I only recently discovered how much later Islam originated than Christianity. The Council of Nicea was centuries before Islam came about. Jesus is mentioned in the Quran as an important prophet, and it seems plausible that a whole bunch of people inhabiting around the Mediterranean, could have spread Jesus' story to everybody in nearby places (modern day Spain, Algeria, Rome/Italy, into Turkey and Syria, Iraq, Egypt, etc.), and then Mohammad had a revelation which people paid attention to, also, in those countries, laying the foundations for this new religion. It sounds like the Jesus narrative gets to inhabit two religions at once, but it might be more like two competing narratives. So the Quran might have been written by people who read the Bible, by Christians themselves who now believe in Mohammed, and/or by people who had heard about Jesus' story in the past 600 ish years.
But how did the formation of another religion in the year 600-ish influence religion in Rome at the time? Were there formal opinions given by the Church? By that time Christianity is a half century old, formalized by the Roman Emperor in the 300s, and had been spreading since the events themselves happened via the Bible, but since some might have been illiterate, presumably by word of mouth as well.
I'm only now starting to learn about the wars between the Byzantine Empire and Muslim countries. Were they religiously motivated? I'm curious because of the connections between Islam and Christianity. Thank you
I just want to alert you to the premise of your question - Islam would be extremely old news to Christians in Italy in the year 700.
By the year 700, there had been armed conflict between Christians and Muslims for quite some time. The Byzantines and Muslims clashed in 629. Iberia was formally invaded in 711, but there had been conflict along the north coast of Africa for a good bit - as well as piracy. In 732, in fact, the Muslim invasion of Europe (if that was indeed the goal, which was questionable) reached its high-water mark in the West at Tours.
Dan Jones' new Thrones and Powers devotes quite a bit of time to the initial interactions between the Christian powers and the rising tide of Islam.
As far as religion itself went - From the Teaching of Jacob, set in 634 (and written by 640)
"And when I went out into Sykamina I communicated it to a certain very scriptural old man and I said to him: 'What do you say to me about this prophet who is appearing with the Saracens?' And with a great groan he said: 'He is a deceiver. Do prophets come with swords and chariots? Really these are works of disorder set in motion today, and I fear that the Christ who came earlier, whom the Christians worship, was the one sent by God and instead of him we shall accept Hermolaos. For Isaiah said that we Jews have a mistaken and hardened heart, until all the land is made a desert. But go forth, [211] Mr. Abraham, and learn about this prophet who is appearing.' And I, Abraham, thoroughly investigating, heard from those who met him that you find nothing true in this so-called prophet, except shedding human blood. For he says that he has keys of Paradise which is unbelievable."
http://andrewjacobs.org/translations/doctrina.html - Full Teaching
https://www.cambridge.org/core/journals/byzantine-and-modern-greek-studies/article/abs/sebeos-account-of-an-arab-attack-on-constantinople-in-654/B067CB79A2ADF5B9A47165D72E00737D - Another early account from a church figure (Sebeos) concerning Christian/Muslim conflict
https://erevangala500.com/upload/pdf/1323119797.pdf - and a more accessible bit on Sebeos