In 1053, Pope Leo IX formed a coalition of Lombards and Byzantines against the Normans of southern Italy, who were at the time in the process of conquering Apulia. The Pope raised an army of Italians, Lombards, and Swabian Germans and lead it south from Rome, while a Byzantine army under Catapan Argyrus moved north from Apulia, with the intention of uniting with the Papal force. The Normans moved too quickly, however, and caught the Papal army at the town of Civitate (northwest of the city of Foggia, in Apulia), in June 1053, before the Papal forces could unite with the Byzantines. In the ensuing battle, the Normans, despite being outnumbered by two-to-one, were victorious. For more details of the battle and the background for it, see here.
Let's assume, however, that for some reason the Normans are delayed in their reaction, or the Byzantines move faster, and the Byzantine and Papal armies are united at the Battle of Civitate. They now have an overwhelming force and pretty much annihilate the Normans. Robert Guiscard and most of the other Norman leaders are killed, and only a few hundred of their men escape the slaughter.
So, what are the effects? I can see several.
1) No Norman Kingdom of Sicily. What ramifications from that? Possibly the Muslims remain in control there for a much longer period? Obviously Sicily does not pass to the Hohenstaufens in the next century...
2) A longer period of good relations between the Papacy and the Byzantine Emperor (Pope Leo IX had good relations with Emperor Constantine X Doucas which were pretty much broken after the Papal defeat at Civitate).
3) Possibly no Great Schism, at least not in 1054, as the Byzantines will return to rule of Apulia and Calabria, allowing the Greek Churches there to reopen and resume Greek practices (the Normans had been imposing Latin practices on the Greek churches in the area, which was the instigation which caused Patriarch Michael Celunarius to close the Latin churches in the East and set off the process which lead to the Schism).
Any other thoughts? Effects on the Crusades, for example?
Let's assume, however, that for some reason the Normans are delayed in their reaction, or the Byzantines move faster, and the Byzantine and Papal armies are united at the Battle of Civitate. They now have an overwhelming force and pretty much annihilate the Normans. Robert Guiscard and most of the other Norman leaders are killed, and only a few hundred of their men escape the slaughter.
So, what are the effects? I can see several.
1) No Norman Kingdom of Sicily. What ramifications from that? Possibly the Muslims remain in control there for a much longer period? Obviously Sicily does not pass to the Hohenstaufens in the next century...
2) A longer period of good relations between the Papacy and the Byzantine Emperor (Pope Leo IX had good relations with Emperor Constantine X Doucas which were pretty much broken after the Papal defeat at Civitate).
3) Possibly no Great Schism, at least not in 1054, as the Byzantines will return to rule of Apulia and Calabria, allowing the Greek Churches there to reopen and resume Greek practices (the Normans had been imposing Latin practices on the Greek churches in the area, which was the instigation which caused Patriarch Michael Celunarius to close the Latin churches in the East and set off the process which lead to the Schism).
Any other thoughts? Effects on the Crusades, for example?