"Frodo and Sam crawled after him, until they came to a wide almost circular pit, high-banked upon the west. It was cold and dead, and a foul sump of oily many-coloured ooze lay at its bottom. In this evil hole they cowered, hoping in its shadow to escape the attention of the Eye."
without seeing visions of the young Lt. Tolkien huddled with his men in a noisome trench, hoping desperately to avoid snipers and artillery. The entire transit of the Marshes of the Dead was like that; a grinding agonizing crawl that you felt in your bones.
That's one thing that Tolkien has that his thousands of imitators do not, an utterly physical sense of the ground he is sending his characters across. You felt it in the Shire, in the knowledge of how close and hot it could grow in dells under the trees and how cutting the wind on a hilltop could be even on a warm day. I would be surprised if Tolkien wasn't fond of hiking, and equally surprised if he was fond of riding, because his horses lack the sense of reality that is so present on foot. What a snarky fantasy author called 'magic horse syndrome' -- no saddle soreness, no having to stop to graze.