Roman defense in depth vs the Muslim invasions: a success?

[Kitsunegari]

I've been reading Walter Kaegi's book about this era recently, and one of the things that he emphasizes is the Roman predilection for relying on defensive strong points and only committing to battle when suitable terrain can be occupied, this in stark contrast to the Arabs' lightning campaigns and mobility.
p 59

A broad strategy of mobile defense in depth characterized Byzantine military operations and defense efforts in Palestine and Syria. This resulted from the small-scale frequent nomadic raids that did not normally require the mustering and dispatch of large intervention forces for the defense of the empire. The empire lacked the proper topography or sufficient manpower to resort to a frontal/forward defense strategy, which would have committed the bulk of troops along the empire's periphery to stop hostile incursions before they resulted in serious damage to the terrain, structures, agriculture, and civilian population of the exposed areas.

So in some ways this seems comparable to Constantine's reforms and it is understandable given the demographic decline and desperate financial situation after plague and constant war of the past century. The Romans best field army was far away from the action in the area of Constantinople and there were not large enough forces along the Palestinian and Syrian frontier to counter a serious invasion. This strategy also contrasts with the Persians' reaction to the Muslim attacks: mustering large (but often ill-prepared) armies for immediate retaliation. As in Alexander the Great's campaigns the Persians did not have a well-developed network of static defenses and so they were pretty much doomed after major defeats in the field; all this in spite of the Persians employing slow developing, caustious tactics in battle like the Romans.
p 60-61

Fortresses provided fixed points for defense... but Byzantine fortresses were not located in some manner that interlocked them so that no one could take or neutralize them except sequentially one by one. Only modest numbers of light forces, in the hundreds of troops, were stationed at scattered posts in a frontier zone of considerable depth (100+ miles probably) itself.
The Byzantines were prepared in Syria and Palestine to confront small scale penetrations by having mobile garrisons of local troops under duces, but local Arab allies did most of the patrolling and fighting. The central intervention forces who were best able to counter rare, large scale penetrations were located near Constantinople and behind upper Mesopotamian frontiers with Persia...
Muslim strategy and operations were well suited for this defense-in-depth of the Byzantines and took good advantage of it.

The fairly small forces available in Palestine, Egypt, and Syria were also of poor quality and could delay such a dangerous enemy at best. Also the Christian Arabs were often unreliable, even defecting to the Muslims at times.
conclusion

This strategy of defense-in-depth, because it avoided decisive tests whenever possible, probably, although at great civilian and territorial costs, contributed to the survival of at least one part of the Byzantine Empire.

Basically the Romans were trading land (very valuable land at that) for time to regroup and not risking decisive engagements, the exception was Yarmuk and there weren't many after that. So, considering the state of the empire and its military at the beginning of the conflict on one hand and the fate of its former rival Persia against the same enemy, is it justified to actually consider the Roman defensive strategy a success instead of utter failure (as it usually is), since it preserved the imperial core are in the long term and allowed for recovery and even reconquest in the future?

[6644kp]

But they never really recovered.


Byzantine Empire at the zenith of its territorial extent.


The Empire at its best point after the Arab invasion in 1180.

[Kitsunegari]

That's actually about over 100 years after their height under Basil II in 1025. But what i'm saying is that they remained a significant power and were in a position to regain even more ground if they had some strong emperors after Basil. OTOH many other states just collapsed under similar circumstances.

Spoiler Alert, click show to read: 

[DarthLazy]

It did work for them in the end and I believe their real deathblow was the 4th Crusade, but I do not really think the aim was to avoid giving battle.

Battle of Yarmouk
Battle of Krasos
Battle of Firaz
Battle of Bosra
Battle of Ajnadayn
Battle of Fahl
Battle of Maraj-al-Debaj
Battle of Hazir
Battle of Heliopolis
Battle of Nikiou
Battle of Carthage (698)
Battle of Iron Bridge
Battle of Sebastopolis
Battle of Anzen
Sack of Amorium
Battle of Mauropotamos
Sack of Thessalonica (904)

While they won ...

ROMAN
Siege of Constantinople (674–678)
Siege of Constantinople (717–718)
Siege of Nicaea (727)
Battle of Akroinon
Sack of Damietta (853)
Battle of Lalakaon
And a successful invasion of Syria .

So yea it did work .

[Tureuki]

Spoiler Alert, click show to read: 

Zangid sultanate, Seljuks in the eastern anatolia, what kind of map is that ?

[Manuel I Komnenos]

But they never really recovered.

...

