yum! If what was said in an earlier post about the Roman empire being divided into three parts with there being the Western, the otl Eastern which might end up being called the middle, and the far eastern which would be Mesopotamia, Persia, maybe parts of Arabia, and if later down the line they want to go on and try some conquering to the east they might be able to conquer a bit of the Indus river region.
An empire divided into three parts is interesting. But I could imagine that the middle part would play the most important rule, because it has the most valuable territory (Egypt, Asia minor, the Danube provinces) under its control, while the eastern empire (Persia) and the western one (Rome and Gaul) can't beat the middle empire alone. If they unite to conquer it, they still can't rule it and will have to carve it up into three empires a second time.
Balkanize it by bringing in as many disparate groups into the area as possible.
That's a good idea! I'll think about it.
First off,the tradition of an army proclaiming any successful general emperor still hasn't set off,this is critical,since this means that the emperor still doesn't need to directly lead his armies on every front.Secondly,the army has been segregated from civil governance,this reduces the ability for generals to rebel.Third,Rome is still rich,it can afford to pay it's army well.Fourth,as I've mentioned,it's time to neuter the army--demobilize most of the regular army into part-time soldiers paid by land use and consolidate what's left over of the regular army into the comitatus--it's a much cost effective method than having a regular army often with nothing to do but fight other legions.Finally,Rome's enemies are nowhere near as powerful as they were in OTL,so the necessity of having multiple emperors isn't mandatory.
Yes,
@darthfanta, principally you're right. The Spanish Empire was much greater and had enemies of comparable strength and a similar technology. However, it was governed from Madrid (with some viceroys in the colonies), so the Roman Empire, even with Mesopotamia, can be governed from one city. But I don't know if we can convince
@Agricola. Do you think so

?
thx, and if they put the limes along the Elbe instead of the Rhine then they would probably have much better luck dealing with Germanic hordes.
Yes, the Agri Decumates were already extended and the Alemanns defeated, and a campaign against the growing power of the Franks is now necessary. Though, once the Franks are submitted, only the Langobards, Burgundians, Saxons and the Vandals would remain as powerful enemies of the Romans in the west - not an insurmountable difficulty.
And if they're at the Elbe perhaps they could give conquering Jutland a try? It seems very unrealistic but Jutland is flat enough for agriculture and is easily defensible (see: Danevirke) and going back to the flat part means that the Roman Legions would easily cut through tribes who do not yet know of Rome's effectiveness on the open field.
If the Romans can deal with the Franks, the Saxons in Jutland shouldn't be a great problem.
Of course they might need a heavy plow for farming that far North and unless someone in the Roman controlled Germania gets an Idea or something it won't be possible.
Then again, the Idea of a heavy plow might not be so far fetched if Governors in Germania try and get people to work out solutions to make their province(and by extension them) more wealthy and some grain to sell to the army would certainly bring in the big bucks.
The heavy plow is in the air, it just needs to spread. But the task in Germania is much more serious: Clear the woods, pacify the tribes, build roads, establish an administration... The Romans need to start from zero and try not to repeat Varus' mistakes.
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Caput Vicesimus Septimus: The Rise of the Goths
The Severan Dynasty was an African family of Phoenician origin. They were focused on warm regions, and concentrated on southern and eastern regions. But even if we prefer speaking of beautiful and exotic cities, we have now to turn our attention to the Danube, away from the golden cities of the Orient.
Indeed, a new threat had emerged in the north – it seemed that tribes and peoples unheard until then had set into motion: Did the Barbarians finally unite in a common scheme to destroy civilization? Some Roman philosophers thought so, and their theory was soon taken up by Buddhist monks who preached indifference to the present and caused some serious trouble within Rome.
In the meantime, the Goths had arrived on the Black Sea and had become a problem on the Dacian border. Histria in Moesia had been sacked in 989 AUC [1], Marcianopolis in 994 AUC [2]; most importantly, a large invasion of Dacia, lead by the Gothic paramount leader Kniwa, caused great damage on both banks of the Danube. The Goths could only be stopped with great difficulty by General Decius in the Battle of Apollonia in 1004 AUC [3], and the Romans couldn't achieve more than a temporary peace.
This period of rest allowed the Romans to concentrate on the east and win the First Persian War. But the demographic pressure on the Gothic leadership was too high and the resources of the steppe too scarcely distributed for a durable peace. Soon, the gafaurds (council) overthrew Kniwa and replaced him with Cannabaudes, who became the new Judge of the Goths (kindins).
Because they encountered Roman resistance on the Danube, the Goths marched to the east and raided the Kingdom of the Cimmerian Bosporus, where they conquered several Greek colonies and seized the Bosporan shipyards.
Officially, the Goths were only allies of the Bosporan King Tiberius Julius Rhescuporis IV [4], himself a vassal of the Roman Emperor. But in fact, the Bosporans were completely helpless against the Gothic menace. Thus, the Gothic tribes (as well as their allies, Heruli and Roxolanes) became the new overlords of the Tauric Chersonese, and the desultory measures of the Roman military didn't change much.
New Gothic raids were to be expected.
[1] 236 CE (as in OTL)
[2] 241 CE (as in OTL)
[3] 251 CE
[4] An OTL king (BTW: I love this name)
Military action in the Black Sea, opening moves