Subject: They were.
Author:
Posted on: 2014-08-05 15:21:00 UTC
Three of them, including the Witch-King, were lords of Numenorean descent (and there's a whole bunch of theorising about whether the Witch-King was a named character - or even a King of Numenor!); the second-in-command was named Khamul, and known as the Shadow of the East. Which, again, implies stealth and hidden manipulation.
Of the Rings, the Three are semi-tangential - they were handed out by Celebrimbor directly, not by Sauron. They also didn't go to the three kings of the Elves - Gil-Galad, Oropher of Mirkwood, and Amdir of Lorien - but to the High King of the Eldar (Gil-Galad again) and Galadriel, who at that point wasn't ruler of anything. Basically 'Brim had a thing for Noldor...
The Seven, though, were given to seven dwarf-lords, and we know that one of them went to the king in Durin's line. There were seven races of the dwarves, so it's entirely possible that Sauron gave a Ring to the seven kings of the dwarves. With that precedent, it's hard to imagine he would have given the Nine to some random blokes off the streets of Umbar.
You've drawn out the political side of things, and you're absolutely right: between them, the Nazgul run no less than four independent realms that we know of - Angmar, Dol Guldur, Minas Morgul, and (at certain times) Mordor itself. We can be reasonably sure they ran some of Sauron's eastern realms, too (fun exercise: see if you can spot the hidden workings of Sauron in the history of the earlier Third Age). For nearly six thousand years, the Nine were Sauron's lieutenants and political underlings. Despite the resemblance, they weren't Darth Vaders - they were Grand Moff Tarkins.
Only better with swords.
hS