Interregnum is a word that refers to the period when the state has no leader – the previous leader has died or lost an election and the new leader has not taken office. In Roman law, interregnum was accompanied by the proclamation of justitium (a state of emergency) which was designed to deal with adverse public reaction upon hearing of the death of the sovereign.
I’m going to use interregnum in a different way -- to describe the Empire between 280 to 378 A.D. That period began with the reign of Diocletian, passed through Constantine, and ended with Valens. I’m calling it an interregnum because it was an interruption in the fall of the empire – made possible by strong leadership and a new form of governance.
Diocletian became emperor by a stroke of luck. He was losing a battle with the emperor Carinus, when several of Carinus’ officers, offended with his seducing of their wives, took revenge and killed him. Immediately they recognized Diocletian as their true emperor.
He was a strong leader who deserves first rank in the history of the empire, but also suffers from a bad reputation fostered by Christian writers who curse him for his persecution of their people.
Here’s what Gibbon had to say:
His abilities were useful rather than splendid; a vigorous mind, improved by the experience and study of mankind; dexterity and application in business; a judicious mixture of liberality and economy, of mildness and rigor; profound dissimulation, under the disguise of military frankness; steadiness to pursue his ends; flexibility to vary his means; and, above all, the great art of submitting his own passions, as well as those of others, to the interest of his ambition, and of coloring his ambition with the most specious pretences of justice and public utility. Like Augustus, Diocletian may be considered as the founder of a new empire. Like the adopted son of Caesar, he was distinguished as a statesman rather than as a warrior; nor did either of those princes employ force, whenever their purpose could be effected by policy.
Soon after taking power, Diocletian named a colleague, Maximian, Caesar and assigned him control of the western provinces. This act gave him free reign to deal with problems along the Danube – five years worth. The dual-emperor model worked well but did nothing to solve the problem of succession. Diocletian fixed that problem in 293 A.D.by having Maximian and himself name their replacements – Julius Constantius and Galerius Maximianus.
All four of them had been participating in the wars starting in 286 A.D: a Berber revolt in Africa, a Persian seizure of Armenia, a pretender in Egypt declaring himself emperor, and a breakaway commander in Britain. These challenges took four years to clean up. The Goths and Germans were also troublesome during this time, but they were held back by a superior Roman effort and dedicated commanders. The Germans spent much of the time fighting among themselves.
Rome, the city, was now isolated and unimportant. Diocletian visited there only once because it was just too far from the action. The tetrarchs chose Trier, Milan, Thessalonica, and Nicomedia for their capitals.
By 304, Diocletian was old and sick. He decided to resign and convinced his partner to do likewise. The dual resignation date was May 1, 305. The two new emperors ascended to the throne and named their replacements as before, but the wrong people were passed over in the process. Severus and Maximinus were selected, but the sons of Constantius and Maximian – Constantine and Maxentius – were passed over. When Constantius died prematurely in 306, his army proclaimed Constantine as new emperor in the west. Before Galerius could elevate Severus in opposition, Maxentius proclaimed himself emperor in Rome. Ultimately, Constantine and Maxentius faced off in a battle at Milvian Bridge on October 28th, 312 with Constantine the winner. Maxentius drowned trying to cross the Tiber.
Now Constantine was in control of the western empire and Licinius was in control of the east. The latter had come to power in 308 A.D. as the nominee of Galerius to replace Severus in the west. But he was never able to defeat Maxentius so he had to be content to stay in the Balkans and control the eastern provinces. The uneasy partnership between Constantine and Licinius lasted for twelve years. Uneasy because Constantine’s temperament would not allow any compromise in his vision for Rome. That vision had two major components: making Christianity part of Roman life and becoming sole emperor.
