Roman Defense of the Zagros?

You misjudge the ferocity of Roman civil wars. The Limitanei were specifically formed to prevent political implosions from stripping the borders.
But you said yourself the limitanei was not very good at stopping more then raids. Also aren’t field armies kept a bit further away then right at the border? If we are really going for the romans having the same type of army as they did in the otl late Empire wouldn’t the field army be kept further away but because the Persian couldn’t cross the mountain as easily there armies would be smaller nessitaing a smaller field Army in the east?
 
The mountains themselves are a decent barrier, if the maps I've seen of Persia's Royal Roads is any indication there's only two passes suitable to a high volume of movement. However Rome would need some awkward borders to keep a defensible border as there's a large flat low land in Khuzestan/Bushehr that cuts the mountains off from the coast. There's also the problem that the Zargos mountians share with proposals for Rome holding the Carpathians, they're mountains not rivers. They're much harder to supply and reinforce as they are natural barriers rather than highways.

The Tigris or Euphrates would be much more optimal as it goes right from the Anatolian highlands to the gulf and makes logistics a piece of cake.
The Zagros are just next to one of the most fertile plains on earth.Places with worse logistic problems have been defended.
 
But you said yourself the limitanei was not very good at stopping more then raids. Also aren’t field armies kept a bit further away then right at the border?
Sigh
Yes. Thank you for finally coming to the conclusion that field armies won't be guarding the mountain passes. Meaning that pitch battles will still take place west of the Zagros, negating any advantage that they would have as the official borders. Also once you get beyond the foot hills of the Zagros you're in the exact terrain that the Parthian and Sassanian armies were made for. Not only would a river frontier make the Roman response much quicker, but it would also shift the field of battle to the marshy lands of Mesopotamia, which would be much more similar to the fields of battle that Roman Field Armies specialized in.

If we are really going for the romans having the same type of army as they did in the otl late Empire wouldn’t the field army be kept further away but because the Persian couldn’t cross the mountain as easily there armies would be smaller nessitaing a smaller field Army in the east?
There are two major trade routes through the Zagros, they aren't going to prevent the Persians from fielding large armies.

The Zagros are just next to one of the most fertile plains on earth.Places with worse logistic problems have been defended.
Feeding an army is one part of logistics, moving an army is the part I'm more concerned with. With a Zagros border, for a legion stationed in the north to assist a legion in the south it would have to march west all the way to Mesopotamia, take a boat down the Tigris, then then get out of that boat and march east meet up with (whatever remains of) the southern legion.* With a Tigris border they simply get in their boats and go right to the site of the incursion.

*they have go back to Mesopotamia because and army marching 1,500 km through a mountain range is logistically impossible even with modern technology.
 

FYI, that just comes off as rude.

Yes. Thank you for finally coming to the conclusion that field armies won't be guarding the mountain passes. Meaning that pitch battles will still take place west of the Zagros, negating any advantage that they would have as the official borders. Also once you get beyond the foot hills of the Zagros you're in the exact terrain that the Parthian and Sassanian armies were made for. Not only would a river frontier make the Roman response much quicker, but it would also shift the field of battle to the marshy lands of Mesopotamia, which would be much more similar to the fields of battle that Roman Field Armies specialized in.

That conclusion is still not at all accurate. Any fortification that is in place in those passes will make advancing nearly impossible. As long as you have a strong fort and a healthy reserve of supplies, and a way to ensure they can alert any deployed forces that they need relief. Even if it is just giant flaming beacons. More or less like any border fortification. An invading army that tries to ignore that fortification is in trouble.

In addition, having forces on the river itself leaves those spaced out forces in danger. Sure when the news gets out there can be forces deployed, but a rapid campaign could take out field armies piecemeal, and threaten Roman supply lines, leaving them in a precarious position whilst waiting for reinforcements.

There are two major trade routes through the Zagros, they aren't going to prevent the Persians from fielding large armies.

