Tolkien was sent to war when the new age of mechanical weapons were introduced. Machine-guns, tanks and poison gas. He fought in the Battle of The Somme, which is where over a million people were killed. You can see his experiences shine through especially in the fight scenes in the films..
You can also see his anger towards the massive cities that churn out great products in quick succession, and that end up destroying the urban land because of the size of factories. This can be seen in the story when Saruman destroys a wide part of the forest to make way for his new army..
Even though the books are a fantasy to most people, it can be as a way in which Tolkien voiced his philosophical opinions to the world about life