For me, I would liked to have known more about how and why humans (from Rhun, Harad, Dunland, etc.) had been convinced to ally with Sauron, Saruman, and/or the Witch-King. Some of it is covered in his works (the Dunlending Wild Men and their disdain of Rohan, for example), but I wonder the deeper causes when they had to see the atrocities that were committed by the dark forces, especially against other humans. I know much of it was based upon fear and even worship, but I think it would take a lot of brainwashing and deception of a whole region to believe that the dark forces would somehow set things right. Do you have thoughts on this? Which regions, cultures, story lines, events, etc., do you wish Tolkien had explored further?