Constantinian Dynasty
Calm Before the Storm
In response to the tumult that befell the Roman Empire in the Crisis of the Third Century, the Emperor Diocletian abolished the Principate system that outwardly adhered to certain vestiges of the old Republican constitution in favor of the Dominate, which was supposed to bring the Roman Empire down to a more manageable size and to also ensure against future succession crises. To this end, Diocletian split the Roman Empire into Western and Eastern portions with an Augustus ruling in each half and then further subdivided the halves into two administrative districts with a Caesar in each half reporting to the Augustus while simultaneously being directly responsible for one-quarter of the Empire. When an Augustus died or left office, then, his Caesar would succeed him and in turn appoint a new Caesar, and everything would be great and there would be no more icky, nasty civil wars. In theory, anyway.
Diocletian set this system up in 284/285 and ruled in the East with a man named Galerius directly under him while his co-Emperor in the West was a man named Maximian whose Caesar was Flavius Valerius Constantius. In order to solidify the whole arrangement, Constantius divorced his wife Helena and married Maximian's daughter Theodora, with whom he had at least six children (which makes writing about this family a huge pain in the ass). He also sent his son from his first marriage, Flavius Valerius Constantinus, to live with Galerius. Everything started out all right; Diocletian and Maximian were in power for 20 years, which was amazing, considering the reign of an Emperor during the preceding crisis was, on average, about 3 years (if not shorter). Satisfied that his system was going to work, Diocletian retired from office in 305 and forced Maximian to go with him. Galerius and Constantius succeeded them and all seemed to be going smoothly. Galerius named his nephew Maximinus Daia as his Caesar while Constantius chose a man named Severus as his (unrelated to the the Severan Dynasty from the last century). Everything went well...for about a year. Then it all came crashing down again.
Crisis of the Fourth Century
In the year 306, Constantius traveled to Britannia with his legions and his eldest son, Flavius. They were there to put down the Picts, which by that time had become an increasingly routine affair. Routine, of course, until the Western Roman Emperor suddenly dies. The sources are unclear about what killed Constantius, but he was not a very old man. Either way, upon hearing of Constantius' death, Galerius (now senior Augustus) confirmed Severus as the successor to Constantius. Some other people had different ideas, though. In Britannia, Constantius' soldiers proclaimed his son, now known as Constantine, Emperor. Galerius, fearful of the repercussions of this action, compromised with Constantine by legitimizing his position as Western Caesar under Severus. In Rome, hower, the Senate declared for Marcus Aurelius Valerius Maxentius, the son of the retired former Emperor Maximian (the latter of whom "confirmed" his son's ascension, despite the fact that he had no legal authority to do so). Maxentius' support was confined mainly to Italy while Constantine's power-base was, of course, was at this point in Britannia and Gaul. Galerius was all in a huff and commanded Severus to put down Maxentius' revolt. Severus was killed in 307 after being lured into a fake peace negotiation by Maxentius and his father. Constantine was now the rightful Augustus of the West. Trying to make a deal, Maximian gave Constantine his daughter Fausta in marriage for his support in the coming campaign against Galerius. Constantine declined, and in 308, Maximian went to Rome. What he hoped to accomplish there in relation to his son Maxentius is unknown, but he apparently hated retirement and wanted back into the action.
That same year, Maximian traveled to the East for a conference with his old friend Diocletian. Diocletian was evidently happy in retirement, not concerning himself with the chaotic succession crisis that had erupted in the West. Maximian evidently felt that the best way to get back into power was to do it with Diocletian by his side, both of them returning to the purple and going about like the good old days. Diocletian harshly rebuked his former colleague, saying in so many words that he didn't have time for Maximian's greed and ambition because he was too busy cultivating cabbages. Maximian returned to Gaul to be with Constantine and his daughter. However, following a Frankish invasion in 310, Maximian declared himself Emperor in opposition to Constantine. Constantine put down his father-in-law very quickly, but did not punish him for his crimes. Humiliated, Maximian tried to kill Constantine in his sleep. When that didn't work, Maximian either killed himself or was executed by Constantine.
