From a reader I’ve long relied on for Islam stuff and who shall henceforth be known in this space as “my Islam guy.”

Jonah,
I could dig up more details for you, but off the top of my head, here’s the deal with “fedayeen” and the “devil worshippers” Rick Brookhiser mentioned earlier on the Corner.
1. “Devil-worshipping” Yazidis. Basically they’re a sect that has an interesting take of the “Fall of Lucifer” tale as it exists in Islam. In Islam, Iblis (Satan) fell because when God created Man, he ordered all the angels to bow down before him, since Man was His supreme creation. Iblis refused. For this, he was banished. The Yazidis consider his refusal to bow to have been, in fact, a correct and pious act, since one _never_ bows before a creation, only the Creator Himself. So they consider Iblis a “good” angel or saint. They’re not devil-worshippers in the western, Satanist sense (i.e., anti- the main religion).
2. “Fedayeen” comes originally, as far as I know, from the Nizari Isma’ili sect best known in the west as the Assassins (who were not, incidentally, hash-addled goofballs, but gnostic ascetics. The term “hashishin” seems to have been a pejorative stuck on them by their neighbors, perhaps like, “Those crackheads up in the fortress there.”) The assassins’ operatives, who were often what we’d call deep-cover agents, were called “fidâ’î” (singular) / “fidâ’iyûn.” The literal connotation is “sacrificer,” in the sense of one who’s willing to risk his life for a cause. It’s since become a general term for commandos, shock troops, etc. In the current context, your description of the “Fedayeen Saddam” as a Ba’athist brownshirts is perfectly correct.