At Muslims and Muhammad - the Impossible Task, I posted, "It is impossible that a man could behead 800 Jewish men who had lived in his city for centuries for the simple reason they refused to accept him as their leader, and be a prophet of God."
Few people realize that Medina in Saudi Arabia once had a majority Jewish population, just as Jerusalem and Tel Aviv do today. The National Museum of Saudi Arabia in Riyadh, which I've had the opportunity to visit and tours of which are often included in the itinerary of visiting Heads of State, does not even mention the word Jew in discussing the history of Medina before or after Muhammad's immigration there in 623 AD. In keeping with the Muslim practice of considering all pre-Islamic history as that of jahiliya or ignorance, hundreds of years of Jewish history in Medina were wiped out as completely as the history of 1500 years of Buddhism in Afghanistan. The Quran states in numerous verses including 3:85 that no other religion than Islam is accepted by Allah, and Muslim conquerors had no interest in preserving the cursed religious history and documentation of those they conquered.
The result of this is that only scattered historical fragments remain of the Jewish presence in Medina. The first Jews may have arrived in the area after the Babylonian emperor Nebuchadnezzar exiled the Jews from Jerusalem in 586 BC. Successive colonies probably arrived after the Roman Emperor Pompey's attack upon Judea in 64 BC, the conquest of Jerusalem by Titus in 70 AD, and again following Hadrian's persecution of the Jews 70 years later. They developed prosperous settlements in the area later known as Medina, and were skilled farmers, merchants, and gold smiths. Two of their three main tribes traced their ancestry back to Aaron, brother of Moses, and their Rabbis and sacred scriptures kept their Jewish identify alive. Muhammad's own grandfather, Abdel-Mutalib, was sent as a young boy to learn religion from the Rabbis, and Muhammad himself referred to them as People of the Book in distinguishing them from their illiterate and uneducated Arab neighbors. These Arab tribes began to arrive in the region from Yemen in the two centuries before Muhammad, and would often raid and attack the Jews. In response the Jews would claim that a Prophet was coming among them who would help them gain revenge against their enemies, and this is what caused the first Arabs from Medina to become Muslims.
Islamic historian Ibn Ishaq describes it as follows: At the annual fair at Aqaba outside of Mecca, the Prophet met a number of the Khazraj tribe from Medina. They lived side by side with the Jews, who were people of the Scriptures and knowledge, while they themselves were polytheists and idolaters. They had often raided the Jews in their districts, and whenever bad feeling arose the Jews would tell them that a Prophet was coming and that when he came he would kill them all. When they heard Muhammad's message, the Khazraj said, "This is the prophet of whom the Jews warned us! Let's get to him before they do!" They then accepted his teaching and became Muslims.
Soon after, these same people invited Muhammad to come to Medina. He did so with the expectation that the Jews there would also accept him as a Prophet. When they did not he expelled the first two tribes and then beheaded 600-900 men of the final tribe in one day. The only males who escaped were young boys who showed no evidence of pubic hair. The Jewish women, children, and property were divided among the Muslims with Muhammad himself taking twenty percent.
At this link, I have described in more detail the politically-motivated conversion of the first converts from Medina. At Muhammad and the Jews, Parts One, Two, and Three, I have described in more detail Muhammad's dealings with the Jews in Medina. Muslims go to great lengths to justify this treatment, but the simple fact is they were exiled and slaughtered simply for refusing to accept him as a Prophet.
At this link is a very graphic video of a Muslim beheading a man in the name of Allah. It is amazing to me that any Muslim could watch this video, and then imagine Muhammad and his companions repeating this slaughter 900 times and throwing the heads of their victims into the trenches they had dug for them, and still revere Muhammad is a prophet of God. I cannot. I cannot believe that a man who would treat the Jews of Medina as Muhammad did for not accepting him as a Prophet could possibly be a Prophet from God.