While we should always invoke the usual caveats about allegory, it is
nonetheless helpful to remember that Tolkien did inevitably draw some of most
powerful imagery from his wartime experience. Garth does give us some
valuable insight into the world that influenced Tolkien, though we do need to
remember that no writer simply recreates his experience in his texts.
Tolkien used his love of language, his fascination with Norse myth, his
compendious knowledge of Anglo Saxon and Nordic medieval literature, and his
ability to subcreate his own secondary worlds along with the sights, sounds,
and cultural/social responses to the War to paint his own canvas. What I
like about Garth's approach is that he delves into associtions that are largely
lost on modern readers far removed from the horrors of trench warfare.
Great summary and questions on this
talk!

Howe, Drowning of Númenor