Gibbon tells us of the man:
“The person, as well as the mind, of Constantine, had been enriched by nature with her choices endowments. His stature was lofty, his countenance majestic, his deportment graceful; his strength and activity were displayed in every manly exercise, and from his earliest youth, to a very advanced season of life, he preserved the vigor of his constitution by a strict adherence to the domestic virtues of chastity and temperance. He delighted in the social intercourse of familiar conversation; and though he might sometimes indulge his disposition to raillery with less reserve than was required by the severe dignity of his station, the courtesy and liberality of his manners gained the hearts of all who approached him. The sincerity of his friendship has been suspected; yet he showed, on some occasions, that he was not incapable of a warm and lasting attachment. The disadvantage of an illiterate education had not prevented him from forming a just estimate of the value of learning; and the arts and sciences derived some encouragement from the munificent protection of Constantine. In the dispatch of business, his diligence was indefatigable; and the active powers of his mind were almost continually exercised in reading, writing, or meditating, in giving audiences to ambassadors, and in examining the complaints of his subjects. Even those who censured the propriety of his measures were compelled to acknowledge, that he possessed magnanimity to conceive, and patience to execute, the most arduous designs, without being checked either by the prejudices of education, or by the clamors of the multitude.
In the field, he infused his own intrepid spirit into the troops, whom he conducted with the talents of a consummate general; and to his abilities, rather than to his fortune, we may ascribe the signal victories which he obtained over the foreign and domestic foes of the republic. He loved glory as the reward, perhaps as the motive, of his labors. The boundless ambition, which, from the moment of his accepting the purple at York, appears as the ruling passion of his soul, may be justified by the dangers of his own situation, by the character of his rivals, by the consciousness of superior merit, and by the prospect that his success would enable him to restore peace and order to the distracted empire. In his civil wars against Maxentius and Licinius, he had engaged on his side the inclinations of the people, who compared the undissembled vices of those tyrants with the spirit of wisdom and justice which seemed to direct the general tenor of the administration of Constantine.”
After a winning a battle against Licinius in 317 A.D. Constantine won concessions including most of the Balkans and the guarantee that his sons would be in line for the throne. Then, in a final showdown 324 A.D, Constantine defeated his rival at Hadrianopolis.
The emperor now turned his attention to the construction of a new capital at Byzantium (Constantinople) which took six years. Then, in the 330s A.D, he was engaged with the Germans along the Danube, defeating the Goths in 332 A.D. and the Sarmatians in 334. These victories brought back to Rome much of the Dacian territory originally won by Trajan.
Constantine died in 337 A.D. after being baptized as a Christian. His reign had marked two enormous changes in the empire: the embracing of Christianity and the move of the capital to Constantinople.
Before his death, Constantine devised a plan to divide the empire between his four sons, an attempt to re-create the tetrarchy he had dismantled years before. But the plan did not take root because the sons became rivals instead of partners. Constantine II was killed in battle in 340 A.D and Constans was over thrown and killed in 350 A.D. The remaining son, Constantius II, named an associate Julian in 360 A.D, who turned on his mentor and killed him in 361 A.D. Julian died suspiciously in 363 while fighting the Persians and his replacement Jovian died the next year when he was poisoned by carbon monoxide from a fire in his tent.
The death of Constantine left Rome with no heir to the throne, so the army chose a Pannonian officer of humble origin, Valentinian, to replace him. He assumed power as Valentinian I in the west and named his brother Valens to control the Balkans and points to the east. Valentinian spent his entire reign fighting the Germans: the Alemanni during the 360s A.D. and then the Quadi and Sarmatians in the 370s. He died of a stroke in 375 A.D.
Valens angered the Goths by mismanaging Rome’s relationship with them. That and the pressure they felt from the Huns on their eastern flank mobilized the Goths against Rome. They inflicted a crushing defeat on Valens at Hadrianopolis in 378 A.D, signaling the end of my interregnum. There would be no more pauses before the empire crumbled to dust.
This story shows how two great leaders were able to propel the Empire forward by strength of their will. Those who succeeded them were pale in comparison. The Goths saw this and knew the time had come to strike.