At the outset of the war, Claude Houghton [Oldfield] enlisted, but was refused combat service because of his poor eye-sight. He served in a desk job at the Admiralty.
This is all I know currently about Houghton’s war service; it derives from Wikipedia.
It should be noted, however, that in one sense at least all his novels (Wikipedia lists 23 novels, two plays, and two collections of poetry, and two collections of short stories or essays) are inspired by the Great War. He stated, according to Brian Stableford, that all his work was based on the thesis that modern civilization must collapse “because it no longer believes it has a destiny”; and that is a characteristic post-war feeling.
Science Fiction and Fantasy Writers in the Great War 