You just skipped some 500 years and especially, the reigns of Nikephoros Phokas, John I Tzimiskes and Basil II whose deeds you should examine if you want to see to what extend did Byzantium recover. Not only did these Emperors halt the Arabian advance, they also undertook (especially Phokas and Tzimiskes) campaigns which recovered Crete, Asia Minor up to Georgia and a large portion of the Middle East, including cities like Edessa and Antioch, with a campaign of John Tzimiskes rumored to have reached Jerusalem.

[diez]

But they never really recovered.


Byzantine Empire at the zenith of its territorial extent.


The Empire at its best point after the Arab invasion in 1180.

Maybe in terms of territorial power not,but look at the empire during the Emperors mentioned above.
During Justinians reign,as well as other emperors of this era the empire had huge expenses to sustain all these armies and especially in the east there were always raids and defensive war making the populations life harder.During the Macedonian Dynasty though,especially during Tzimisces and Basi'ls reign there might not be as large as Justinian though,even people living at the borders were safe thanks to the Thema system,as well as the economy was much better,particulary,again thanks to the Thematic armies combined with other factors.

[6644kp]

I overlooked Basil II's reign. That was their height after the Arab invasion.

[Kitsunegari]

In the Komnenian era (most of 12th century) they were really strong as well, just didn't totally recover central Anatolia or southern Italy and they started to become more dependent on Italian merchants.

[Xanthippus of Sparta]

"Defense in depth" was indeed the overall strategy; but the details...tactics, organization, etc. of this style of warfare changed quite a bit throughout Byzantine history.

Up until the 7th century, the Byzantines used the traditional late Roman-style army made up of the limitanei garrison troops and comitatenses rapid reaction forces. Still a infantry-based army not unlike the forces of say, Theodosius.

This system was broken by the Arab invasions. The east Romans had a hard time dealing with the mobility of the Arabs. These forces were of course the pre-Turkic type based around infantry and foot archers, the difference being (from the Romans) is that they were mounted for travel.

After this, the Thematic system came into being. The tourmai, drouggoi, and banda, roughly equal to divisons, brigades, and regiments. The tourmai and banda were associated with a province; the tourmai to a large fortress and the command structure...the banda to a provincial region where they were recruited from. The drouggoi brigades resembled the comitatenses, in that they were the empire's mobile field forces. Also included the kleisourarachiai, frontier forces designed to contain and harass enemy raids into Roman territory. The early Thematic system stressed cavalry tactics, but large heavy infantry formations were to make a re-appearance from the 950s onward.

Thematic organization was pretty successful, the Byzantine resurgence took place while the Thematic system existed and probably partially due to it. Byzantine successes of the era aganist the Bulgars, and the Emirates of Chandax and Aleppo were fought under it.

But, this system could not last forever. John Haldon blames the high cost of maintaining it. Lars Brownworth blames the political situation, with the rich nobles buying up all the land and keeping it, tax free, while the Thematic system crumbled in response. John Julius Norwich is a little in between.

What came out is the reliance on a smaller, professional force, made up of east Romans and mercenaries from many different origins. Well led, as under the Kommenians, it was tough. Poorly led, like under the Doukai and Angeloi, it was a disaster.

[Kitsunegari]

I have Haldon's Byzantine Wars book as well, maybe i'll get around to reading it soon.
From Kaegi about the Muslim strategy that was so successful:

From the start of the Muslim invasions it was reportedly the strategy of Caliph Abu Bakr to engage in actions that would compel the Byzantines to send large numbers of troops to Syria so that the Muslims could defeat them in battle there. In other words, the Muslims, in contrast to the Byzantines, sought decisive victory on the battlefield.

They correctly decided that a big battle would play to their advantages of cohesion, mobility, and great officers.

[muller227]

Defense in depth strategies work well enough in theory when a state like the Byzantines are facing only armies, which is why they were able to recover from the early stages of the Islamic invasions. Mass migratory invasions like what took place in the 11th century however forever altered the ability to recover. The defensive depth is lost permanently too a new population. I think a misunderstanding of what they were actually facing in the late 11th century shot the system too hell.

In this vein also the attempt by Emperors at the behest of the Orthodox church to enforce a single version of Christianity onto a wide variety of Ethnic groups like the Armenians or the largely Nestorin population in Northern Syria created a populace in eastern regions that was constantly in flux relative to the Empire. These groups were not at all in some cases sad to see the demise of Byzantine authority. Nestorian Christians, played a vital role in the administrtion of the early Islamic conquests. Islamic rulers used this disaffection with Constantinople too their great advantage.

