Hi,
THere is a good article with some quotes from TOlkien himself on this topic. Check out:
http://www.fotf.org/pplace/pi/lotr/A0018586.cfm
I was especially fascinated by the quote,
"The Lord of the Rings," he wrote in a letter to a friend, "is of course a fundamentally religious and Christian work; unconsciously so at first, but consciously in the revision."
So: when TOlkien started out, he was watching the story unfold; but when he revised it, I'm guessing that he realised he had Christian themes and concepts in there, and made them fuller.
--Mark12_30