Jovian, like his father before him, was an imperial bodyguard. And he was a Christian, which means the anti-Christian Julian was either willing to employ Christians as long as they didn't act all You Should Be A Christian Too, or Jovian (and everyone else who believed in Jesus) kept his faith a secret.
Jovian wasn't anyone's first choice for emperor following Julian's death. The officers originally offered the position to an old Praetorian who, after considering what a lousy job being emperor actually is, respectfully declined. Jovian, having no such inhibition, accepted the job as soon as it was offered.
It turned out that most of the troops misheard the announcement. Some of them, apparently, heard the name "Jovian" as "Julian" and thought the Apostate had recovered from his wound. Others thought they'd announced that a notable notary named Jovianus had been chosen. Instead of either of those men, they got Jovian.
If you'll recall, all of this took place in 363, in the middle of a large military expedition against the Persians. And things hadn't been going well. In fact, Julian was leading the army on a strategic retreat when he was fatally struck down. Jovian's first task was to complete the retreat, and he secured safe passage for the Roman forces by paying the Persians a bunch of cash and agreeing to give back a bunch of land. Under the circumstances, this was probably the wisest thing to do, but it made Jovian unpopular.
Another thing that made Jovian unpopular was when he burned down the Library of Antioch. He meant it to be a strike against paganism, but Christians (the literate ones who were keen on books) didn't like it anymore than the pagans.
But Jovian didn't end up having much opportunity to leave a lasting impression on anyone; in 364, whilst en route to Constantinople, he died of carbon monoxide poisoning from a fire he'd kindled in his tent.
The next man up was Valentinian I, commonly thought of as the last great western emperor.
He accepted the position, elevated his brother Valens to co-emperorship, and (per custom) split the empire into two parts. Valentinian I set up court in Milan and controlled the West. Valens set up in Constantinople and controlled the East.
Valentinian I spent all of his time fighting Gallic raiders and Sarmatians and the Quadi. In 375, a group of Quadi met with Valentinian I to parlay. Valentinian I, an intemperate man given to frequent outbursts of anger, found their attitude to be so insolent and discourteous that he flew into a rage:
..and then promptly had a stroke and died.
Meanwhile, Valens was doing his best to keep things together in the east.
He'd had to put down a revolt led by Julian's cousin (Procopius) and Gothic tribes were starting to to move into Roman territory in order to escape the Huns. Valens thought the best thing to do would be to let some of them settle in Roman territory. But the local Roman officials mistreated the foreigners and, in response, the tribesmen banded together into a formidable army (mostly Visigoths and Ostrogoths) and eventually met Valens in battle. At Hadrianople in 378, Valens took an arrow in the face...
...and died along with more than half of the Roman forces in the eastern army.
Now, around the year 367, Valentinian I promoted his son Gratian (aged 8) to the rank of junior emperor with him in the west. When Valentinian I died of a stroke, Gratian (now aged 16) took over the job of western emperor.
Valentinian's other son, the 4-year-old Valentinian II was named Gratian's juior emperor.
VALENTINIAN II 375-392
Gratian, in matters of religion, was led by Ambrose, the inordinately powerful Bishop of Milan. He set out to repress paganism, famously removing the Altar of Victory from the Roman senate house.
In Britain, a Roman general named Magnus Maximus revolted against the unaccountably unpopular Gratian and led the army down to attack Roman Gaul. Gratian's men abandoned him and he was captured and killed at Lyons in 383.
Remember when Valens died in 378? That's when Gratian named Theodosius I, a Spanish officer, emperor of the east.
THEODOSIUS I 379-395
So, just to be clear, we now have Valentinian II in the west and Theodosius I in the east.
The young Valentinian II was now the sole emperor of the west but found himself dominated by a man named Arbogast, the commander of his armies. Valentinian began to resent Arbogast and attempted to dismiss him from his position. Arbogast, unmoved, replied, "You can't fire me because I don't work for you. I work for Theodosius."
And shortly thereafter, Valentinian was found hanged.
Arbogast, really feeling himself at this point, decided to nominate a former grammar & rhetoric teacher named Eugenius (known to posterity as "The Usurper") for the position of emperor of the west.
EUGENIUS THE USURPER 392-394
Eugenius was a Christian, but he used public money to support pagan building projects which put him at odds with Theodosius I who, in 391, outlawed paganism and declared Christianity the official religion of the Roman Empire. Theodosius killed Mag Max in 388 and in 394 he made time to kill Eugenius and Arbogast. But before that, Theo had all kinds of adventures. In 382, he signed a peace treaty with the Visigoths which allowed them to occupy Roman territory under the authority of their own king. In 390, he massacred a bunch of Thessalonian citizens after they killed one of his commanders. Ambrose, Bishop of Milan was so incensed by this act of violence that he formally excommunicated Theodosius and wouldn't let him back into the church until he'd repented by sitting outside the church and crying for 8 months.
Theodosius died from severe edema in 395 and left the empire to his two sons; Arcadius (17 yrs) was given the eastern half and Honorius (10 yrs) was given the western half.
Let's get Arcadius out of the way first.
There's not a whole not to say about him. He wasn't an especially effective emperor and was controlled by ministers and eunuchs and his wife, Eudoxia. In 399, he issued an edict that called for the demolition of all remaining pagan temples.
Arcadius died in 408 at the age of 31.
Now, on to Honorius.
Honorius was only a boy when he became emperor of the western half of the Roman Empire and, as such, he fell under the guardianship of his general, Stilicho. Around 401, Alaric, king of the Visigoths, began raiding Italy and Stilicho managed to push him back. Honorius, convinced that Stilicho was plotting to overthrow him, had Stilicho arrested and executed and when Alaric returned in 410 he was able to successfully march all the way to Rome. And when he arrived, he sacked the city.
Rome hadn't been sacked since about 390 BC. The emperor's court was no longer located in Rome (it had moved on to Ravenna), but the fact that Rome was sacked was unimaginable. The whole thing really gave Honorius' reign a black eye.
He spent the rest of his reign dealing with the fallout from the sack of Rome, fighting against rebellion, and trying to make deals with the various tribes and people groups invading the western empire.
In 423, Honorius died of edema and the unstable empire was juggled between the hands of Theodosius II, Johannes (the other Usurper), and Valentinian III.
Be sure and come back next time to find out if the empire is able to get back on its feet!
(it isn't able to get back on its feet, it just falls apart completely)