OK, let's play... I have heard one argument that trying to enforce orthodoxy on the regional religious communities (Coptic, Nestorian, Monophysite, etc.) is what made them susceptible to Islamic rule in the first place. Islamic rulers didn't care what form of Christian infidels they ruled as long as they submitted peacably to taxation. One of the strengths of the Roman Empire was that it (by and large) accepted, tolerated and even encouraged whatever religions the locals had. The Byzantines could not do this.

True, the Christian revolution did fundamentally change Roman religious policy, and both the orthodox and Catholic factions were dogmatic in their intolerance (to varying degrees). Islam was by far more tolerant, and this showed in the rapid conversion of much of the conquered populations (well tolerance and tax concessions!). Nevertheless, religious dominance was nearly always a matter of military might. Turkey remained Christian as long as Byzantium was its master, and Syria, Egypt etc I expect would also have remained Christian if CHristian ruled. Ongoing rule of Italy from Constantinople may well have prevented the schism that split christianity centuries later, as the east would've worked hard to have 'friendly' popes in Rome. Issues would have been a continual problem for them though: Any war to fully reclaim the west would've been a tremendous drain on their resources, and would've left the East vulnerable on the Danube to Bulgars, Magyars, Pechenegs etc, and in the mideast with the Islamic nation of Persia. And of course, even a successful campaign in the west would've tempted generals to become Imperator of the West, and thus civil wars.

>>Nevertheless, religious dominance was nearly always a matter of military might.<< I might differ here. Religion reflects cultural and ethnic heritage as well. People choose religions partly to show who they are, and who they are not. The Coptic church in Egypt is an example of this. It had cultural roots and it endured despite Constantinople's military occupation. It seems to be concentrated in upper Eqypt now, lower Egypt has a much higher percantage of Muslims. >>Turkey remained Christian as long as Byzantium was its master<< Byzantium would not rule Muslim minorities. In the 3 centuries that it held its own against the Caliphate, the population of any reconquered territory was given the choice of conversion or emmigration. The early Ottomons had court officials whose job it was to protect "People of the Book" from unjust exactions by Muslims. This, along with the continual, bloody raids against Roman lands by Turkish ghazis broke the back of Constantinole's rule in Asia Minor. BTW, these offices were eliminated after Byzantium was conquered. Interestingly enough, Turkey had a large Christian minority until the Greeks and Armenians were forcibly driven out in the first 2 decades of the 20th century. I think it was 30-40 percent or higher. This continuing religious identifications was in the face of 4 centuries of harsh and officially sanctioned discrimination. Those who remained Christian did so because of their ethnic identification. Another thought is that The eastern Mediterranean was alwasy ore important to rome than the western mediterranean was to Constantinople. Rome HAD to hold the Hellenistic eastern mediterranean. It was the economic and intellectual mainspring of the Mediterranean world. Holding on to the west was not an economic necessity for Constantinople.

'In the 3 centuries that it held its own against the Caliphate, the population of any reconquered territory was given the choice of conversion or emmigration.' True, but that reinforces my point of religious dominance. If the Byzantines controlled the area, the area soon became christian. And whilst the Muslims were more accepting, once conquered by Arab or Turk, the population soon became predominantly muslim. True the turks did 'break the back' of byzantine rule in anatolia, but it was also the 4th 'crusade' that settled the issue. The Comneni emperors had been holding their own in the 12thC. In any event, Manzikert wouldn't have necessarily happened if the Romans had won at Yarmuk. That battle for me has always been the most decisive defeat for the Eastern Empire, more so than Manzikert (though the latter was also disastrous). Agreed, it was not an economic requirement, but it was an almost ideological drive. As the west had once been roman, there were many Byzantine emperors fixated on reconquering western provinces. That is why i felt a return to the west was likely. A secure eastern border in the 7thC would have allowed for the reconquest Italy from the Lombards. That does assume a secure eastern border though, which victory at yarmuk may not have guaranteed. It's interesting to wonder if even Persia would've fallen if the Muslims had suffered a decisive defeat so early on. I think yes, as the cream of their army had already been demolished.