This is true, but it does limit how affordable they are - simply because of the more secure Mesopotamian cities (although I fear I've said as much before).

Feeding an army is one part of logistics, moving an army is the part I'm more concerned with. With a Zagros border, for a legion stationed in the north to assist a legion in the south it would have to march west all the way to Mesopotamia, take a boat down the Tigris, then then get out of that boat and march east meet up with (whatever remains of) the southern legion.* With a Tigris border they simply get in their boats and go right to the site of the incursion.

As far as I'm aware, there were roughly 7 legions on the border between Parthia and Rome. Lets assume the equivalent of 5 of them are relocated to Mesopotamia. Rather than have them find out they need to move, and then moving to any point along the Tigris, they have exactly 2 places they have to get to, and can set up river fortifications that can support them, allow rapid deployment and rapid disembarkment, with routes. Excluding any additional legions raised through Mesopotamian revenues, two Legions can be deployed to each of the major passes, without any risk to the cities, with three in reserve. That is an incredibly strong force, especially for relieving fortifications.

Meanwhile, with a river based approach, since there are fortifications in the mountains to delay them, Roman forces may only by able to respond once cities are almost under siege. A much more costly affair.
 
Feeding an army is one part of logistics, moving an army is the part I'm more concerned with. With a Zagros border, for a legion stationed in the north to assist a legion in the south it would have to march west all the way to Mesopotamia, take a boat down the Tigris, then then get out of that boat and march east meet up with (whatever remains of) the southern legion.* With a Tigris border they simply get in their boats and go right to the site of the incursion.

*they have go back to Mesopotamia because and army marching 1,500 km through a mountain range is logistically impossible even with modern technology.
But unlike a river,a mountain range is much easier to defend than a river.It’s going to be quite similar to defending northern China.Reinforcements will just have to march around Mesopotamia rather than across the mountain range.This is easily achievable considering Mesopotamia is a highly developed region with plains,roads,rivers etc,unlike the Carpathians.It’s far less difficult than marching legions from the Rhine/Danube to Italy or from the Rhine to the Danube vice versa like in the many civil wars.
 
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That conclusion is still not at all accurate. Any fortification that is in place in those passes will make advancing nearly impossible.
I wouldn't be so sure about that.

As long as you have a strong fort and a healthy reserve of supplies, and a way to ensure they can alert any deployed forces that they need relief. Even if it is just giant flaming beacons. More or less like any border fortification. An invading army that tries to ignore that fortification is in trouble.
The Sassanian army could overrun a border fortification pretty easily. To the best of my knowledge I don't recall the Sassanians ever struggling with OTL's border forts.

In addition, having forces on the river itself leaves those spaced out forces in danger.
How? They are in a position where they can get reinforcements very rapidly, they have a river and marshes hindering their enemy's movement, and they have a large number of fortified cities at their disposal.

Sure when the news gets out there can be forces deployed, but a rapid campaign could take out field armies piecemeal, and threaten Roman supply lines, leaving them in a precarious position whilst waiting for reinforcements.
Yes, the defending force would be besieged, same goes for your mountain forts unless they build a sequel to Hadrian's wall.

This is true, but it does limit how affordable they are - simply because of the more secure Mesopotamian cities (although I fear I've said as much before).
That was actually one of EmperorOfTheNorthSea's points, and my reply to that still is
"Khorramabad and Hamadan are also pretty near the mountainous frontier, and Taurus would be basically right beside the Armenian gap. I reiterate, the pre-mongol Iranian Plateau really should not be underestimated."

As far as I'm aware, there were roughly 7 legions on the border between Parthia and Rome. Lets assume the equivalent of 5 of them are relocated to Mesopotamia. Rather than have them find out they need to move, and then moving to any point along the Tigris, they have exactly 2 places they have to get to,
And Bushehr, and the Armenian Gap, which was something you brought up.

and can set up river fortifications that can support them, allow rapid deployment and rapid disembarkment, with routes.
So a not as good alternative to just using the Tigris?

