Who were the Nazgul?

[CSteefel]

Originally Posted by Mansun

Sauron may have thought of the Balrog as the equivalent of Shelob in Cirith Ungol, as a guardian of a domain that belonged to Mordor but nevertheless a co-existance was inadvertantly made, since it prevented the enemy from seizing it.

The difference that I can see is that Shelob is the offspring of Ungoliant, who initially was allied with Melkor, but then went her own way. So Shelob seems to have a similar status. The Balrog were lieutenants of Melkor in the a same sense that Sauron was, even if their role was more exclusively for battle. OK, Melkor is gone, but I don't see any reason why the Balrog would be rivals or enemies. But by the same token, I can't see the Balrogs serving Sauron directly, given their more or less equivalent status and their different roles...