorian Guard. While the authority of the empire lay in the hands of the emperor, he placed his life in the hands of the Guard. During bleak times, the Praetorian Guard would be the ones to pick and choose (and sometimes overthrow) an emperor. After the death of Caligula at the hands of the Praetorian Guard, they found Claudius cowering behind a curtain and hurried him to the Senate, who reluctantly proclaimed him emperor. When they had finally realized the ineptness and depravity of Elagabalus, they murdered him and his mother and declared Alexander Severus the new emperor.
Unfortunately, the life of an emperor would not always be filled attending lavish ceremonies, directing military campaigns and dictating laws. He would often sit on the throne, paranoid, fearful of those closest to him. Of the first twelve emperors - Augustus through to Nerva - four would die naturally (although some question one or two of these), four would be assassinated, two would commit suicide, and two would be murdered by poison or suffocation, as one historian put it, “supreme power brought supreme risk.” It was rare that an emperor would resign or die a natural death as the possibility of being overthrown always existed.
The autocratic power of the emperor would endure despite the destructive reigns of Caligula, Nero, Commodus, and Elagabalus. Luckily for the empire, it would see the strength of such men as Vespasian, Trajan, Marcus Aurelius, and Constantine; territories would be gained and lost; the empire would expand and contract, but somehow, despite the good and bad, the empire would continue to survive.
The emperor held a special place in the hearts and minds of the people of Rome, both in life and in death. This adoration for the imperial leader would lead to his eventual deification or apotheosis. However, this type of honor or Imperial Cult was not unique to Rome; it dated back to Alexander the Great - he considered himself not the son of Phillip II but the son of Zeus. Emperor Augustus was treated as a deity during his reign; altars and temples were built to honor him throughout the empire - Pergamum, Lyons, and Athens - but none were built in Rome (at least while he still lived). Although he may have considered himself the son of a god, he never permitted himself to be called a god. Upon his death, the Senate would deify him - the same would happen to many of those who followed him, for example, Antonius Pius, Hadrian, Marcus Aurelius, Trajan and Alexander Severus. Often, an emperor would initiate the deification of his predecessor. Unfortunately, emperors such as Tiberius, Caligula, Nero, Commodus, and Elagabalus were considered too “odious” to receive the honor. Caligula and Nero both considered themselves gods while they were still alive, and Commodus thought he was actually the reincarnation of Hercules.
Division of the Empire
After a long period of truly incompetent emperors, Diocletian came to power in 284 CE. The Pax Romana or Roman peace had been dead for over one hundred years. The empire was being attacked on all sides and it was on the verge of collapse. Diocletian realized the one major flaw of the empire - its size. To solve the problem he created the tetarchy or rule of four. He divided the empire into two parts, one with its capital at Rome and another with its capital as Nicomedia (it would later be moved to Byzantium or Constantinople by Emperor Constantine). The principate initiated by Augustus was replaced by the dominate, however, he strengthened the borders, developed a more efficient bureaucracy, and stabilized the economy. Unfortunately, as the eastern half of the empire flourished, the west declined, even the city of Rome fell into ruin, until, finally, in 476 CE, the last emperor surrendered. The city's conqueror, Odoacer, refused the title of emperor.
For the most part, the people of the Roman Empire were kept reasonably happy, even during times of duress, as long as the emperors provided grain for bread and games/entertainment. Lasting monuments were built to honor many of the emperors - the Baths of Caracalla and Nero, the Arch of Constantine, and Trajan's Column. The emperor was an absolute ruler who provided stability for the people. It was never a constitutional office, quite simply, the emperor was the law.