So let's take an idea I suggested as a counter-example in another thread. Suppose Vespasian came up with this system of "Choose the oldest son, if no sons, chose the son-in-law married to the oldest daughter. If someone is dead, their children 'take their place' in succession. Use me as the 'root' of the hereditary system" and suppose for the sake of argument no one questions this for his lifetime. Suppose the Senate ratifies this and no one questions this during his reign, Titus, and Domitian.
Suppose Domitian has 3 sons, and the oldest inherits without a fuss. And that guy also has a son (Vespasian's great-grandson). And all 5 of these Emperors are gifted administrators, all charismatic, and all good tacticians (good luck when the last guy grew up in a palace).
Originally I pointed out this unlikely series of events was the best case scenario for a particular goal someone else wanted and still wouldn't likely achieve that goal, but we're not trying to get to that goal, but see where the sequence of events goes.
Suppose Rome never is divided. Rome or Mideolanium remain the seat of power. Due to the butterfly effects, Vespasian's successors co-op the Suedbi, the Burgandians, and the Ostrogoths as allied mercenaries. The denarii is not debased beyond Vespasian's time. Many other barbarians are shoved back beyond the Rhine (If this sounds implausible, remember that OTL Rome had the numbers and resources available to do so, but they spent lots of time infighting like Constantine III vs Honorius and corruption sapped the government coffers) The Visigoths are exterminated. The Huns easily defeat boarder units of ripenes, but in three separate field battles they are given checks by the Comitantesis.
After the Huns are dealt with, the Romans prop up "friendly Germans" kings to replace "descendants of stupid barbarians who keep trying to settle on Roman lands when running away from the Huns" in the most fertile areas East of the Rhine, as kind of a Sphere of Influence. Roman Britain is given a fresh security upgrade, either turning Hadrian's Wall into a super fortification, turning the Picts into a tributary state, or getting the Picts to stop bugging them.
Internal threats, threats to Britain, and threats from the Rhine have been suppressed. No one is invading from the Atlantic obviously. The Sinai in Egypt and the Balkans in the north provide natural barriers on both sides of the Mediterranean.
What would a likely outlook by 800 be?
Would Rome survive to 800 having defeated internal threats, threats to Britain, and threats from the Rhine in the 400s? We might see a Muslim invasion take Egypt. Or maybe an Arabic pagan invasion. If modern day Egypt and Tunisia (Tunisia was a forested land with fertile clearings back then not a desert), it would seriously destabilize Rome and make the Emperors lose prestige, perhaps making ambitious generals think they can do better.
Assuming Rome survived
What would be seen on boarders? A huge series of forts similar to OTL castles? An open boarders with trade going both ways? A few large forts that house over a thousand legionaries apiece backed by super Euites/Equites Promoti (equestrians, basically the new knights as cavalry becomes better)?
How about religion? Would the persecutions of Christianity stop with the deviations, since in OTL Vespasian did not have a great grandson sitting on the throne? The OTL banning of Christianity was a very unusual event because in those days people respected each others' gods (even if they failed to worship foreign ones) and the Emperors considered that the Christians would be a subversive threat, more loyal to their god than Emperors (oddly enough, the Jewish revolt was responded to "merely" by sacking and scattering them, but not a religion bad). Would Christianity hijack a Emperor, or is a civil war the only way to convert the throne?
How about language? A plurality of Romans spoke Latin, but Romans gave citizenship to so many of their people that it's actually a minority. In particular less than 1/4 of the citizens in the Eastern Half or in Roman Britain spoke Latin. There was no policy of Latinization either. Greek in fact I think was considered a prestigious language.
How about slavery? To the Roman perspective it worked. There was a nasty Socii Wars which resulted in the banning of enslaving Romans, but that didn't stop them from enslaving conquered people or simply buying them from outside. So in TTL, assuming Rome survived, I don't see it being done away. In OTL it was gone in France by 800 wasn't it?