I have greatly neglected study of the Roman Empire past the late 6thC/early 7thC, however, it is my opinion that by the mid-7thC, Byzantium could not have retaken the West. "Rome HAD to hold the Hellenistic eastern mediterranean. It was the economic and intellectual mainspring of the Mediterranean world." The reason that Byzantium and not Florence (I believe Florence was the new capital of the Western Empire by the 5thC) was the economic and intellectual center of Rome at the end of the Empire was because it was generally accepted that the West could no longer be held. The population of the West was decreasing. The military was disintigrating. There was little defence against the peoples coming from the northeast or even the old Celtic enemies. By giving up the West, the Roman Empire was given a chance to live through the Byzantine Empire. "Though anything is possible, I think it quite possible that the Romans (Byzantines) may have regained full control of Italy, and completely changed the future development of the Catholic church and Western Europe overall. Would Roman standards have flown over France, SPain and Britain once again?" "A secure eastern border in the 7thC would have allowed for the reconquest Italy from the Lombards." No matter how much the Eastern emperors wanted to conquer the "old empire," they would not have been able to do so and maintain control. The foundations of the Medieval alliances are already being laid in the west at this time, and all of them are sided with the pope. An attack "against the Church" by the Orthodox Christians would surely have driven the majority of peoples in the west to enter into the war. The west could not have provided enough resources (men, food, money, etc) to maintain the presence of the forces needed to hold this land against these forces, so the storerooms of the East would have been greatly depleted in the effort, weakening the East's ability to defend itself. If the Muslims had been defeated in 636, another force from Asia would surely have taken their place in war with Byzantium. Taking and maintaining the western portions of Europe would have been disasterous for the Eastern Empire, and the emperors must have realized that.

Yes but my suggestion is that if the Muslims had lost at Yarmuk the muslims would've continued east, focussing on Persia (which they were already grinding down) and then India. It would've been a long time b4 they chose to cross swords with the ROmans again. ranknfile, you are correct that retaking the west woulkd've depleted the east; Justinian's efforts proved just that. But with Persia destroyed and Islam focussed elsewhere, the eastern front would've been secure for some time. Apart from the Franks there were no serious military powers in western europe. I agree it is less liekly the East would've reclaimed Gaul, and no way Britain, but Italy i think yes, and Spain quite possibly due to the Eastern control of Sicily, Nth Africa, and the Balearic Is (good supply lines). IN thius period the Eastern Empire had the most efficient military mchine this side of China, and with capable generals the west was an easy target. The manpower deficiencies would've worked against the defending German tribes as much as the invading Romans. remember too the split btn Catholic and Orthodox was in its infancy, and a resurgent Empire would've soon dominated the Papacy. The SLavic migrations would've still split the empire in the balkans. The growing power of the franks is another factor, though who knows what impact a stronger Roman presence in the west may have had on them too...they were masters of intrigue.

By this time, hadn't the Pope already declared the Orthodox Christians heretics and excommunicated them? Spain and North Africa could probably have been taken if there wasn't the threat of renewed attacks by the Muslims in retaliation. The Germans also weren't troubled with the same population losses that the peoples inside the Western Roman Empire suffered. You also shouldn't underestimate the Norse invaders of the time. If the west is reunified, they have no choice but to invade the Roman Empire again in order to maintain their livlihood.

I don't think there was a formal split at this time; it was more a matter of doctrinal disputes. The papacy still considered the Eastern Emperor the Roman Emperor, and was supportive of anyone able to bring security to Italy. Thus we see collusion between Pope and Byzantines as late as 1040AD. However the Patriach at COnstantinople would've have had to accept Papal supremacy. The Emperor wouldn't have minded as long as the Pope accepted him as 13th Apostle. Would've also depended on the Eastern position on 'icons'. The East still had possession of Nth Africa at this time; Carthage was largely unaffected by the Persian War. German population losses were light because they weren't so big in the 1st place. Sure their limited trade meant limited exposure, but their societal status meant they could only field small armies. A Byzantine force under a veteran general would've trashed the Franks as easily as Belisarius crushed the Vandals and Ostrogoths. BUt as ever with these 'what ifs' once you start playing with one thread of history, everything else unravels around it. How would they have dealt with the Magyar threat? The Slavs? It's easy to say under good generals all goes well, but it only takes the rash action of one to undo decades of good work (Valens is one example). The various Nords may have limited success, due again to their small numbers, and Byzantine success against them in the 900s.

Edward Gibbon wrote about the Ethiopian invasion of Yemen (Arabia Felix?). They occupied Arabian territory during the reign of Justinian. They had invaded to come to the aid of Christians there. They were driven out apparently after the passing of about a generation in Arabia. Gibbon's "what if" of course was what if Justinian had used Byzantine power to expand Christian control beyond that established by the Ethiopians in Arabia and in so doing had confined Islam to the limited status of a local sect.

Before the Byzantines, the Phoenicians conducted trade by ship. For example their ships reportedly fetched tin from southwest Britain. And Phoenicians were sent on an expedition to circum-navigate Africa by Pharoah Necko. Carthage acquired power through trade. The Romans beginning with the reign of Augustus maintained trading stations in India and imported Chinese silk through India. During the decline of the Byzantines there were the Venetians who built power on trade. I wonder why the Byzantines didn't engage in more maritime commerce with western Europe, sub Saharan Africa, India and maybe even the Far East. And I wonder why they didn't follow that up with the building of military and political alliances to secure and maintain that commerce. Instead of the outright conquest of western Europe, a pursuit of interests in common many with feudal kingdoms or principlities may have led the Byzantines to at least greater power than they had if not domination of Europe.