Why did Romans/Byzantines not finish Persians whenever they took Ctesaphion

Nov 2012
3,852
#1
Why did the Romans not finish off the Persian empires when they repeatedly captured the capital city Ctesaphion and even took some royals hostage. Why did they not press on further and finish of the Iranian kingdoms like the Arabs did later. Why did they allow the Persians to survive when they could have delivered a knockout blow. It seems like both Persians and Byzantines were interested in their peripheries of their empire rather than take each others heartlands. It seems like they were enemies only upto a certain point and did not want to extinguish each other. Why else would this happen?
 

Ichon

Ad Honorem
Mar 2013
3,654
#2
Geography and supply lines. Ctesaphion was exposed and easily captured while Persian heartlands were easier to defend and more difficult to attack.
 
Jul 2013
940
Melbourne
#4
There movement of an ancient army was not like it is in Rome totalwar; the ability to feed and water an army from local resources was always a limiting factor upon operations. This was even more important in Mesopotamia and the middle east because of the vast tracts of parched desert to the south and nearly impenetrable mountains to the east. This effectively limited the routes any army could take between the Roman and Persian sphere's to three: the two direct axis which followed the Tigris or Euphrates are essentially highways between the great Roman eastern metropolis of Antioch and Ctesiphon, and a northern axis through Armenia, which is very long and contains multiple mountain passes. Thus the most used axis of attack for either Roman or Sassanid armies was the direct rout along the Tigris/Euphrates. Thus in the second century it was relatively easy for Roman armies to simply march down the rivers to Ctesiphon, and the Sassainians took Antioch relatively easily in the third.

Persia sits in a high plateau, which is effectively surrounded by mountains, and its also massive. Thus taking Ctesiphon is a very, very different problem in comparison to projecting an army into the Persian plateau, which leaves the well established lines of communications along the rivers and canals of Mesopotamia. So just as though it was pretty much impossible for a Sassanid army, even though it may have taken Antioch, were never going to threaten Rome, it was very unlikely that a Roman army, even if they had taken Ctesiphon, to drive through the mountains to the east.

As we get into the 'Byzantine' period, both the Eastern Romans and the Sassanians heavily fortified these three possible axis of attack. This process actually began under Diocletian. The massive fortified cities such as Nisibis made this one of the most fortified borders in the world at the time. Thus it became harder and more costly to invade either the Roman East or Mesopotamia. The combination of the logistics involved, the defensibility of the approaches to the Iranian plateau and the vast area we are talking about made a Roman army conquering Persia proper extremely difficult.

And did Romans/Byzantines capture Persia proper at any point of time.
Nope.
 
Jun 2013
2,361
--
#5
There movement of an ancient army was not like it is in Rome totalwar; the ability to feed and water an army from local resources was always a limiting factor upon operations. This was even more important in Mesopotamia and the middle east because of the vast tracts of parched desert to the south and nearly impenetrable mountains to the east. This effectively limited the routes any army could take between the Roman and Persian sphere's to three: the two direct axis which followed the Tigris or Euphrates are essentially highways between the great Roman eastern metropolis of Antioch and Ctesiphon, and a northern axis through Armenia, which is very long and contains multiple mountain passes. Thus the most used axis of attack for either Roman or Sassanid armies was the direct rout along the Tigris/Euphrates. Thus in the second century it was relatively easy for Roman armies to simply march down the rivers to Ctesiphon, and the Sassainians took Antioch relatively easily in the third.

Persia sits in a high plateau, which is effectively surrounded by mountains, and its also massive. Thus taking Ctesiphon is a very, very different problem in comparison to projecting an army into the Persian plateau, which leaves the well established lines of communications along the rivers and canals of Mesopotamia. So just as though it was pretty much impossible for a Sassanid army, even though it may have taken Antioch, were never going to threaten Rome, it was very unlikely that a Roman army, even if they had taken Ctesiphon, to drive through the mountains to the east.

As we get into the 'Byzantine' period, both the Eastern Romans and the Sassanians heavily fortified these three possible axis of attack. This process actually began under Diocletian. The massive fortified cities such as Nisibis made this one of the most fortified borders in the world at the time. Thus it became harder and more costly to invade either the Roman East or Mesopotamia. The combination of the logistics involved, the defensibility of the approaches to the Iranian plateau and the vast area we are talking about made a Roman army conquering Persia proper extremely difficult.
Excellent post.

I think the Byzantines were also already exhausted, otherwise Heraclius wouldn't have started negotiating a peace treaty in the first place.
 