Meanwhile, with a river based approach, since there are fortifications in the mountains to delay them, Roman forces may only by able to respond once cities are almost under siege. A much more costly affair.
Yet also in line with Roman defensive doctrine with regard to anything the border guards can't stop.

FYI, that just comes off as rude.
Yeah, sorry about that, I'm just a little exasperated with this thread.
 
But unlike a river,a mountain range is much easier to defend than a river.
Not necessarily. They form a choke point, but major trade routes run through the Zagros, they aren't hard to pass.

It’s going to be quite similar to defending northern China.
The place where they built a giant wall to improve the logistical situation and still couldn't stop the nomads? Not a strong case.

Reinforcements will just have to march around Mesopotamia rather than across the mountain range.
So we're still effectively moving the military frontier west to Mesopotamia?

This is easily achievable considering Mesopotamia is a highly developed region with plains,roads,rivers etc,unlike the Carpathians.
Also unlike the Zagros and their immediate surroundings. I mean they were developed to an extent (it's also not like the Romans sat on their hands for the century they owned Dacia, nor did they take it from unwashed barbarians) but no where near as developed as Mesopotamia.

It’s far less difficult than marching legions from the Rhine/Danube to Italy or from the Rhine to the Danube vice versa like in the many civil wars.
I'd think that it's a given that moving along one's border is easier than conducting a civil war.
 
Not necessarily. They form a choke point, but major trade routes run through the Zagros, they aren't hard to pass.
Which is why these locations can be well supplied and be marched to by friendly armies easily?As long it's a choke point,it's good enough to defend.Also,major trade routes doesn't mean it isn't defensible.Switzerland is also a major trade route.It's easily defensible.Often,a place is a major trade route precisely because it's defensible(narrow and people can only pass through that particular region to get to another place).

The place where they built a giant wall to improve the logistical situation and still couldn't stop the nomads? Not a strong case.
They fended off most of the nomad invasions.The wall isn't there to improve the logistical situation either.

So we're still effectively moving the military frontier west to Mesopotamia?
What? You are making no sense here.We are talking about the reinforcements march through Mesopotamia proper and then into the Zagros. Would armies from the Danube marching through Italy to in order to reinforce Britannia make all the territories in between a military frontier?


Also unlike the Zagros and their immediate surroundings. I mean they were developed to an extent (it's also not like the Romans sat on their hands for the century they owned Dacia, nor did they take it from unwashed barbarians) but no where near as developed as Mesopotamia.
You just debunked your own point. Read my first point for more information.

I'd think that it's a given that moving along one's border is easier than conducting a civil war.
There were frequently troop transfers all over the empire even when there's no civil war.
 
Which is why these locations can be well supplied and be marched to by friendly armies easily?
Not as easily as if they were on a river, and there's a difference between supplying and army in the mountains and supplying an army the has crossed over the mountains (the one that has crossed the mountains can resume foraging to supplement the logistical situation).

As long it's a choke point,it's good enough to defend.
Not all choke points are defensible, Thermopylae in 1941 being a good example of such.

Also,major trade routes doesn't mean it isn't defensible.Switzerland is also a major trade route.It's easily defensible.Often,a place is a major trade route precisely because it's defensible(narrow and people can only pass through that particular region to get to another place).
Could it be defended sure. However the fact that it is a trade route indicates that they are wide enough passes to facilitate a high volume of traffic, meaning that a very large fortress would be needed to actually close the pass to invaders.

They fended off most of the nomad invasions.The wall isn't there to improve the logistical situation either.
Objectively false, the wall literally does double duty as a road.

What? You are making no sense here.We are talking about the reinforcements march through Mesopotamia proper and then into the Zagros.
Thank you for completely ignoring what I told you two posts prior.
"With a Zagros border, for a legion stationed in the north to assist a legion in the south it would have to march west all the way to Mesopotamia, take a boat down the Tigris, then then get out of that boat and march east meet up with (whatever remains of) the southern legion."

