"Saracens." That is, Muslims. The period between the 8th and 9th centuries was characterized by waves of attacks on Europe by members of Mohammed's new delusional death cult, mostly Arabs from North Africa (although the ruling dynasties after the attacks were what would now be called Iraqis and Syrians). Spain fell, mostly because it was divided into tiny warring kingdoms - and didn't have anybody like John VIII!
“There is a lot of really old stuff under the ground”...ping
The Saracens never actually invaded Italy as they had Sicily. The sack of Rome was a raid and they never actually got inside the city walls. They did, however, look Old St. Peters.