Jul 2013
940
Melbourne
#6
I think the Byzantines were also already exhausted, otherwise Heraclius wouldn't have started negotiating a peace treaty in the first place.
Both the Sassanids and the Byzantines were exhausted, the seventh century really was horrendous for Romano-Sassanid relations. Nearly a century of very destructive war fatally weakened both powers.
 
Feb 2011
1,595
#7
The Romano-Persian conflict was perhaps the most static in military history. In six centuries of warfare, the border changed only little. The very last war was very untypical in that both powers penetrated deep into foreign territory; mostly, the campaigns were limited to the half-arc from Upper Mesopotamia to Upper Syria or in the Armenian highlands.
 
Mar 2011
5,047
Brazil
#8
There movement of an ancient army was not like it is in Rome totalwar; the ability to feed and water an army from local resources was always a limiting factor upon operations. This was even more important in Mesopotamia and the middle east because of the vast tracts of parched desert to the south and nearly impenetrable mountains to the east. This effectively limited the routes any army could take between the Roman and Persian sphere's to three: the two direct axis which followed the Tigris or Euphrates are essentially highways between the great Roman eastern metropolis of Antioch and Ctesiphon, and a northern axis through Armenia, which is very long and contains multiple mountain passes. Thus the most used axis of attack for either Roman or Sassanid armies was the direct rout along the Tigris/Euphrates. Thus in the second century it was relatively easy for Roman armies to simply march down the rivers to Ctesiphon, and the Sassainians took Antioch relatively easily in the third.

Persia sits in a high plateau, which is effectively surrounded by mountains, and its also massive. Thus taking Ctesiphon is a very, very different problem in comparison to projecting an army into the Persian plateau, which leaves the well established lines of communications along the rivers and canals of Mesopotamia. So just as though it was pretty much impossible for a Sassanid army, even though it may have taken Antioch, were never going to threaten Rome, it was very unlikely that a Roman army, even if they had taken Ctesiphon, to drive through the mountains to the east.

As we get into the 'Byzantine' period, both the Eastern Romans and the Sassanians heavily fortified these three possible axis of attack. This process actually began under Diocletian. The massive fortified cities such as Nisibis made this one of the most fortified borders in the world at the time. Thus it became harder and more costly to invade either the Roman East or Mesopotamia. The combination of the logistics involved, the defensibility of the approaches to the Iranian plateau and the vast area we are talking about made a Roman army conquering Persia proper extremely difficult.
Alexander, with much smaller resources than Rome, conquered Persia proper and at a time when Persia was significantly more powerful (in absolute terms actually) than during Roman times. It doesn't appear to me that Rome lacked the resources to conquer Persia if they seriously wanted to do it. They did not conquer it because they did not want to conquer it.

Rome was a more practical than Alexander in terms of conquests. They only conquered lands which were profitable conquests, regions that could pay the taxes to support the city of Rome and Italy (which did not pay any taxes to the central government, though local civitates had their own taxes). Conquering Britain was already a technical waste of resources and Rome left Germany also because it was a waste of resources: Germany was too poor to be worth conquering, setting up the border at the Rhine would be easier to defend. Conquering the Persian plateau would be an even greater waste of resources, geographical considerations were important but note that Trajan claims he did not advance further due to his own advanced age. In terms of logistical, military capabilities Rome at the time of Trajan was such tremendously powerful empire that they could do pretty much anything they wanted to.

Also, Roman armies used long logistic lines at least when operating in the Mediterranean. The much higher cost of land transportation was certainly a limiting factor in the penetration of Persian territories besides the low population densities and low agricultural output of these areas (hence, limited local resources).
 
Last edited:
Mar 2011
5,047
Brazil
#9
The Romano-Persian conflict was perhaps the most static in military history. In six centuries of warfare, the border changed only little.
It wasn't a continuous conflict and the situation was very different across different periods of time.

The very last war was very untypical in that both powers penetrated deep into foreign territory; mostly, the campaigns were limited to the half-arc from Upper Mesopotamia to Upper Syria or in the Armenian highlands.
That's because before (up to the late empire period) Rome was an hyperpower who wasn't seriously interested in conquering Parthia/Persia. That region was in decline for a long time period, in fact, Persian agricultural output, population levels and tax revenues all peaked during the Achaemenid/Seleucid period and never returned/surpassed those peak levels up to the late 19th century. By Roman times it was mostly a barbarian wasteland which Rome had no benefit in conquering.