Here’s an article on how J.R.R. Tolkien’s novels were influenced by his experience in World War I.

The descriptions of battle scenes in “The Lord of the Rings” seem lifted from the grim memories of the trenches: the relentless artillery bombardment, the whiff of mustard gas, the bodies of dead soldiers discovered in craters of mud. In the Siege of Gondor, hateful orcs are “digging, digging lines of deep trenches in a huge ring,” while others maneuver “great engines for the casting of missiles…”

In “The Lord of the Rings,” we meet Frodo Baggins and Samwise Gamgee, Hobbits of the Shire, on a fateful mission to destroy the last Ring of Power and save Middle-earth from enslavement and destruction. The heroism of Tolkien’s characters depends on their capacity to resist evil and their tenacity in the face of defeat. It was this quality that Tolkien witnessed among his comrades on the Western Front…

Beside the courage of ordinary men, the carnage of war seems also to have opened Tolkien’s eyes to a primal fact about the human condition: the will to power. This is the force animating Sauron, the sorcerer-warlord and great enemy of Middle-earth. “But the only measure that he knows is desire,” explains the wizard Gandalf, “desire for power.” Not even Frodo, the Ring-bearer and chief protagonist, escapes the temptation.

Great stories tend to have a clear cut line between good and evil. In real life, we tell ourselves stories about good and evil, often to rationalize our own actions. But the vast majority of evil outcomes in the real world are not caused by intentionally evil acts, but by ignorance, negligence, and amorality. People don’t have the mental tools to understand and make good decisions about the complex systems we are all embedded in, and don’t think enough about right and wrong in their daily actions. How do you tell compelling stories about that?