Roman Emperor Caracalla is assassinated. He is succeeded by his Praetorian Guard prefect, Marcus Opellius Macrinus.

The Roman emperor stood as the paramount ruler of the vast Roman Empire throughout its imperial period. This era famously commenced with the elevation of Octavian, who was granted the revered title of Augustus in 27 BC, marking a pivotal transition from Republic to Empire. Over the centuries, these powerful figures utilized a diverse array of titles to underscore their authority and legitimacy.

When we refer to a Roman becoming "emperor" in English, it most frequently signifies their adoption of the title Augustus, a name that eventually evolved into Basileus in the Eastern Empire. Other significant titles included Caesar, commonly reserved for heirs-apparent, and Imperator, which originated as a military honorific for victorious commanders. Early emperors also skillfully employed the modest-sounding title princeps civitatis, meaning 'first citizen,' a deliberate choice to align themselves with the traditional republican ethos. Furthermore, emperors often accumulated various republican offices and distinctions, notably princeps senatus (leader of the Senate), consul (one of the two chief magistrates of the Republic), and pontifex maximus (chief priest).

The Nature of Imperial Rule: Legitimacy and Evolution

Acquiring and Maintaining Power

The very foundation of an emperor's legitimacy rested on a delicate balance: his undeniable control over the formidable Roman army and, critically, recognition by the venerable Roman Senate. Typically, an emperor would first be proclaimed by his loyal troops, often on the battlefield or in a province, and subsequently, the Senate would bestow upon him the necessary imperial titles, or sometimes both events would occur in tandem. While the earliest emperors initially reigned alone, a practice of co-emperors eventually emerged, allowing for the division of the empire's vast administration, particularly as its size and complexity grew.

The Roman Aversion to Kingship

A crucial distinction in Roman political thought was the clear separation between the office of emperor and that of a king. The Romans harbored a deep-seated historical aversion to kingship, a sentiment stemming from the tyrannical rule of the early kings of Rome that led to the establishment of the Republic. Augustus, the first emperor, was acutely aware of this historical context and resolutely refused any recognition as a monarch, carefully crafting an image as the "first citizen" rather than an absolute ruler. For the initial three centuries of the imperial period, from Augustus's reign up to the reforms of Diocletian, concerted efforts were made to present emperors as leaders of a continuing Republic, meticulously avoiding any association with the despised kings of Rome.

From Principate to Dominat: An Open Monarchy Emerges

This carefully maintained republican façade began to erode with the ascension of Diocletian. His profound tetrarchic reforms, which also saw the empire divided into administrative halves with one emperor in the West and another in the East, ushered in an era where emperors ruled in a much more openly monarchic style. The nominal principle of a republic was no longer upheld, yet the careful contrast with "kings" persisted. While imperial succession became generally hereditary, it was not automatic; it depended on the presence of a suitable candidate who was acceptable to both the powerful army and the extensive bureaucracy. Therefore, a principle of automatic inheritance, akin to traditional monarchies, was never fully adopted. Intriguingly, even after the eventual collapse of the Western Roman Empire, significant elements of the republican institutional framework, such as the Senate, consuls, and various magistrates, continued to be preserved in some form, particularly in the East.

The Empire's Shifting Capitals and Enduring Legacy

The Rise of Constantinople and the Division of Power

A momentous shift occurred during the reign of Constantine the Great, who in 330 AD, chose to relocate the empire's capital, the "Caput Mundi," from Rome to Constantinople, a city previously known as Byzantium. This move had profound long-term implications, signaling a new cultural and political center for the empire. The Western Roman Empire, weakened by internal strife and economic pressures, eventually succumbed in the late 5th century following a series of devastating invasions of imperial territory by Germanic barbarian tribes. Romulus Augustulus is widely considered the last emperor of the West, his reign ending with a forced abdication in 476 AD. However, Julius Nepos maintained a claim to the title, a claim that was recognized by the Eastern Empire, until his death in 480 AD. Following Nepos's demise, the Eastern emperor Zeno took a decisive step, abolishing the administrative division of the position and boldly proclaiming himself as the sole emperor of a notionally reunited Roman Empire.

The Eastern Roman Empire: A Millennium of Endurance

The subsequent Eastern emperors, ruling from the magnificent city of Constantinople, continued to proudly style themselves "Emperor of the Romans," a title later expressed in Greek as basileus Ῥωμαίων. However, to distinguish their distinct cultural and historical trajectory, modern scholarship often refers to them as "Byzantine emperors." The lineage of Roman emperors in Constantinople finally came to a poignant end with Constantine XI Palaiologos, who valiantly died defending his city during its tragic Fall to the Ottoman Empire in 1453.

Imperial Authority: Divine Claims and Contested Succession

Evolving Imperial Titles and Divine Mandate

Beginning with Heraclius in 629 AD, the "Byzantine" emperors formally adopted the monarchic title of basileus (βασιλεύς). This title became exclusively reserved for the Roman emperor and the ruler of the rival Sasanian Empire, while other rulers were henceforth referred to by the lesser designation of rēgas. Beyond their earthly authority, some emperors were even accorded divine status after their death, reflecting the pagan traditions of Rome. With the eventual hegemony of Christianity across the empire, the emperor's role transformed; he came to be seen not just as a secular ruler, but as God's chosen representative on Earth, a special protector and leader of the Christian Church, though in practice, an emperor's authority on Church matters was frequently subject to challenge and debate.

