15.3 Political instability and the rise of soldier emperors

The Crisis of the Third Century saw Rome's political landscape crumble. Between 235 and 284 CE, the empire cycled through over 20 emperors, most of them military men who seized power by force rather than through traditional political channels. Understanding this period explains how Rome went from a relatively stable principate to a fragmented empire that needed radical restructuring under Diocletian.

The turmoil went well beyond palace coups. Invasions along every frontier, a collapsing currency, and breakaway regional empires all threatened to tear Rome apart for good. Brief recoveries under emperors like Aurelian showed the empire still had resilience, but lasting stability wouldn't return until Diocletian's reforms created an entirely new system of governance.

Soldier Emperors and Instability

Year of the Six Emperors and Barracks Emperors

The Year of the Six Emperors (238 CE) is one of the clearest snapshots of how unstable Rome had become. Six different individuals claimed the title of emperor within a single year, each backed by different factions of the military or Senate. The episode showed that imperial power now depended almost entirely on who controlled the legions.

The term barracks emperors refers to military commanders who were proclaimed emperor by their troops or who seized power through force. These men:

• Often had little experience in political administration or civilian governance
• Prioritized keeping the army loyal (through pay raises, donatives, and campaigns) over broader imperial needs
• Rose and fell quickly, since the same soldiers who elevated them could just as easily turn on them
• Notable examples include Maximinus Thrax, Philip the Arab, and Decius

Maximinus Thrax and the Gordian Dynasty

Maximinus Thrax (r. 235–238 CE) is generally considered the first true soldier emperor. He came from humble origins on the frontier and rose entirely through the military ranks. He seized power after the assassination of the last Severan emperor, Alexander Severus, and his reign set the pattern for what followed: heavy military campaigning funded by aggressive taxation that alienated the Senate and civilian population.

The Gordian dynasty briefly interrupted the rule of soldier emperors, though it ended badly:

• Gordian I and II (r. 238 CE) were proclaimed emperors by the Senate in direct opposition to Maximinus Thrax. Gordian I was an elderly senator; his son Gordian II co-ruled with him. Both died within weeks when forces loyal to Maximinus defeated them in North Africa.
• Gordian III (r. 238–244 CE), grandson of Gordian I, became emperor as a teenager. He ruled under the guidance of the Senate and his praetorian prefect Timesitheus, but after Timesitheus died, Gordian III lost his most capable advisor and was soon killed during a campaign against the Sassanid Empire.

Philip the Arab

Philip the Arab (r. 244–249 CE) succeeded Gordian III after likely playing a role in his downfall. Originally from the Roman province of Arabia, Philip rose through the military ranks and became praetorian prefect before claiming the throne.

Key events of his reign:

• Negotiated a peace treaty with the Sassanid Empire to secure the eastern frontier, freeing him to deal with problems elsewhere
• Celebrated the 1,000th anniversary of Rome's founding in 248 CE with elaborate games and festivities, a major propaganda event meant to project stability
• Lost power when the general Decius, sent to suppress a Danubian revolt, was proclaimed emperor by his own troops. Philip was defeated and killed in battle in 249 CE.

Emperors During the Crisis

Decius and Religious Persecution

Decius (r. 249–251 CE) came to power as a prominent general and tried to restore what he saw as traditional Roman values. His most significant domestic policy was the first empire-wide persecution of Christians.

The persecution worked through a system of enforced compliance:

1. All citizens were required to perform a sacrifice to the traditional Roman gods in front of witnesses.
2. Those who complied received a certificate (called a libellus) proving they had sacrificed.
3. Anyone who refused faced imprisonment, torture, or execution.

The goal was religious uniformity as a way to restore divine favor and imperial unity. Decius didn't single out Christians by name in his edict, but Christians were the largest group who refused to sacrifice, making them the primary targets.

Decius died fighting the Goths at the Battle of Abritus in 251 CE, becoming the first Roman emperor killed in battle by a foreign enemy.

Valerian and Gallienus: Joint Rule and Capture

Valerian (r. 253–260 CE) and his son Gallienus (r. 253–268 CE) tried a practical solution to the empire's problems: they split responsibilities, with Valerian handling the east and Gallienus the west.

It ended in disaster for Valerian. In 260 CE, the Sassanid king Shapur I captured him in battle, making Valerian the only Roman emperor ever taken prisoner by a foreign power. He was subjected to public humiliation and died in captivity. Sassanid rock reliefs at Naqsh-e Rostam still depict Shapur triumphing over the kneeling Roman emperor.

Gallienus, now ruling alone, faced an empire fracturing in real time:

• The Gallic Empire (encompassing Gaul, Britain, and parts of Hispania) broke away under Postumus in 260 CE
• The Palmyrene Empire under Odaenathus (and later his wife Zenobia) took control of Rome's eastern provinces
• Numerous usurpers challenged Gallienus across the remaining territory

Despite this chaos, Gallienus made lasting military reforms:

• Created a mobile cavalry force (the comitatus) that could respond quickly to threats anywhere, rather than relying solely on legions stationed at fixed borders
• Appointed professional military officers called duces to command regional armies, reducing the Senate's traditional role in military leadership

These reforms outlasted Gallienus himself and influenced the later restructuring of the Roman military.

Aurelian: Restorer of the World

Aurelian (r. 270–275 CE) earned the title Restitutor Orbis ("Restorer of the World") because he actually managed to put the fractured empire back together. He came to power after the brief reign of Claudius Gothicus and moved quickly on multiple fronts.

His major accomplishments:

• Defeated the Palmyrene Empire in the east, capturing Queen Zenobia and bringing her to Rome, where she was paraded in his triumphal procession
• Reconquered the Gallic Empire in the west, reuniting all Roman territory under a single emperor for the first time in over a decade
• Built the Aurelian Walls around Rome, a massive defensive circuit that acknowledged a new reality: the capital itself was no longer safe from barbarian raids. Much of this wall still stands today.
• Promoted the cult of Sol Invictus (the Unconquered Sun) as a unifying state religion, attempting to create religious cohesion across the diverse empire

Aurelian was assassinated by his own officers in 275 CE, reportedly due to a conspiracy sparked by a forged document. His death plunged the empire back into instability, demonstrating how dependent recovery was on individual leaders rather than stable institutions.

Defining the Era

The Crisis of the Third Century

The Crisis of the Third Century (235–284 CE) was a near-death experience for the Roman Empire. Its defining features all reinforced each other in a destructive cycle:

• Political chaos: Over 20 emperors in roughly 50 years, most dying violently. No reliable mechanism existed for peaceful succession.
• Military pressure: Goths, Franks, Alamanni, and other groups raided across the Rhine and Danube frontiers, while the Sassanid Empire pressed hard from the east.
• Economic collapse: Emperors debased the silver currency to pay their armies, which triggered severe inflation. Trade networks broke down as security deteriorated.
• Fragmentation: The Gallic Empire and Palmyrene Empire governed large portions of Roman territory independently, showing that the centralized imperial system had failed to protect its provinces.

Aurelian's reunification addressed the most visible symptom (territorial breakup), but the deeper structural problems persisted. It took Diocletian (r. 284–305 CE) and his sweeping administrative, military, and economic reforms to stabilize the empire on a new foundation, ending the crisis and ushering in the period historians call the Dominate.