In the East, Galerius died in mid 311. This was a blow to the system of tetrarchical rule because nobody else cared enough about it at this point to make it continue (except, of course, for Diocletian who was still alive at this point, but he's essentially irrelevant to the rest of the story). Upon Galerius' death, Daia and Valerius Licinianus Licinius divided the realm between themselves, ruling as co-equals. Licinius, however, made a deal with Constantine in opposition to Maxentius (whom Constantine intended to crush once and for all). Daia found out about this and as such, allied himself with Maxentius. In 312, Constantine invaded and took over most of northern Italy, making a beeline for Rome. Maxentius' forces seem to have outnumbered Constantine's, which might have led him to feel confident enough to engage him in open battle rather than adopting a defensive position inside the city. The battle that followed is known as the Battle ofthe Milvian Bridge, and it's one of the most famous battles in Late Antiquity. Before the battle, Constantine is said to have looked into the sky and had a vision of the labarum, which was the Greek letters Chi-Ro (as in CHRIST) juxtapositioned on top of one another (imagine a "P" in the middle of an "X"). Beneath it were the Greek words "Εν Τούτω, Νίκα" more famous to us as In Hoc Signo Vinces -- by this sign shall you conquer. Constantine allegedly had his soldiers paint the symbol onto their shields as they went into bloody combat against the usurper.
Bridge over Troubled Water
The Battle of the Milvian Bridge was significant and there can be no doubt as to its result: Constantine won and Maxentius died. But it's still controversial for a number of reasons, not the least of which is its importance to the legitimization of Christianity in the Empire. The iconographic story is that Constantine and his men were outnumbered and feeling demoralized. The vision Constantine has gives him and his army the strength to defeat the enemy and they all convert to Christianity, etc. Looking at the tactics of both commanders, however, some of this doesn't really add up. Maxentius' behavior before the battle was strange, given that he actually destroyed part of the bridge apparently in anticipation of a siege (which would have been a more sensible operation as that's the same way he managed to defeat Severus' army before killing him). However, he rebuilt the bridge and met Constantine's forces right there. Ancient sources are not clear as to how many troops Maxentius had, with some estimates giving him more and some estimates giving him less than Constantine. What is obvious, however, is that Maxentius was in trouble before the battle: Constantine had already defeated him twice shortly before, and Maxentius' support in Italy was quickly evaporating. What seems likely to me is that Maxentius had fewer men than Constantine and he wanted to use the bridge in the same way that the Spartans had used the narrow pass at Thermopylae eight centuries earlier: in the constricted space of the bridge, numerical differences wouldn't matter so long as Maxentius' men maintained formation and were fast enough to cut down Constantine's as soon as they appeared. And like Leonidas, Maxentius eventually had to give way to superior numbers, although in his case, there was no massive force coming to avenge him.
The Christian angle of the battle is disputed also. The labarum makes no appearance on the triumphal arch Constantine had built as a result of the battle and aside from a generic statement about having divine assistance, there's nothing distinctly Christian on there. Likewise, it's obvious that Constantine didn't go through a major religious conversion (that is, he wasn't "born again" in the sense that people are today) as a result of the battle because for years after, his coins still featured Sol Invictus -- the "Invincible Sun" god -- on them. The best I can think to say about it is that Constantine believed in a micro-syncretic version of Christianity, applying the imagery and outward appearances of Sol Invictus to Jesus, not really concerning himself that much with dogma until later on in his reign. After parading through Rome, Constantine apparently went directly to the Imperial palace without stopping to thank the state gods. Constantine thus adopted a type of Christianity, but it certainly had very little to do with loving one's enemy or friend or even son, as we will see.
Not-so-Civil War
To cement the prior alliance between Licinius and himself, Constantine gave the former his sister Constantia in marriage in 313. In that same year, the two Emperors jointly issued the Edict of Milan, which officially legalized the Christian religion. There is a misconception about that edict which says that it made Christianity the state religion; in fact, it did nothing of the sort because Licinius was a pagan as was just about everybody else in a position of authority. All it did was affirm legal tolerance for Christianity (which had been severely persecuted under the tetrarchy, particularly Diocletian, who still wasn't dead yet). At the same time, Daia attacked Licinius' territory and after a few brief skirmishes, was killed in Tarsus. Now with each man in control of half the Empire, both got a little too big for their britches and went to war against one another. They fought on and off for a few years until 320 when Licinius began a great persecution of Christians. By this time, Constantine had a more sophisticated understanding of and devotion to Christianity and Roman deities cease appearing on his coins. The two sides fought an epic battle at Chrysopolis in 324 with Constantine being the victor and ultimately the sole ruler of the Empire, thus bringing about the end of the Tetrarchy. Despite pardoning his brother-in-law, he later had Licinius killed.
