[Raynor]

Sauron is certainly capable of commanding certain people (or even armies, as seen in the last battle) - that is, if he focuses on them. In Myths Transformed, Tolkien talks about orcs starting fights among themselves when Morgoth is not around, thus acting against his will and plans - and we certainly see this in the fights of the Cirith Ungol tower, or the fight between the sniffer orc and his companion who came about Frodo and Sam. I doubt that, even with the help of the one ring, Sauron can eradicate permanently the free will of all his subjects.