The Orthodox church for whatever reason never viewed the struggle with Islam as a fight too the death either until it was too late. Soldiers who had killed in battle were denied communion for a set period of time for example, the church always demanded payment of loans sometimes at the worst possible times. the disbandment of the Imperial regiments stationed in the eastern fortresses in the 11th century was largely brought on by the need too find cash, too both pay the church and the rather idiotic bureacratic nobility that had risen in power at the capital. The general population while unruly was not overly martial in inclination.

The sheer complexity of the byzantine state is hard too imagine. Runciman has a statement concerning Alexius taking the purple along the lines that only a brave genius or fool would have taken that responsibility. Whatever else can be said the reigns of Alexius and John probably extended Byzantine history for another 300 years. John Comnenus is terribly underrated as an Emperor, while Manuel his son seems overrated too me. John never lost a major battle, I am not even sure if he lost a minor one, and wherever he went local rulers bowed too his will. Including the the Proud lords of the Outremer, and the Rulers of the Islamic city states of Northern Syria.

Manuel had too huge F'ups, Myrocephalium his generalship was poor by most accounts and upset the delicate balance on the Anatolian frontier, and he married a Latin which through the succesion into chaos. Without these screwups the 4th Crusade would not have been dared. For the first simply scout the damned pass, for the second a perfectly good heirs were available for co-emperorship threw both Annes and Theodora's line. Andronicus was not trusted by anyone and slightly mad.

[diez]

Well,Manuel may not have been a Emperor-Warrior like Basil,Tzimisces who were extremely good at military tactics,battles etc.But he was an Emperor-Diplomat.He many times allied or sign truces with Indepedent Lords like the ones in Northen-Central Balkans,or Northern Syria,Eastern Asia minor,as well as with the West etc.This way he could have 1 sided wars,were still,the Byzantine Army was not the best as it was once but it was pretty capable.

After him this system of diplomatic relation,collapsed...

[Manuel I Komnenos]

Well,Manuel may not have been a Emperor-Warrior like Basil,Tzimisces who were extremely good at military tactics,battles etc.But he was an Emperor-Diplomat.He many times allied or sign truces with Indepedent Lords like the ones in Northen-Central Balkans,or Northern Syria,Eastern Asia minor,as well as with the West etc.This way he could have 1 sided wars,were still,the Byzantine Army was not the best as it was once but it was pretty capable.

After him this system of diplomatic relation,collapsed...

On the contrary, before Myriokephalon, Manuel was quite successful in the military field. He recaptured Kerkyra from the Normans in the campaign of 1147-49, invaded Apulia where his generals had some limited successes and achieved a complete victory against the strong Hungarians in Semlin (1167), which allowed him to expand Byzantine control over Serbia and Croatia.

As for the diplomatic field, Manuel tried to rally the Franks of the Outremer and sent a large fleet against Egypt, which failed to produce much success due to the fact that the Byzantines and the Crusaders couldn't cooperate effectively. Towards Venice, Manuel tried to gain the city's fleet support against the Normans, which helped him to retake the important island of Kerkyra. Later, he made a disastrous decision when he tried to undo the harm caused in the Byzantine trade interests, due to the fact that the Venetians had received plenty of rights in return for the services of their fleet. The Venetians were expelled from Constantinople and their property confiscated. Starting with this pretext, followed by the attacks of the mob against the Pisan and Genoan merchants in the days of Andronikos Komnenos which resulted in thousands of deaths, the Venetians decided to derail the 4th Crusade against Constantinople and be done with the Byzantine problem.

[Sher Khan]

Basically the Romans were trading land (very valuable land at that) for time to regroup and not risking decisive engagements, the exception was Yarmuk and there weren't many after that. So, considering the state of the empire and its military at the beginning of the conflict on one hand and the fate of its former rival Persia against the same enemy, is it justified to actually consider the Roman defensive strategy a success instead of utter failure (as it usually is), since it preserved the imperial core are in the long term and allowed for recovery and even reconquest in the future?

The trouble with this idea is that the Roman defense of Syria, Egypt, and the Jazira and Armenia did fail catastrophically. Yarmouk was not an exception so much as the next step in a defense-in-depth strategy. The Romans had allowed the Arabs to move around besieging here and there, retreating from Damascus to Emessa to Antioch and giving ground, until they could prepare their army for the next year. Yarmouk was the climax of a Byzantine counterattack that was successful up until the moment they lost in the field.

