Byzantine and Papal Reactions to an Early Muslim Sicily/Southern Italy

I have been working out the parts to a new Timeline regarding an early Muslim invasion of Sicily and I've run into a bit of a speed-bump. Assuming that this invasion occurs in 741, Which is when Constantine V ascends to the throne, what would be Byzantine reaction to an Arab capture of Sicily and subsequent invasion of Reggio and the rest of Byzantine Italy? Considering he was going to invade Caliph Hisham, what would he do against the Arabs? In addition, what reaction would the Papacy have? Considering the Arabs would be fighting against The Lombards, would they have been pleased at this development?

Furthermore, how would this affect the plans of Aistulf, the reigning(and aggressive) Lombard king? Considering that he had ambitions over the Papal state and Ravenna, would he put aside this to fight the Arabs or ignore the pleas of the Duke of Benevento? This may be the case as the current Duke at the ascension of Aistulf was not approved by him, but perhaps I'm wrong.
 
I suspect the pope would freak out. He is tied into the Byzantine system, so shares their perception of the arabs as an incredibly threatening foe. They will most likely call for assistance from the emperor because the Franks can do nothing for them, and the Lombards are too awful to contemplate. The Lombard kings are unlikely to view the threat as anything so major (largely because they are right in this assessment - cracking the Lombard kingdom is not going to be easy for an Arab invader). To the Byzanntine court this is going to be painful, but I don't think they'll be able to deploy the forces to stop it. The most likely thing is a sense of deja vu as the Arabs roll up yet another valuable province and nothing can be done about it.

However - how fast are the Arabs going to be able to advance across Sicily and into Italy? IOTL the conquest took a fair amount of time, and I don't think the Fatimids deployed fewer resources than the Umayyads could have, given the decentral organisation of their state. So, the advance will probably not be the lightning rush through a collapsing kingdom as per Hispania. If the Arabs spend a few decades reducing Sicxilian cities before they crposs the Straits of Messina, there will be two or three things to consider.

- they will have become a known diplomatic quantity. By this time, people will have made contact with them and found some accommodation.

- The South Italian principalities, especially Beneventum and Salerno, will have had time to prepare and they do not have the same inhibitions of aligning with the Lombard kingdom.

- The Arabs may simply run out of steam and settle into a pattern of piratical raiding across the sea. There is no rule that says the Umayyads have to be more successful than the Fatimids, especially since they would meet a Lombard kingdom more invested in the defense of Italy than the late Carolingians.
 
Depends partly on the speed of their advance. If the Arabs leisurely absorb Sicily over the course of several decades neither the Lombards nor the Byzantines will be overly concerned. The Pope may view them with displeasure, but will not do much because they are not a direct threat to his territories on the Italian mainland. The Lombards may even welcome them as a useful distraction, allowing them to operate more freely in northern Italy.

If the Arabs conquer Sicily in a lightning campaign the Pope will have a coronary and the Lombards and Byzantines will definitely be concerned; an Arab invasion of Italy proper will be very likely and could threaten them all. Probably some sort of alliance between the three will be formed and one or more expeditions to recover some of Sicily will be mounted, with who knows what outcome. The Arabs will definitely raid Italy and menace Italian and Byzantine shipping, and might even mount an invasion, but really lack the means to conquer Italy even in the best case.
 
The thing with the Ummayads vs the Fatimids is that the Fatimids were fairly invested in their wars elsewhere, and they were more centralized than the Umayyads. Decentralization can actually be a assistance in this case because of the fact that Damascus doesn't need to invest too many troops, as the general can simply levy the able men of the province. Like in Iberia, I would assume a successful campaign would make the Umayyad caliph decide to bring in reinforcements such as South Yemenis or the Syrian army. The main thing separating the Umayyads and the Fatimids is that for the Fatimids expanding Dar al-Islam was not nearly as important. To the Umayyads the Jizya and other Dhimmi taxes are a vital lifeline, not to mention that the Fatimids were more content on warring within Islam rather than against the Heathens(with the exception of Byzantium).

Considering that the invasion of Sicily consisted of around 10,000 men and the general who led it was a fairly seasoned one, I cannot see how, especially, in the atmosphere that the Byzantines are in (Namely Constantine's ascension causing problems) they cannot take Sicily fairly quickly. Likely areas will stay out of their control but considering the 740 expedition took Syracuse first Messina, Catania, and Palermo cannot really be much harder nuts to crack.

Really enjoy the responses, guys.
 

Vitruvius

Donor
This would probably be important for the development of Naples. OTL the Duchy of Naples was still a Byzantine dependency, controlling the coast from Gaeta to Calabria. It's Duke was typically appointed by the Byzantine governor of Sicily, so its connection to the Eastern Empire was via Sicily. Administration was still in Greek and the coins still bore the profile of the Emperor until Stefano II initiated the break with the East in 763 after which Naples became Latin and lost control of most of the other cities like Amalfi, Sorrento and Gaeta.

So if Sicily falls before that break Naples seems particularly vulnerable, both to the Lombards and the Arabs. I would assume an early move to Papal allegiance would be necessary for strategic reasons. Or would it be possible to start paying tribute to the Arabs while maintaining autonomy? I suppose the reactions of the Papacy, Byzantines and Lombards to the Arabs would dictate what happens here.

Longterm I was also thinking about the Emirate of Bari. OTL it was founded by some rogue saracen raider who conquered the city from the Lombards of Benevento and set up an Emirate. I suppose this reflects the nature of the Arab conquest of Sicily and the fragmentation of Arab power in the Mediterranean at the time. So assuming the Arabs hold Sicily after their initial conquest in the 8th century when the Caliphate fractures the Arabs already have Sicily as a springboard. So would we see more local conquest around southern Europe the likes of Bari or Fraxinet? Perhaps Arab/Saracen enclaves at places like Ancona, Amalfi, Gaeta, Civitavecchia, Pisa or La Spezia? Not a conquest of Italy but a serious intensification of slave raids and piracy which could cripple the development of Italy, especially the Maritime republics.
 
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