Would armies from the Danube marching through Italy to in order to reinforce Britannia make all the territories in between a military frontier?
No, they would take the Danube river as far north as the could, then take a road that takes them to the Rhine river and take that to northern Gaul.

You just debunked your own point. Read my first point for more information.
No I didn't. There is basically no north-south infrastructure in the Zagros, it's 1,500 km through mountains and foot hills. The nearest major Persian road that run north-south west of the Zagros follows the Tigris. You're trying to say rome can run north-south logistical operations with infrastructure that almost exclusively runs east-west!

There were frequently troop transfers all over the empire even when there's no civil war.
Yes, and?

edit: honestly I think a big part of why you aren't understanding my arguments is that you're misunderstanding the point I'm trying to argue. I'm not saying that the Zagros wouldn't work as a frontier, I'm saying the Tigris is better.
 
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Not as easily as if they were on a river, and there's a difference between supplying and army in the mountains and supplying an army the has crossed over the mountains (the one that has crossed the mountains can resume foraging to supplement the logistical situation).


Not all choke points are defensible, Thermopylae in 1941 being a good example of such.
If the Persians had artillery,tanks and planes,I guess nothing in the Roman Empire's really defensible.

Could it be defended sure. However the fact that it is a trade route indicates that they are wide enough passes to facilitate a high volume of traffic, meaning that a very large fortress would be needed to actually close the pass to invaders.
Trade back in those days does not require massive trains or trucks.It's why a place as narrow as the Cilician Gates used to be a major trade route back then.

Objectively false, the wall literally does double duty as a road.
Plain wrong.To begin with,most sections of the wall's undefended.A lot of it's actually ridiculously narrow. In fact,large parts of the wall were even interconnected.Only a few key points like Shanhai Pass were actually garrisoned.


Thank you for completely ignoring what I told you two posts prior.
"With a Zagros border, for a legion stationed in the north to assist a legion in the south it would have to march west all the way to Mesopotamia, take a boat down the Tigris, then then get out of that boat and march east meet up with (whatever remains of) the southern legion."


No, they would take the Danube river as far north as the could, then take a road that takes them to the Rhine river and take that to northern Gaul.


No I didn't. There is basically no north-south infrastructure in the Zagros, it's 1,500 km through mountains and foot hills. The nearest major Persian road that run north-south west of the Zagros follows the Tigris. You're trying to say rome can run north-south logistical operations with infrastructure that almost exclusively runs east-west!


Yes, and?
All of what you said is not a problem at all. Armies in the classical period have traveled far longer distances without problems.You are not manning the entire Zagros,just the two points.These two points are linked by roads to Mesopotamia proper.If an attack that's big enough is able to overwhelm the legions defending one of the entrances before reinforcements can arrive,then that's a massive failure in military intelligence.Even if there really isn't any north-south infrastructure linking the Zagros to Mesopotamia,you think the Romans are just gonna squat the whole time during the occupation and do nothing about it despite their reputation as rather excellent road builders?

edit: honestly I think a big part of why you aren't understanding my arguments is that you're misunderstanding the point I'm trying to argue. I'm not saying that the Zagros wouldn't work as a frontier, I'm saying the Tigris is better.
No mate,I understand your argument.It's that your arguments are full of faults.The problem with Tigris as a border is that you cannot use Mesopotamia to it's fullest economically.It will be a perpetual warzone.
 
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One point that comes to mind is that while a river works nicely against Rome's less advanced opponents; it is no barrier at all to a peer power. In this case, Persia was one of only a handful of powers that even Rome considered to be their equals. Rome, or specifically Caesar was able to bridge the Rhine River in just a handful of days. The point being that an organized military power with an understanding of engineering is not going to have much of a problem crossing a river before the defender can respond.

