Isoroku295

Which system was better? Having the Legions on the border to straight up form a wall? Or to have the Limitanei slow down the enemy and then let the break through into the Empire to be beat by the formed up Comitatenses? Or is it a matter of the times?

Regardless after answering, what is the advantages and disadvantages?

Salah

I see little reason to believe that battle tactics changed to any significant degree between the early and later Empires.

Sargon of Akkad

I think he means the large legionary armies of the late republic/early empire or the light auxiliaries and sole cavalry forces that later were used to patrol the borders with, with a single large legionary army under the command of the emperor.

Isoroku295

Not really. At first you have these large Roman Legions who would go out and as soon as possible deal with the enemy. In the Later Empire (Like Byzantium) you had the Limitanei on the frontiers who would assembly and simply slow the enemy and then let them through after the Comitatenses formed up, then those would wipe out the enemy.

So essentially the Later Empire used a holding move then brought up soldiers stationed away from the border, while the Earlier Empire used Legions on the border that would defeat the enemy as soon as possible.

Salah

I think the Late Imperial system would have been better, had other circumstances been more favorable.

Sargon of Akkad

Er, isn't that exactly what I just said?

p,c,ma

In the early days your enemy was easy to identify and fight. In the later days(like Byzantium) the enemy was usually just small raiding parties. So it really depends who you are fighting at the time.

Isoroku295

maybe. I might have misread your post

spqr95

Luttwalk discussed this in his book: "The Grand Strategy of the Roman Empire", though critics disagree whether there was a coherent policy or just an evolution of the army in response to internal and external factors.

pikeshot1600

I would argue that the military policy of the Empire - certainly after the second century - was entirely reactive and defensive. Mostly the extent of territory and the slowness of communications made it so. There does not appear to be a difference between military and "foreign" policy in the imperial centuries. There was no "foreign office."

Internal politics and civil wars in the third century also drained much energy and many resources from the limits of the Empire in the north. The Northern Peoples were not yet in a position to take full advantage of that, but by 400 it all changed (as did the Northern Peoples).

In the north, as early as the first century, the north - the Rhine and Danube Rivers - became a defensive "line," more rigid before the Dominate, and a defense in depth under the Constantines. The worth of or liability of Britain to the Empire is stiil a subject of debate

In the east, attempts to extend Imperial control to Mesopotamia in the third century were failures, with several defeats and humiliations suffered against Persia. Persia was in the same situation, and neither of them was able to do anything against the other except to slug it out on their peripheries. The eastern territories became a defensive buffer between Persia and the Levant.

The grand strategy was mainly to "hold on to what ya got, and fight who wants to take your stuff." They didn't need a foreign office for that.