Rival Claims and the "Problem of Two Emperors"

Due to the profound cultural rupture caused by the Turkish conquest of Constantinople, most Western historians typically regard Constantine XI as the last genuinely meaningful claimant to the title of Roman emperor. Nevertheless, from 1453 onward, one of the significant titles adopted by the Ottoman Sultans was "Caesar of Rome" (Turkish: Kayser-i Rum), a claim they maintained as part of their imperial titles until the Ottoman Empire's dissolution in 1922. Furthermore, a Byzantine group of claimant Roman emperors existed within the distant Empire of Trebizond until its conquest by the Ottomans in 1461, although they had used a modified title since 1282. For centuries, the Eastern emperors in Constantinople had been universally recognized and accepted as the legitimate Roman emperors, not only within the East which they governed but also by the papacy and the Germanic kingdoms of the West. This acceptance, however, fractured following the deposition of Constantine VI and the unprecedented accession of Irene of Athens as Empress regnant in 797 AD. Objecting both to a woman ruling the Roman Empire in her own right and to issues with the eastern clergy, the Papacy then controversially created a rival lineage of Roman emperors in Western Europe: the Holy Roman Emperors. These emperors presided over the Holy Roman Empire for the majority of the period between 800 and 1806, their coronations famously giving rise to the medieval dilemma known as the "problem of two emperors," as they were never recognized as legitimate Roman emperors by the imperial court in Constantinople.

Case Study: Marcus Opellius Macrinus – An Emperor from Beyond the Senate

A Glimpse into Imperial Succession and Downfall

Marcus Opellius Macrinus (c. 165 – June 218 AD) served as Roman emperor from April 217 to June 218 AD, reigning jointly with his young son Diadumenianus. His reign marked a significant departure from tradition, as Macrinus was a member of the equestrian class, making him the first emperor who did not hail from the more prestigious senatorial class. Adding to his unique status, he was also the first emperor who never had the opportunity to visit Rome during his tenure. Prior to his unexpected ascent to the imperial throne, Macrinus had served under Emperor Caracalla as a praetorian prefect, a crucial role that involved managing Rome's civil affairs. However, in a desperate bid to protect his own life, he eventually conspired against Caracalla and orchestrated his assassination, subsequently succeeding him as emperor.

Challenges and a Tragic End

Macrinus was proclaimed emperor of Rome by April 11, 217, while he was situated in the eastern provinces of the empire, and his claim was swiftly confirmed by the Senate. Despite this, he never managed to return to Rome throughout his entire reign. His predecessor, Caracalla, had left Rome's coffers severely depleted and the empire embroiled in costly wars with several formidable kingdoms, including Parthia, Armenia, and Dacia. As emperor, Macrinus initially attempted to enact vital reforms aimed at restoring both economic and diplomatic stability to Rome. While his diplomatic efforts successfully secured peace with each of the individual kingdoms, the substantial monetary costs associated with these treaties and the subsequent fiscal reforms generated significant unrest within the Roman military. Caracalla's influential aunt, Julia Maesa, shrewdly capitalized on this widespread military discontent, instigating a rebellion to have her fourteen-year-old grandson, Elagabalus, recognized as emperor. Macrinus was ultimately overthrown at the decisive Battle of Antioch on June 8, 218, and Elagabalus promptly proclaimed himself emperor with the crucial backing of the rebellious Roman legions. Macrinus attempted to flee the battlefield, hoping to reach Rome, but he was captured in Chalcedon and later executed in Cappadocia. He had sent his son, Diadumenianus, to the care of Artabanus IV of Parthia, but the young prince was also captured before reaching his destination and met the same tragic fate. Following Macrinus's death, the Senate, in a punitive act known as damnatio memoriae, declared both him and his son enemies of Rome, ensuring their names were struck from all records and their images destroyed, effectively attempting to erase their memory from history.

Frequently Asked Questions About Roman Emperors

What was the primary title of a Roman Emperor?
The most significant and defining title for a Roman emperor was Augustus, granted to Octavian in 27 BC, which marked the beginning of the imperial period. Over time, in the East, this evolved into Basileus.
How did Roman emperors achieve legitimacy?
An emperor's legitimacy depended on two key factors: control of the army, which often led to a proclamation by his troops, and formal recognition by the Senate, which would invest him with imperial titles. Often, both elements were crucial.
Why did Romans distinguish emperors from kings?
The Romans harbored a historical aversion to kingship, stemming from the tyrannical rule of early Roman kings. Early emperors like Augustus carefully presented themselves as "first citizens" (princeps civitatis) and leaders of the Republic, rather than absolute monarchs, to avoid this negative association.
When did the Western Roman Empire fall?
The Western Roman Empire is generally considered to have collapsed in the late 5th century, with the traditional date often cited as 476 AD, following the forced abdication of Romulus Augustulus.
Who was the last Roman emperor?
This depends on whether you refer to the West or East. In the West, Romulus Augustulus (476 AD) is often considered the last, though Julius Nepos held a recognized claim until 480 AD. In the East, and generally recognized as the ultimate last Roman emperor, was Constantine XI Palaiologos, who died during the Fall of Constantinople to the Ottoman Empire in 1453.
What was the "problem of two emperors?"
The "problem of two emperors" arose in medieval Europe when the Papacy, objecting to the rule of Empress Irene in Constantinople, crowned Charlemagne as "Roman Emperor" in 800 AD. This created a rival line of Western emperors (the Holy Roman Emperors) who were never recognized as legitimate Roman emperors by the court in Constantinople, leading to a period of contested imperial claims.
Who was Macrinus, and why was his reign significant?
Marcus Opellius Macrinus was Roman emperor from 217 to 218 AD. His reign was significant because he was the first emperor from the equestrian class (not senatorial) and the first never to visit Rome during his rule. He rose to power by assassinating his predecessor, Caracalla, and attempted reforms but ultimately faced military unrest and was overthrown.