Succession Crisis: The Roman Empire’s Hidden Weakness

Historians typically date the foundation of the Roman Empire to 27 BCE, when the Senate granted Augustus the title of “princeps“. Augustus had been the most powerful figure in the moribund Republic for several years now, since his destruction of Mark Anthony’s forces at the Battle of Actium, but this action formalized the transition from oligarchic republic to monarchy. Sort of. The title “princeps” merely means “first” or “foremost”, or perhaps “first among equals”. Its ambiguity suited a new regime that was deliberately attempting to obscure the nature of its power.

Rome was a nation that took great pride in its republican government. The fall of the original Roman Kingdom was a much-celebrated foundational myth, and much of the support for the assassination of Julius Caesar was due to the persistent rumors that he was planning to have himself crowned king. By the 20s BCE, the long cycle of civil wars and proscriptions had considerably increased the support of the populace for a dictator who could bring about stability, but the old families and oligarchic clans still bitterly resented the idea of submission to a monarch. Augustus chose to address this problem by finessing it. Rather than attempting to establish a formal monarchy, he simply accumulated so much power within the existing republican constitutional system that it was impossible for anyone to gainsay him. The Senate, the assemblies, the tribunes, the consuls—all these institutions continued to function normally. They simply now lived in Augustus’s shadow. But while this system worked well in his lifetime, and for decades to come, it had a fundamental flaw. Official or not, Augustus had still created a monarchy. And he’d created one without any accepted methods of succession. This would become a problem

It’s worth unpacking exactly how this functioned. We talk about Augustus as being “Emperor of Rome”, but no such title existed at the time. The modern word “emperor” comes from the Latin word “Imperator“, which originally meant simply “commander”. Augustus took this as one of his names, but it was not a formal title or position. Augustus’s true power rested on his control of the legions and the support of the public. In practice, his Empire was a military dictatorship. It was formalized, however, by a number of senatorial grants of power. We already mentioned the title of “princeps“, which gave its name to the early phase of the Roman Empre: the Principate. Additionally, he was granted proconsular imperium, which is to say the same right of command over the Roman state as one of the elected Consuls, direct control over many of the Empire’s provinces, and the powers of the tribune and the censor. Together, these formed a bundle of power sufficient to dominate the state. But while the Senate had granted them to Augustus, there was never any formal transition to a monarchy. The powers never became inherent rights of a specific office, entitlements of a family or Crown. Instead they were magistracies, offices of the Republic which had been bestowed upon a specific individual. This polite fiction worked well at first, but began to wear thin almost immediately.

This was the central paradox of the Imperial Roman system. All power rested in the position of the emperor, yet it could be almost impossible to determine who the legitimate emperor was. The question of the succession, which is of utmost importance to any monarchical system, had no legal framework to back it beyond tradition or brute force. Knowing this, it is perhaps inevitable that the entire institution of the succession would eventually collapse, and with it, take the rest of the Empire.  

During the first and second centuries of the Roman Empire, succession was usually handled in the manner most common amongst empires and autocracies—by inheritance. Rome was unusual in that it was not unheard of for the heir to adopted, rather than the emperor’s biological son, but the basic principle remained that of hereditary succession. However, unlike medieval European monarchies, Roman succession was essentially totally at the discretion of the emperor. Most monarchies are set up to limit the succession as tightly as possible. The principle of primogeniture, for example, compels the ruler to select his eldest male heir, no matter what his preferences. Other noble houses or kingdoms may have had a broader pool of potential heirs, but in general the goal was to limit the number of people who could rightfully claim the throne and to make it clear and obvious who the next monarch is. In many ways, the Roman system was highly advantageous. If lacking a proper biological heir, Roman emperors often simply chose one of their chief lieutenants or supporters as the next emperor, allowing men of talent to rise to the top. But what this custom provided in flexibility, it took away in stability. It may seem ridiculous that something like Salic Law was a major issue in European politics as late as the 19th century, but the purpose of this esoteric codes and laws was to attempt to ensure that the ruler always had legitimacy.

This is one of the core requirements of any government. In the United States, we know that a President is legitimate because they were awarded a majority of electoral votes after elections are certified by the states and the votes are counted by Congress, after which the winner officially gains their powers of office when they are inaugurated. In the United Kingdom, the leader of whatever political party wins a majority of seats in Parliament is asked by the Queen to form a new government. The details don’t really matter, the important thing is that there is a universally-recognized process, a legitimating institution, that can determine the new ruler. Rome never really developed one of these.