There is also the whole point of wanting to take Mesopotamia in the first place. You want it's economy. If you have your border on the river you leave a huge portion of the region in enemy hands and thus get no money from them. You also face near constant raids as others have mentioned that potentially ruin the region economically. Again defeating the purpose of being in the region in the first place.
 
If the Persians had artillery,tanks and planes,I guess nothing in the Roman Empire's really defensible.
I was referring to the terrain, how due to erosion the famous choke point had widened to the point where it have required tens of thousands of men to properly defend it. I apologize for not being clearer.

Trade back in those days does not require massive trains or trucks.It's why a place as narrow as the Cilician Gates used to be a major trade route back then.
Fair enough. Too bad we don't have many Iranian members on the board who could clarify exactly how narrow or wide the passes are.

Plain wrong.To begin with,most sections of the wall's undefended.A lot of it's actually ridiculously narrow. In fact,large parts of the wall were even interconnected.Only a few key points like Shanhai Pass were actually garrisoned.
Thanks for debunking your own argument?

The problem with Tigris as a border is that you cannot use Mesopotamia to it's fullest economically.It will be a perpetual warzone.
the actual frequency of Roman-Persian wars OTL makes me severely doubt that.

No mate,I understand your argument.It's that your arguments are full of faults.
You keep making the same argument (that logistics can just be routed through Mesopotamia) then failing to understand that's an argument in favour of just moving the border back to Mesopotamia and cutting out a few days of marching and a few years of building roads through the foothills of a major mountain range.
But unlike a river,a mountain range is much easier to defend than a river.It’s going to be quite similar to defending northern China.Reinforcements will just have to march around Mesopotamia rather than across the mountain range.This is easily achievable considering Mesopotamia is a highly developed region with plains,roads,rivers etc,unlike the Carpathians.It’s far less difficult than marching legions from the Rhine/Danube to Italy or from the Rhine to the Danube vice versa like in the many civil wars.
What? You are making no sense here.We are talking about the reinforcements march through Mesopotamia proper and then into the Zagros.


You are not manning the entire Zagros,just the two points.These two points are linked by roads to Mesopotamia proper.
Have you read the first page of this thread? The area of Bushehr and the gap formed by the Armenian highlands would also need to be defended, and these regions don't have millennia of infrastructure built for them. That's 4 legions for the border, that same number could surely defend the shorter and more navigable Tigris with greater efficiency.

The problem with Tigris as a border is that you cannot use Mesopotamia to it's fullest economically.It will be a perpetual warzone.
You're actually the first to bring it up so you can't really blame me for not addressing it sooner. Anyways, a Tigris border wouldn't give the entirety of Mesopotamia, but it would give the lion's share of it (and awkwardly bisect Seleukia-Ctesiphon). And given the actual frequency of Roman-Persian wars IOTL I don't think perpetual devastation is on the menu, the two powers traded more than they warred .
(in a period of 697 years of contact, they spent around 120ish years at war with each other, which is alot but not devastating to a region, as it wasn't to Northern Mesopotamia and Syria IOTL).

One point that comes to mind is that while a river works nicely against Rome's less advanced opponents; it is no barrier at all to a peer power. In this case, Persia was one of only a handful of powers that even Rome considered to be their equals. Rome, or specifically Caesar was able to bridge the Rhine River in just a handful of days. The point being that an organized military power with an understanding of engineering is not going to have much of a problem crossing a river before the defender can respond.
Caesar was able to do that because the Germans weren't patrolling the river and didn't have a riverine navy that could block an enemy build up. I'd suggest looking at the first page of this thread where I addressed this exact point. As long as the Romans have naval superiority on the river it's a solid defence against just about everything.

There is also the whole point of wanting to take Mesopotamia in the first place. You want it's economy. If you have your border on the river you leave a huge portion of the region in enemy hands and thus get no money from them. You also face near constant raids as others have mentioned that potentially ruin the region economically. Again defeating the purpose of being in the region in the first place.
See above.
 
