So, in the comments on my previous post (which comments I thoroughly enjoyed, by the way), David B. made the point about all the talent lost in the War, both those who had already made significant achievements (whose future work we lost) and those who were nipped in the bud, to use seriously what has long since become a cliche: killed so young that they left almost nothing behind.
Of major voices that belong to the first category -- writers of known greatness who died too soon because of the war -- three particularly stand out from my point of view.
First, SAKI. Hector Hugh Munro's mordant wit and cynical hilarity were unique and irreplaceable: think P. G. Wodehouse crossed with Edward Gorey. He's what Evelyn Waugh tried and failed to be. Saki is lucky in one way in that while he died relatively young (mid-forties), he'd long been at the peak of his form and people knew a major voice had been silenced. They've forgotten it since, but that'd have been the same had he lived, given the to and fro of literary reputation and the undervaluing of those who, like Saki, excel mainly in the short story form (cf. Dunsany's fate).
Second, EDWARD THOMAS. I confess I'd never heard of Thomas till introduced to his work by a friend during a 1987 trip to England (the same friend who introduced me to the work of Philip Larkin*) -- a lapse which I count as a failure of our grad. school system. He's remembered today as "the English Frost" (i.e., Rbt Frost), but in his own day he was so admired, and rightly so, that young Frost (who was a good friend of his, by the way, whom he mentored) was known as "the American Thomas". There are other poets killed in the war, but Brooke and Owen are remembered for capturing the moment (of early idealism and later despair, respectively); I doubt if either wd have had much more to say had he survived. Thomas was different. He was one of the greats, celebrating the quiet joys of English countryside, and his death and that of others like him actually changed the course of English literature, causing the emerging Georgians to be represented only by those minor poets who'd survived the war, thus opening the way to Eliot and Pound's Modernism.
Third, a name not many people have heard ranks in my mind as a major loss: WM. HOPE HODGSON. Hodgson is very much an acquired taste, but he makes the list for me because he wrote what I consider one of the finest fantasy novels ever written (it's in my top-ten list): THE NIGHT LAND. Whether Hodgson would have created any more major works had he survived was problematic -- after 1914 his works show a distinct tapering off as he sought a popular audience. But even if he'd been unable to recapture the level of his earlier works, a long life may have brought more attention to his work, including the early work that contains all his best. Or his early brilliance might have been buried under a flood of lesser stuff, as was the case with Dunsany (who did survive, barely**) or, to pick a non-war writer, Rbt Chambers. Or he might have recouped and gone on to greater heights, as is suggested by one of his last letters from the front, in which he talks about the blistering vistas he plans to incorporate into his work based on the things he's seen.
Of writers in the second category, those who did survive who'd achieved little before the war include Tolkien, of course, but also C. S. Lewis, who at the time he was serious wounded by shrapnel had written only SPIRITS IN BONDAGE (a worthy achievement in itself) and a few fragments like THE QUEST OF BHLERIS and the BOXON juvenalia. And far too many others, like G. B. Smith left behind even less than this.
**Dunsany was shot in the head, but this was by his fellow Irish during the rebellion, not German snipers.