Because no singular position of “emperor” existed, no formal apparatus for succession could be created. Augustus had been granted his powers by the Senate, which implied that they had the power to strip them away as well. And in fact, while Augustus named his stepson Tiberius as his heir in his will, he was also then vested with all of Augustus’s various powers by the Senate in a separate ceremony in 14 CE. Now, there are two possibilities that present themselves here, both of which would have been conductive to stability. The first is that the Senate was a totally powerless body, rubber-stamping the decisions of the emperor. It existed merely as a façade, a remnant of the Republic used to mask the absolute power of the emperor. This would eventually become increasingly true as Roman rule came to depend more and more on raw military might, but during the first and second centuries CE, the Senate remained a major factor in Roman politics. The second possibility would be a clear division of powers between the Emperor and the Senate, with the emperor having the right to nominate his successor, but also needing senatorial approval for him to take the throne. In some ways, this would have been an ideal balance. Rome would have a clear and simple path for legitimization of the succession, but it would retain the flexibility of the emperor’s prerogative. Unfortunately, the Roman political system was not that sophisticated. Instead of a single legitimating mechanism, the two ways of determining succession (inheritance and senatorial approval) existed side by side, neither one ever really acknowledging the other. In fact, Roman political tradition didn’t even really acknowledge the existence of the Empire. It’s not uncommon to find Roman writers in the Second Century CE still talking about “the Republic”. Imperium continued to legally derive from the Senate, but emperors passed it down to heirs as they would their villas and slaves, a co-mingling of private and public functions that was never really addressed. This would later have disastrous consequences, as Senate and Emperor increasingly found themselves in conflict.

As early as the Era of the Five Good Emperors—usually considered the zenith of Imperial Rome—these contractions can be seen. Trajan had been formally adopted by Nerva as heir before the former’s death, but Trajan still felt the need to begin his rule in 98 CE with a tour of the various major army commands to secure their support before traveling to Rome to bargain with the Senate for his support. His heir, Hadrian, was adopted on Trajan’s deathbed in 117 CE, and wrote to the Senate to unilaterally declare himself emperor based on the support of the military. Most of the Senate supported him, but several opposing senators were executed. Both were strong, universally-recognized rulers who presided over an era of stability and security for the Empire, and yet both of their transitions to power were essentially negotiations to gain the support of major power blocs. The system worked—but only as long as one man was able to rapidly secure a consensus. When this didn’t occur, it was a recipe for anarchy. In 193 CE, the Emperor Pertinax was assassinated by the Praetorian Guard, who then quite literally sold the position to Didius Julianus for the price of 25,000 sesterces per soldier. He was then able to convince the Senate to support him. A number of prominent generals rose up to oppose him, most prominently Septimius Severus. Severus based his claim to the throne on acclamation by the army, which was the unacknowledged foundation that Augustus had built his regime upon, while Julianus claimed the formal support the Senate. Though the war ended precipitously when Julianus was also assassinated by the Praetorian Guard, a precedent had been set. The legitimacy of the principate had become a matter open to debate, and usually a debate of swords.

Augustus: First Emperor of Rome

In 235 A.D, Emperor Alexander was murdered by his own troops at the behest of a usurper named Maximinus Thrax. This would spark the Third Century Crisis, a fifty year period marked by almost constant civil war that would see twenty-six emperors come and go. There had been coups and usurpations before, but what made the Third Century Crisis unique was the length of time it lasted, and the complete collapse of any vestige of legitimate authority. To use Severus as an example once more, after seizing power through the military be paid bribes to the Senate to gain their support and worked to establish a dynasty. Within a generation or two, the exact nature of how they had come to rule was unimportant. But during the Third Century Crisis, all of the trappings of legitimacy were stripped away. More and more emperors were common soldiers (so-called “barracks emperors”) who were able to seize a chance, not high-born officials chosen by the Senate or previous emperor. And there was no attempt to mask the fact that their rule was guaranteed first and last by force of arms. With previous military coups, they had been isolated incidents, and the new emperor worked to envelop himself in the traditions and customs that provided legitimacy. But with emperors being killed approximately once every two years, there was no time for this process to take place. Instead, over the course of the fifty year Crisis, coup d’état became the new and accepted norm for establishing leadership. For two generations of Romans, that was the only method they knew.    

