In regards to the Abbasid Revolution, I was taught of a massacre performed on the remaining Umayyads (of which Abd al-Rahman survived). Is this information accurate? And, if so, who performed the massacre?

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Really, some serious Game of Thrones shit went down. So basically, in 749-750 the Umayyad caliphate based out of Damascus fell. As you know the Abbasids became the new rulers. They moved their capital to what is now Iraq and built Baghdad. Basically there was a bloody massacre of the Umayyad family when Abul 'Abbas as-Saffah captured Damascus, was proclaimed the new Caliph and held a feast to celebrate the new peace between them, inviting the remaining Umayyads and promising to give them pardons. While at the feast, they were all killed. It's not easy to find lengthy details about the feast, although one particular text I have cites an earlier source that says he invited eighty (!) members of the family to this feast, noting all of them were killed there.

Who did the killing, and how? I do have one text that says it was "hired assassins" or "mercenaries" wielding clubs, who came out during the feast and clubbed the Umayyads to death. It follows by stating that leathers were brought out by servants, who promptly covered up the dead bodies, cleaned up a bit, and then the feast resumed. Another source I have cites a very old text says that things went down a bit differently. In this version, it was simply as-Saffah's guards who did the killing. They came out and arrested the Umayyads, covered them with carpets, and then clubbed them to death right there in the feast hall. Whereupon the feast quickly resumed. Basically every source I have says that they were clubbed to death by men hired by as-Saffah, although there seems to be a bit of disagreement on whether they were hired killers, guards, or mercenaries. There also seems to be a bit of disagreement over whether they were killed before or after they were covered up with leather (or carpet). Most seem to say they were covered up afterwards though, which makes sense.

As for Abd al-Rahman I specifically ('Abd al-Rahman ibn Mu'awiya), the story of his escape and journey to al-Andalus is somewhat fantastic, although generally accepted. At least, I have yet to see someone challenge its veracity even with how extraordinary it seems. These things do happen though. I've got a book here where Maribel Fierro even says openly in the text that the story of Abd al-Rahman I's escape "would make an exciting script for a Hollywood movie" and honestly, I agree. He was around about 20-21 when he fled. He asked his loyal client Badr (a freed slave), to help him and some of his family flee and together they went from Syria to Northern Africa. Who specifically went with him I see slight variation in details, but generally he had at least one sister and his brother Yahiya with him, and probably a son and other sisters. They fled south, following the Euphrates river and many interesting things happened along the way. Abbasid troops - soldiers and horsemen - were were sent throughout the region to locate them. While stopping in a village, they were located and they split up - his son was left with his sister(s) in the village where they remained in hiding. Again, sources vary a bit here, but Badr either left the village with Abd al-Rahman and Yahiya, or he fled separately and met up with them later.

One of the most dramatic events that occurred was after they had escaped the Abbasid horsemen, who ended up catching them on the bank of the Euphrates. The three of them dived into the river to swim across, whereupon they were separated from Yahiya. At this point I see some varying descriptions - probably the influence of folklore or romanticisation from medieval historians. Either Yahiya swam back towards the shore where the Abbasid horsemen were because he was having trouble swimming and didn't want to drown, or he deliberately went back to shore to distract the horsemen to allow Abd al-Rahman and Badr to get away safely. The horsemen are reported to have promised the three that if they surrendered they would be permitted to return to the caliphate, and Abd al-Rahman is said to have virtually begged Yahiya to come back and swim out to him. Once Yahiya got to the shoreline, the horsemen approached and cut his head off, leaving the body at the river bank. The earliest sources I know of then say that at this point that Abd al-Rahman was so overtaken by fear at the sight of this that he ran until he couldn't breathe.

From there they went south through modern-day Palestine, into Egypt, and then west through northern africa. Travelling through Egypt was equally difficult because the governor, Ibn Habib, had troops and spies searching for Abd al-Rahman in an effort to pleasr the Abbasids. Note that our main man Abd al-Rahman I did have a specific reason for going where he did. Basically his mother was a Berber woman and he was looking for refuge in her tribe, the Nafza. However, he was found by Abbasid agents (troops sent by Abbasid commanders to find him when alerted by locals) while amongst the Berbers. It's reported that once, while in a camp of Berbers in northern Africa, to avoid Ibn Habib's troops the chieftain of the Berbers' wife hid Abd al-Rahman amongst her clothing. I'm not completely convinced this particular story with the hiding under the Berber chieftain's wife's clothes happened, but given the widely accepted nature of other event, I guess it's possible that it really did happen in some form. Worried that he might be discovered by the Abbasids again he ended up moving further west, whereupon he found former clients (tribal people who were sworn to the Umayyads) of the Umayyad caliphate settled in al-Andalus.

Which at the time was completely immersed in interna, conflicts between different factions of the army. These were mainly tribal divisions, pitting the Qaysi (northern) arabs against the Yemeni (southern). The Qaysi were led by a guy called al-Sumayl who actually commanded several governors in al-Andalus, and he was slowly moving towards victory over the Yemeni.

Abd al-Rahman's supporters tried to get al-Sumayl's help bringing Abd al-Rahman to Iberia. Al-Sumayl was against it though because he knew that the second Abd al-Rahman showed up, the tribal groups would probably lose their independence. Fierro quotes him as saying something which I've always found to be pretty hilarious, that Abd al-Rahman "belonged to a clan of such importtance that if any of its members urinated in the Iberian peninsula, all its ttribal leaders would be drowned." So basically al-Sumayl refused to help, meaning that the Umayyad clients immediately turned to the Yemenis. Then he crossed the Strait of Gibraltar in 755 and began his rule a year later.