What saved Anatolia during the Rashidun expansion however was the reluctance of Umar and Uthman to advance into Anatolia and the reluctance of the Romans to counterattack by land. The first two caliphs were mainly concerned with establishing themselves and the hegemony of the local Arab tribes in Syria and Iraq and not so concerned with advancing into either Iran or Anatolia. However, Yazdgird bet everything on a land engagement and suffered for it with the collapse of his empire which had already begun to fracture into its smaller units. He had hoped a few years of raiding would weaken the Arab presence in Iraq.

What saved the Byzantines though was their decision - and the response of the caliphate - to change the battlefield from Cilicia to the Mediterranean seas. Led by Muawiyah the future Ummayad caliph and Ibn Saad, Uthman's appointment to Egypt, the Rashidun caliphate sought to engage the Byzantines at the sea when Heraclius managed to temporarily retake Alexandria through a naval invasion. From then on the focus was maintaining the Anatolian-Syrian front as a military march (with various Armenian client states changing loyalties every so often) while the Rashidun navy fought against the Greeks at sea, targeting important ports and islands. It wasn't until the Ummayad and Abbasid Caliphs that Anatolia and Syria both became perfect 'defense-in-depth' countries that only allowed each side to raid each other without any permanent change. In this regard it was a success, but in Syria it had been a resounding failure.

[Blatta Optima Maxima]

I don't think getting one's ass kicked can be called "defense in depth". Sorry, you can't put a spin on everything.

[motiv-8]

Basically the Romans were trading land (very valuable land at that) for time to regroup and not risking decisive engagements, the exception was Yarmuk and there weren't many after that. So, considering the state of the empire and its military at the beginning of the conflict on one hand and the fate of its former rival Persia against the same enemy, is it justified to actually consider the Roman defensive strategy a success instead of utter failure (as it usually is), since it preserved the imperial core are in the long term and allowed for recovery and even reconquest in the future?

Well, yeah, I guess, but only if you define 'success' by its strictest possible connotation: mere survival. And then the empire only barely succeeded. If you look at Byzantium at the height of Muslim power it looks strikingly like what Greece did in 1920, hanging on by a thread. A different turnout on one day in 717 or 718 and it all would have been gone.

If you define success as retaining its most wealthy, valuable, and populous territories which had been part of the empire for centuries longer than Constantinople existed then no, it wasn't terribly successful.

Not having read the book you reference I can't really say comment with authority, but I don't really see a huge pre-planned strategy of avoiding decisive battle on the part of the Romans. In the beginning they just didn't take the Muslim advance seriously, taking it as little different than the earlier border skirmishes and tribal warfare that was not uncommon in Arab and especially Bedouin lands. And then after some early skirmishes and small defeats they gathered an army with the express purpose of engaging the Muslims in the field, and were beaten. After that they avoided pitched battle for the most part, but the damage had already been done, at least in Syria and Palestine. Now, I think perhaps Heraclius withdrew the remainder of his army and some of the civilian population in order to preserve it yes, but for what? Could he have been planning an offensive campaign against the Arabs' rear just as he had done with brilliance against the Persians only a short time before? He died before any real plan could come about.

And then when the Arabs reached Egypt they didn't seem to pursue either a strategy of depth nor one of pitched battles. They mostly remained in the cities and counted on their ability to withstand Arab sieges, which the Arabs overcame with the initiative and stubbornness that was typical of them during those early campaigns. A defection by one really pissed off and corrupt Patriarch of Alexandria later, and there went the province.

Does this guy perhaps try to argue that the thematic system was a defense-in-depth technique? Like I said, I haven't read the book, but from what I have read I'm just not seeing it. The Empire was fighting for its very survival for quite a while, I just can't read much of a grand strategy into that, at least not at the time. Sher Khan on the other hand appears to recognize it (and assesses its failure), so I'm probably missing some pieces. There definitely have been books on Byzantine military and political strategy though. I haven't gotten around to John Haldon's book, has anybody else?

[Kitsunegari]

I guess i should qualify: by success i mean that i believe the only alternative to their (diminished) survival which allowed for later resurgence was total destruction, which befell Persia. The lack of money and experienced soldiers, geography, the superior cohesion and great commanders on the Muslim side, the unreliability (or even disloyalty at times) of their Arab allies who were depended on, and the fact that Roman control had only very recently been reestablished. By defense in depth i mean the organization which had been in place (with significant alterations) since Constantine I, not some strategy that Heraclius had devised specifically at this time since he was too busy restoring his authority in Palestine and showcasing prestige of returning the True Cross.

[Blatta Optima Maxima]

I really doubt it was an intentional long term plan.