Eventually, the emperors Aurelian and Diocletian brought an end to the Crisis, but the damage had been done. Never again in Roman history would anyone believe that imperial power relied on anything more sophisticated than military might. Powerful and effective rulers such as Valentinian I or Constantine the Great would still arise occasionally, but the underlying stability of the empire had been fatally damaged. No matter how powerful an individual ruler is, once naked force has become the underpinnings of his regime it is doomed. The purpose of legitimacy is to determine who the true ruler is. But when force is your legitimating mechanism, power simply then goes “to the strongest”. Ironically, it was the escalating cycle of civil wars that tore apart the Republic and paved the way for Augustus to establish the Empire to begin with. Now, history repeated, as the Empire began to fracture. When every successful general knew he had a shot at the throne, long-term stability became impossible. Civil wars had once been brief affairs puncturing the transition from dynasty to dynasty, now they became the normal method of succession. Even the efforts to address this were damaging. After the Third Century Crisis, the size of the individual legions was greatly reduced in an effort to lessen the power of each commander. But with pressure on the frontier from the Germans and Huns ever-increasing, this couldn’t help but set up a vicious cycle. A strong military was needed to protect the Empire, but it was also the Empire’s single greatest threat.

Among the later emperors, Diocletian seemed to understand this best. His reign marks the traditional end of the Principate and the beginning of what historians call the Dominate, as emperors increasingly eschewed the republican pretensions of the Augustinian system. Earlier emperors had titled themselves “Princeps“, first among equals. Now, a new title came into vogue: Dominus. Translatable to “lord” or “master”, it was the traditional title used by slaves to address their owners. Augustus had made a point of forbidding people from referring to him by it. Diocletian adopted it as one of his official titles. With the traditional Roman elite devastated by a half-century of civil war, Diocletian attempted to reconstruct the government along traditional monarchical lines.

Key to this was his creation of the Tetrarchy, which can be seen as a last-ditch attempt to rebuild the succession along a simple, sustainable lines. Appointing co-emperors and junior emperors had always been common in Rome, but usually it was an attempt to either placate a rival, or a way to cement your heir’s position by giving him a measure of power. What Diocletian did is attempt to standardize this practice. He, the emperor, appointed a co-emperor. They would each bear the title ‘Augustus’. Then each Augustus appointed a junior emperor, or ‘Caesar’. When an Augustus died, the Caesar would ascend to the position of Augustus and then appoint a Caesars of their own. In theory, this would accomplish two goals. One, put the choice of the succession directly back into the hands of the emperor. Two, establish a clear process of legitimization. Someone is emperor because he was chosen as Caesar by the previous emperor, who in turn was chosen by the emperor before him. Diocletian attempted to solidify this by doing the unprecedented: voluntarily abdicating the throne in 305 CE in order to try and manage the succession personally. Unfortunately, the system did not survive long. Though Diocletian was able to retire to Croatia and spend the rest of his life growing cabbages, a new round of civil wars broke out almost immediately, and when Constantine eventually rose to power, he did it by brute military force.

In theory, the Tetrarchy should have provided a solution to Rome’s woes. But legitimacy cannot be conferred by declaring it so. What legitimacy needs most of all is time. Time to be accepted, and time to become the new norm. With Rome already so deep in its cycle of political violence, it was highly unlikely that Diocletian’s dream could have lasted long enough to cement its place in Roman society.

Obviously, it would be far too reductive to place the entire blame for the Fall of Rome upon a single flaw in the constitution. The downfall of the Roman Empire was a process that lasted centuries, and dozens of factors contributed, including barbarian invasions, internal political infighting, territorial over-extension, the lack of a strong administrative state, economic weakness, etc. I’m probably leaving out at least a dozen. But the lack of any coherent succession mechanism was a constant problem for the Empire, ensuring that any dispute had the potential to spiral out of control. It exacerbated conflicts, giving any ambitious soldier the ability to dream of rising to the top, and forced existing sovereigns to spend a disproportionate amount of their political capitol securing their rule. It was a fatal flaw built into the imperial system from the start. It’s ironic. Augustus’s decision to create a non-formalized, “republican” form of monarchy was a brilliant political move that stabilized his reign and saved the Republic from total collapse. An effort to have himself declared King or establish direct, personal rule would have sparked immense backlash. But that same decision would haunt his successors for centuries to come.

Full Disclosure: This post was adapted from an essay entitled “The Paradox of Imperial Rome”, written in October 2013 for a history class at Brandeis University.

The Roman Empire in 125 CE

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