Just something I whipped together while driving around today, thinking about Roman history, trends, and Star Trek:
Thats all I got. I figure the Slavs, Arabs, and Norse are pretty much going to happen in some form or another, so they get caught up by the butterfly nets and still wreck havoc on this world. Further than that, I don't want to extrapolate off the seat of my pants.
Many students use the maxim 'Even Good, Odd bad' to remember the events of Roman history. This is a rudimentary technique, and gravely oversimplifies history, but it does serve its purposes for a large stretch of the Empire's history.
It starts with the Second Century, when the Five Good Emperors ruled over Rome in what is one of the longest stretches of internal peace any state has ever known.
This devolved in the Crisis of the Third Century, kicked off by the Antonine plague, the chaos and disorder after the death of Commodus, and the failed attempted at restabilizing by the Severans, which lead directly to the Barracks Emperors, who were hard pressed on all sides to maintain the Empire. Indeed, it came very close to crumbling.
The efforts of first, Diocletian, and then, Constantine, in the Fourth Century, were able to set the Empire back on its feet, and, while that era fell short of the Antonine achievements, it made significant progress over the prior century.
All that was close to undone in the Fifth Century, as the various Germanic tribes, pushed ever westward and southward by the Huns, poured over the increasingly porous borders of the Empire. Indeed, until the exploits of Majorian, it looked very much like the Empire might fall apart completely in the West. However, it lingered on, though in a state of constant chaos as it struggled with the fiercely independent autonomous Germanic states within its borders.
It would be during the Sixth Century that the West truly restabilized, and the various Germanic elements were successfully incorporated into the Roman identity, and the borders re-established at their prior frontiers. For much of this century of relative peace, the Empire was even reunified in its administration, though pressures by the Saxons, Lombards, and Avars encouraged the redivision of the Empire to handle the external threats, and they were handled acceptably well.
It was near the dawn of the Seventh Century, after those threats had greatly receded in their threat to the Empire that, once again, chaos fell upon the Empire. Plague, which had struck the Mediterranean from time to time Sixth Century, descended upon Rome with a new ferocity just as that century ended. Combined with this, the Persian Wars flared up with an entirely new ferocity, as the Eastern Empire was attacked both by the Persians and by the newest arrivals to its European frontiers: the Slavs. It required concerted and coordinated efforts by both Roman Emperors, across multiple administrations to push back the invaders and retake many lost provinces, only for a new threat to erupt out of the Arabian peninsula, as the fierce desert nomads banded together to take advantage of their weakened neighbors.
When the Eighth Century began, the Eastern Empire looked just as bad as the West had in the Fifth Century, with its valuable Syrian and Egyptian territories gone, and the West was not much better, having lost Africa and portions of Hispania. However, the cohesion that had held the invading Arabs together broke down as they settled amongst the conquered peoples and adopted their culture and religion, and as their recent conquests in Persia became too unruly to maintain. As infighting began amongst them, the Romans were able to pick off territories, one by one, sometimes by force, sometimes by diplomacy. Before the midpoint of the century, the Empire was totally under Roman control once more.
It was the Ninth Century that brought the fierce Norse raiders to the coasts of Britannia and Gallia, settling in large numbers in the wake of their raids, and even extending their terror to the East, with raids in Anatolia and along the Danube.
The Christianization of those seafarers in the Tenth Century is considered by many to have tamed them, but, more important was the assimilation of the Norse states within Gallia and Britannia, so similar to their Germanic predecessors centuries before, in bolstering Roman military defenses against the raiders.
Thats all I got. I figure the Slavs, Arabs, and Norse are pretty much going to happen in some form or another, so they get caught up by the butterfly nets and still wreck havoc on this world. Further than that, I don't want to extrapolate off the seat of my pants.