I was referring to the terrain, how due to erosion the famous choke point had widened to the point where it have required tens of thousands of men to properly defend it. I apologize for not being clearer.


Fair enough. Too bad we don't have many Iranian members on the board who could clarify exactly how narrow or wide the passes are.


Thanks for debunking your own argument?
No,you simply just have no idea about how northern China’s defended.A large part of what the Great Wall covers is inhospitable terrain,like mountains,deserts.In these parts,the area’s so inhospitable that apart from some raids,the enemy simply could not conduct any large scale assault through these areas.To conduct a large invasion however,the enemy will have to assault key locations like mountain passes that are definitely well defended.Most of the time,such attacks are repelled.In actuality,a number of dynasties like the Tang Dynasty didn’t even bother with the wall and simply just posted strong field armies that prefers to attack the enemy rather than be attacked.Whenever there is a problem,you don’t see armies from another part of the wall reinforcing a besieged section,rather you just get army units from other parts of the country further south marching to reinforce that area.The fact that the wall’s situated in an area not known to produce grain does not mean that the government could not support these troops.Grain from as far as south China was transported there.The Zagros is just next to one of the most productive agricultural fields on the planet.If the Chinese government can transport grain from Southern China on a timely manner to the north,the Romans can definitely transport grain from Mesopotamia to the Zagros.As you have mentioned,the two points are trade routes.This means they are well connected to Mesopotamia and beyond.

the actual frequency of Roman-Persian wars OTL makes me severely doubt that.


You keep making the same argument (that logistics can just be routed through Mesopotamia) then failing to understand that's an argument in favour of just moving the border back to Mesopotamia and cutting out a few days of marching and a few years of building roads through the foothills of a major mountain range.
I didn’t make the same argument.I went further and tore apart your claims of why making the Tigris River the border is feasible.




Have you read the first page of this thread? The area of Bushehr and the gap formed by the Armenian highlands would also need to be defended, and these regions don't have millennia of infrastructure built for them. That's 4 legions for the border, that same number could surely defend the shorter and more navigable Tigris with greater efficiency.


You're actually the first to bring it up so you can't really blame me for not addressing it sooner. Anyways, a Tigris border wouldn't give the entirety of Mesopotamia, but it would give the lion's share of it (and awkwardly bisect Seleukia-Ctesiphon). And given the actual frequency of Roman-Persian wars IOTL I don't think perpetual devastation is on the menu, the two powers traded more than they warred .
(in a period of 697 years of contact, they spent around 120ish years at war with each other, which is alot but not devastating to a region, as it wasn't to Northern Mesopotamia and Syria IOTL).


Caesar was able to do that because the Germans weren't patrolling the river and didn't have a riverine navy that could block an enemy build up. I'd suggest looking at the first page of this thread where I addressed this exact point. As long as the Romans have naval superiority on the river it's a solid defence against just about everything.


See above.
If the area doesn’t have a much infrastructure built for the defending army to march and garrison it,you think the same could be said about an attacking army?RogueTraderEnthusiast has already addressed your points on Bushehr.

Furthermore,the Romans can likely raise additional legions out of Mesopotamia.

Covering the lion’s share of Tigris is good enough to allow the army on the opposite side to wreck the hell out of what’s on the other side.

Most of the Roman-Persian wars were limited to northern Mesopotamia and the eastern parts of Syria as you mentioned,but these areas are far from being the richest areas of Syria and Mesopotamia.There’s a massive reason why the richest part of Roman Syria is in the west and why the richest part of Mesopotamia is in the south.As to the claim about these areas not being devastated by war,I very much doubt this claim.

As long as the Romans have naval superiority?What the Roman will face are not low tech barbarians,they will be facing Persians who definitely did field navies of their own,not to mention far more experienced in the Tigris than them.The Romans simply can not guarantee naval superiority against the Persians here.Even if you aren’t attacked,you are still leaving out the highly fertile eastern bank of the Tigris to the Persians.
 
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