People always try to read things as allegories for some reason, but one can naturally see the parallell to the mental scars war probably must leave. He might not have had the perspective to write something like that sentence without having been in a war himself, but that does not mean it is a direct reference to the war.

I would say retrospectively that the war might have given Tolkien deep enough of a perspective on war and the worlds light and dark corners to write something so deep and human like Lord of the Rings, which encompasses all of these elements. One can easily replace the rings with money or power to create metaphors for real life and so on, but that doesn't make the story an allegorical one. It just makes it a very layered and "close to things we know" type of story Imo :)