To be more accurate, he was in the trenches during WWI, the first real mechanized war with chemical warfare, tanks, airplanes, machine guns, etc.
When Hitler was doing his crazy crap in the mid-late thirties is when he really started writing these books.
His relationship with CS Lewis & their discussions about Catholocism, his experiences in WWI as a doughboy, and his observations of WWII while getting bombed in England helped shape the story as it relates to the struggle between good & evil.
He clearly had strong opinions about the use of technology for violence. But that's the stuff that makes you think and distracts you from the special effects.
Not to mention the conflict between good & evil in Gollum, which you can write forever about. I actually did in college.