Now that he was the only Emperor, Constantine began behaving in a highly autocratic manner. He now outlawed the upkeep of pagan temples and severely curtailed the rights of Jews in the Empire. He then had his son from his first marriage (and heir) Flavius Julius Crispus as well as his wife Fausta killed for unfounded allegations of treason (as they were supposedly having an affair). Constantine had by this time taken an interest in ecclesiastical matters. He gathered bishops from all across the Empire to Nicaea to lay down the ground rules for Orthodox Christianity. He moved the capital of the Empire to a run-down town in Greece called Byzantium, rebuilding it and renaming it Constantinople in honor of himself. It became a Christian city as he disallowed any pagan temples from being built within its boundaries. The relocating of the capital moved the center of power finally and decisively away from the West. The message Constantine was trying to get across was clear: one Empire, one Caesar, one God. Constantine took the proskynesis begun by Diocletian and added a new dimension to it: not only was it proper ettiquette to regard the Emperor with a religious reverence, it was mandatory. Constantine was the most powerful ruler on the planet and he had the direct support of the one true God.
Constantinople: the Original City of Brotherly Love
In 337, Constantine went the way of all flesh and died, but not before receiving a death bed baptism (which was very common among Christians in those days). Apparently not getting the picture that allowing multiple people to rule the Empire was not the best idea, he made his three sons his heirs: Constantius II, Constantine II, and Constans all got a share of the Empire. All of these men had been brought up as Christians rather than converting to the faith like their father. Constantius was the middle brother but was definitely the most important of the three. He took after his father in many ways, but excelled him in his autocracy and ruthlessness. In the months (possibly weeks) after his father's death, Constantius feared the possibility of another war of succession and therefore had his uncles and male cousins all killed except for the youngest ones, Constantius Gallus and Claudius Julianus. In the year 340, Constantine II got greedy and decided his youngest brother Constans didn't really need the territory that had been allocated to him after their father's death. Somewhat surprisingly, the army of the younger brother prevailed, and Constantine fell in the battle, giving Constans sole control of the West. Constans then banned pagan sacrifices in the territory under his control and attempted to reconcile Orthodoxy with Arianism.
In 350, a general named Magnentius rebelled against Constans. For some reason, Magnentius managed to get most of Constans' army to defect, although it's not immediately clear how or why. Either way, when Constans attempted to flee, he was killed. Furious, Constantius marched West to avenge his brother and put down the rebellion. Before leaving, he promoted his cousin, Gallus, to the rank of Caesar so he could take care of matters in the East while he was away. It took three long years before Constantius scored a decisive victory at the Battle of Mons Seleucus, after which Magnentius threw himself on his sword in despair. Gallus, meanwhile, was planning a campaign against the Persians, but needed a way to finance it. He took an idea innovated centuries earlier by the Emperor Tiberius but changed it up for modern times: when Tiberius wanted someone's money, he used to charge him with treason, find him guilty, execute him, and steal his estate; Gallus charged people with practicing witchcraft and took their money. Constantius worried that Gallus was preparing to make a move against him and therefore sent his men to Antioch, where Gallus was based, to figure out what was going on. They never returned to file a report. Constantius was now sure that his cousin was going to try to overthrow him, and thus called him to join him in the West to be officially made co-Augustus. Thrilled, Gallus went to meet his cousin, acting as if they appointment had already been confirmed. Unfortunately, as soon as he got there in 354, he was seized and arrested. Gallus was tortured and coerced into confessing that he was planning to usurp Constantius' position, but that it had been his deceased wife's (Constantius' sister) idea. Either way, Gallus was executed before the end of the year.
Constantius now had a problem. His brothers were dead and he had killed almost all of his male relatives. He had no sons and the only family member he had left was his cousin Claudius Julianus (whose father and brother he had killed). In 355, another revolt, this one led by Claudius Silvanus, broke out in Gaul. After successfully ending it that same year, the Persians made trouble for the Empire in the East. At the end of his rope, Constantius named Julianus his Caesar so he could go East. Julianus stayed in Gaul, fighting off the Germans. Julian (as he is usually called) was a surprisingly good commander, given that he had not received any military education as a youth. Indeed, his early years were mainly spent in Greece, from which he developed a strong sense of pro-Hellenism. When things got dicy for Constantius against the Persians, he ordered Julian to scale back his campaign in Gaul and send reinforcements. Julian's soldiers mutinied against this and proclaimed him Emperor (despite the fact that he had show no interest in usurping the throne). Hearing of this, Constantius went to move against his cousin, but grew ill on the way. Putting the interests of the Empire above a personal vendetta, he officially recognized Julian as his rightful successor before dying in 361.