[Timoleon of Korinthos]

I guess i should qualify: by success i mean that i believe the only alternative to their (diminished) survival which allowed for later resurgence was total destruction, which befell Persia. The lack of money and experienced soldiers, geography, the superior cohesion and great commanders on the Muslim side, the unreliability (or even disloyalty at times) of their Arab allies who were depended on, and the fact that Roman control had only very recently been reestablished. By defense in depth i mean the organization which had been in place (with significant alterations) since Constantine I, not some strategy that Heraclius had devised specifically at this time since he was too busy restoring his authority in Palestine and showcasing prestige of returning the True Cross.

But the reforms of Constantine and Diocletian were more primarily on the threats of Rhine and Danube and for this reason they mostly affected the provinces Gaul, Pannonia, Illyricum and Thrace. In Mesopotamia and Lazica, the traditional battlegrounds with the Sassanids a succession of eastern emperors (such as Anastasius, Justinian) envisaged a similar strategy therefore creating a network of fortifications, where the field armies could muster for an upcoming battle, retreat in the event of defeat and which could also be used as launchpads for raids and counter-invasions in Sassanid territories and whose garrisons could threaten Sassanian lines of communication during their incursions. But, as other posters have noted, in Syria and Palestine no cohesive strategy had been formulated, because no serious threat was expected from the deserts and the Ghassanids did most of the patrolling and fighting with the similarly occupied Lakhmids. In Egypt the strong fortifications of Pelusium and the annual inundation guarded the entrance into an otherwise lightly defened Nile valley. This absence of defensive depth became clear in the cases of the invasion of Khoshrau I and the campaigns of conquest of Shahrvaraz.

That having been said, in my opinion there has to be drawn a sharp distinctive line between the strategy of the (eastern) Romans before and after the initial phase of Muslim advance; the year 642 marking the conquest of Egypt can serve as a convenient albeit arbitrary turning point (although the exarch of Africa was similarly killed in a battle by Sbeitla in 647, but he was in open revolt at the time). Before that the Roman armies carried still the old Greco-Roman tradition that revolved around decisive pitched battles. Raids might be tolerated and cities might be left to fend for themselves against a siege, but that was only a temporary necessity until an army could be raised or transferred from somewhere else to seek a direct engagement with the enemy. In the early stages of Islamic expansion the Romans remained true to this mindset. When they first got sight of the enemy, Patrician Sergius, the senior officer in Palestine marched against them. He was defeated and killed by Gaza in 633. When word of this defeat reached Herakleios, he sent his brother Theodoros with reinforcements, who was also defeated by Abu Bakr at Adiabene. Then Vahan was sent against the invaders with fresh troops from northeast, who was defeated in two minor battles in 635 by Khalid. In the following year the field armies of the Orient and Armenia were combined under the leadership of Vahan and, augmented by the Ghassanids of Jabalah, attempted to re-establish imperial control and kick the Muslims out of Syria and Palestine for good, but they were destroyed at the battle of Yarmuk. Eventually the Romans run out of troops or capital to raise more or both. It's not because they were burning territories that they were forced to evacuate the Levant and whenever the Arabs made advances, it was after they had overcome the Romans blocking their way. During the invasion of Egypt the Romans may have rarely ventured beyond their walls, so it was mostly a matter of sieges (Pelusium in 640, Babylon, Nikiu in 646), but this was owed to the qualitative and quantitative inadequacy of their forces there, especially after their crushing defeat in the battle by Heliopolis, and the absence of prospects for further reinforcements from Constantinople.

After the consecutive defeats at the hands of the Arabs, which necessitated the Roman withrdawal to the line defined by the mountain ranges of Taurus and Antitaurus, the Romans came to the realisation that they should avoid pitched against the Arabs at all costs. The topography of the new frontiers, since the cavalry-based army of the Arabs was ill-suited for the rugged and mountainous central Anatolian plateu, and the change in the nature of the offensive warfare of the Arabs no doubt influenced this development. The Arab land offensive was de facto forced to shift towards raiding and pillaging as permanent occupation of Anatolia was difficult and the primacy was accorded to the naval arm the Caliphs were preparing for an assault on Constantinople itself, a much more feasible operation after the destruction of the Roman fleet in 655 in the Aegean. Thus the Romans devised a defensive strategy, whereby their armies would not offer battle, deliberately sacrificing land -not out of necessity because they were buying time, but because they feared the idea of battle alltogether. Instead they would either counter-raid the home territories of the invaders in an attempt to force them back or find the terrain that would facilitate an ambush. I believe that only this new strategy can be appropriately called "defense in depth" (one of whose tangible results was indeed that Cilicia was turned into a warzone and Anatolia was penetrated on numerous occasions) or at any rate it should be recognised as something radically different from its predecessor.