Elwin Ransom
Elwin Ransom may be based on C. S. Lewis' friend J. R. R. Tolkien ("Elwin" means "Elf friend" in Anglo-Saxon), though he seems to have autobiographical elements. In "That Hideous Strength" Ransom, with his royal charisma and matter-of-fact breezy acceptance of the supernatural, appears less like Tolkien than like Charles Williams (or some of the heroes in Williams' books).
J. R. R. Tolkien
On 27 October 1916, as his battalion attacked Regina Trench, Tolkien came down with trench fever, a disease carried by the lice. He was invalided to England on 8 November 1916. Many of his dearest school friends were killed in the war. Among their number were Rob Gilson of the Tea Club and Barrovian Society, who was killed on the first day of the Somme while leading his men in the assault on Beaumont Hamel. Fellow T.C.B.S. member Geoffrey Smith was killed during the same battle when a German artillery shell landed on a first aid post. Tolkien's battalion was almost completely wiped out following his return to England.
Tolkien might well have been killed himself, but he had suffered from health problems and had been removed from combat multiple times.