How about marriages for the Imperials? Romans marrying non Romans was acceptable. However, marrying a foreign sovereign (like Cleopatra) was not acceptable. Likewise, the Imperial family married within the Empire for the sake of appearing properly Roman.
Suppose Domitian has 3 sons, and the oldest inherits without a fuss. And that guy also has a son (Vespasian's great-grandson). And all 5 of these Emperors are gifted administrators, all charismatic, and all good tacticians (good luck when the last guy grew up in a palace).
Originally I pointed out this unlikely series of events was the best case scenario for a particular goal someone else wanted and still wouldn't likely achieve that goal, but we're not trying to get to that goal, but see where the sequence of events goes.
Suppose Rome never is divided. Rome or Mideolanium remain the seat of power. Due to the butterfly effects, Vespasian's successors co-op the Suedbi, the Burgandians, and the Ostrogoths as allied mercenaries. The denarii is not debased beyond Vespasian's time. Many other barbarians are shoved back beyond the Rhine (If this sounds implausible, remember that OTL Rome had the numbers and resources available to do so, but they spent lots of time infighting like Constantine III vs Honorius and corruption sapped the government coffers) The Visigoths are exterminated. The Huns easily defeat boarder units of ripenes, but in three separate field battles they are given checks by the Comitantesis.
After the Huns are dealt with, the Romans prop up "friendly Germans" kings to replace "descendants of stupid barbarians who keep trying to settle on Roman lands when running away from the Huns" in the most fertile areas East of the Rhine, as kind of a Sphere of Influence. Roman Britain is given a fresh security upgrade, either turning Hadrian's Wall into a super fortification, turning the Picts into a tributary state, or getting the Picts to stop bugging them.
Internal threats, threats to Britain, and threats from the Rhine have been suppressed. No one is invading from the Atlantic obviously. The Sinai in Egypt and the Balkans in the north provide natural barriers on both sides of the Mediterranean.
What would a likely outlook by 800 be?
Would Rome survive to 800 having defeated internal threats, threats to Britain, and threats from the Rhine in the 400s? We might see a Muslim invasion take Egypt. Or maybe an Arabic pagan invasion. If modern day Egypt and Tunisia (Tunisia was a forested land with fertile clearings back then not a desert), it would seriously destabilize Rome and make the Emperors lose prestige, perhaps making ambitious generals think they can do better.
Assuming Rome survived
What would be seen on boarders? A huge series of forts similar to OTL castles? An open boarders with trade going both ways? A few large forts that house over a thousand legionaries apiece backed by super Euites/Equites Promoti (equestrians, basically the new knights as cavalry becomes better)?
How about religion? Would the persecutions of Christianity stop with the deviations, since in OTL Vespasian did not have a great grandson sitting on the throne? The OTL banning of Christianity was a very unusual event because in those days people respected each others' gods (even if they failed to worship foreign ones) and the Emperors considered that the Christians would be a subversive threat, more loyal to their god than Emperors (oddly enough, the Jewish revolt was responded to "merely" by sacking and scattering them, but not a religion bad). Would Christianity hijack a Emperor, or is a civil war the only way to convert the throne?
How about language? A plurality of Romans spoke Latin, but Romans gave citizenship to so many of their people that it's actually a minority. In particular less than 1/4 of the citizens in the Eastern Half or in Roman Britain spoke Latin. There was no policy of Latinization either. Greek in fact I think was considered a prestigious language.
How about slavery? To the Roman perspective it worked. There was a nasty Socii Wars which resulted in the banning of enslaving Romans, but that didn't stop them from enslaving conquered people or simply buying them from outside. So in TTL, assuming Rome survived, I don't see it being done away. In OTL it was gone in France by 800 wasn't it?
How about marriages for the Imperials? Romans marrying non Romans was acceptable. However, marrying a foreign sovereign (like Cleopatra) was not acceptable. Likewise, the Imperial family married within the Empire for the sake of appearing properly Roman.