: What if Smaug had never attacked the lonely mountain? Its because of Smaug that Sauron was beaten.

My first post!
While there were many seeming coincidences which contirbuted to the third age unfolding as it did, I find those involving persons or manifestations of evil the most intriguing.
Didn't Gandalf make the comment "Evil oft will evil mar.", or something like that?
I think one of the most pervasive, and most powerful themes of Tolkien's works is that evil, by perhaps its most striking characteristic (in Tolkien's literature), selfishness and lust for power, is consuming and ultimately self-destructive. And we aren't talking merely about the evil in individuals blowing it for them, we're talking about the ubiquitous theme of power lust unmaking, by degrees and happenstance, the grander designs of evil in Middle Earth, ultimately manifested in Sauron and witenessed by his downfall.
Isildur, Gollum, Boromir, Saruman, Grishnak -- individual falls abound, each contributing to the ultimate fall of Sauron. No coincidence, I'd say.
Interestingly, the most notable exception to this thought in Tolkien's works seems to me to be the final fall of Morgoth, which occurred, ostensibly, really by no fault of his own, but rather by a greater host simply overwhelming him. Perhaps this is a theme that came to the fore Tolkien's thinking when he created the ring.