: Good point, but perhaps the Ringwraith served Sauron willingly, having been corrupted by him during their period of servitude. Or, like Saruman, served him for their own purposes.

: Still, it's food for thought, thanks.

You're welcome.

Another aspect is what was Sauron's main objective in regaining the Ring, was it so that he would regain any powers he had lost, or was it mostly out of fear of it falling into the hands of another being powerful enough to use it or destroy it? As he seemed to be doing quite well without having the Ring in his possession the latter reason would appear to be the stronger.

Tolkien said that Sauron invested a large amount of his native strength in the Ring. This raises a question, was Sauron an appreciably stronger being after the Ring was made, or was it just a tool to enable him to gain his objectives more easily? In other words did the Ring magnify his power or just focus it? I would tend to think the latter.

One of the things which distinguishes Sauron from Morgoth, to me, is that Sauron is much more interested in dominating and controlling others than Morgoth. Morgoth seems to be a petulant child writ large, his main motives are to destroy or pervert the works of others, especially those of Eru. Morgoth's motives appear to be based on pride, envy and spite; he cannot create so he spoils the creations of others. Sauron, whilst sharing in these motives, seems to be more driven by the desire to dominate and control others, and be worshipped by them. One of his titles was "The King of Men."
The Ring, seen as a tool for a specific purpose - to enable the domination of others, had by the Third Age achieved most of Sauron's designs: the Dwarves were a remnant, the wars of the Second and Early Third Age had destroyed the power of the Eldar in Middle Earth, Numenor had been wiped out (did the Ring help Sauron in perverting the Numenoreans?), and a very substantial proportion of humanity worshipped Sauron as a God. Thus Sauron would not appear to be greatly in need of the powers of the Ring at the time of the War of the Ring, he chief motive must have been to stop it being destroyed or used against him.