Pagan Reformation
Julian was now the master of the Roman world. Upon reaching Constantinople, he was appalled at the state of his cousin's court; it was run by a huge retinue of eunuchs and freedmen and was overly inefficient and corrupt. Julian fired these people and put to death some others. There was one interesting thing about Julian that I haven't mentioned so far: unlike the rest of his family, Julian was a practicing pagan. He was raised a Christian, but converted away from his family's faith in Greece, which is why he is generally known as Julian the Apostate, a term derived from Christian sources of the era and the ones immediately following it. Julian disliked Christianity and instead practiced a form of Greek paganism, having been inducted into the Eleusinian Mysteries and being a firm Neoplatonist. He did not, however, engage in massive anti-Christian persecutions as might have been expected.
Compared to Diocletian or Valerian or Domitian, Julian was rather tame. He was of the opinion that one of the reasons that Christianity grew throughout the Empire was that people were so sympathetic to the martyrs and so impressed by their courage when facing death, that they themselves would go on to adopt it. His anti-Christian measures were therefore more institutional than personal. For example, he banned bishops from traveling at the state's expense, as they had done under Constantine I and Constantius II. He also forbade the teaching of Greek and Roman literature in Christian schools, suggesting that if the gospels were so important spiritually, they would be perfectly adequate on an educational level (which they were not, as their grammar and rhetoric were on the whole inferior to that of, say, the Iliad). At the same time, he lifted prohibitions on semi-heretical Christian sects that had been banned under his cousin in the hope that they would foment disunity among organized Christianity. Julian was angered when he realized that more and more people were converting to Christianity and felt that one reason was because of Christian charity. Therefore, he demanded that all pagan state temples should also engage in charitable acts to counteract the influence of the Christians.
In 363, Julian consulted the Sibylline books, which were Rome's oldest religious texts. He believed that they prophesied a successful campaign against the Persians, so he set out to ride against them. In actuality, he had great successes, getting as far as Ctesiphon, the capital of the Empire. When he realized that he would not be able to push any farther, Julian retreated to safer territory, but was mortally wounded in a small skirmish. He died a few days later in his camp. Later (Christian) writers have claimed that his last words were "you have won, Galilean," but that's obviously quite unlikely.
Conclusion
After Julian, there would be no more Emperors from the Constantinian Dynasty. Shortly after his death, the general Jovian was declared as his successor. After only eight months in power, Jovian evidently choked to death on the fumes from the freshly painted walls in his room while he was asleep. Jovian was succeeded by two brothers, Valentinian I and Valens who in 365 and 366 had to contend with an uprising by Procopius, the last surviving member of the Constantinian Dynasty. Valens easily put down Procopius and the Dynasty was no more. In 391, the Emperor Theodosius I officially declared that Christianity was the state religion of Rome and for the first time, fully outlawed paganism. There would never again be a pagan Emperor and the Greco-Roman religion was driven almost completely underground.
How did Christianity get so entrenched in the Roman ruling class that within less than a century, paganism got banned outright? There are a few theories, including Julian's own about the sympathy that observers felt for the martyrs. I feel that Christianity served different functions for each of the three relevant classes in Roman society: the plebs, the nobles, and the military. Christianity appealed to the plebeian class because it stressed the virtue of poverty and humility. Christianity gained many converts during the third century largely as a result of the chaos that befell the Empire; sure, things suck now, but this is your station in life and if you deal with it for just a little bit longer, things will be so much better once you leave your physical body. For the upper classes, converting to Christianity was the natural thing to do if you wanted to gain favor with the Emperor. Constantine and Constantius II gave Christians high-ranking jobs in their bureaucracies well above their proportion to pagans. Want an important job? Do the politically expedient thing and convert. The hardest class to dislodge from paganism was the Roman army. The Roman army was, by this time, not really even Roman: it was comprised mainly of Germanic allies. The type of Christianity that caught on with the army emphasized struggle, toughness, and loyalty, carrying a decidedly Stoic or even Spartan tone.
The effects of the Christianization of the Roman Empire are obvious: had Constantine never adopted it as his personal religion, there's a very strong likelihood that Christianity wouldn't be the world's most populous faith (though Islam is sure to overtake it within the next hundred years or so). I'm not going to pontificate or moralize about the positive or negative effects of this, but it's clear that many writers (like Edward Gibbon and Oswald Spengler) viewed the advent of Roman Christianity as one of the chief reasons that the Empire collapsed. Whether or not this is the case is debatable, but the important thing to remember is that the Roman Empire didn't collapse in 476 as is commonly believed; in all actuality, it underwent a change of management. The greatest legacy of the Constantinian Dynasty, aside from the advent of Christianity, is the fact that by moving the center of the Empire from the West to the East, it survived up until the middle of the 15th century.
Crisis of the Third Century | Constantinian Dynasty | Valentinian Dynasty