Presumably, in these days when patriotism is considered evil by the PC, it is easy to forget that Hitler made ISIS look like a sissy, and that the Battle of the Atlantic was going on, and that Germany had just conquered Norway and Iceland was the key to the North Atlantic sea lanes. (for history review of what was going on back then, check out this Podcast on the Battle of the NorthAtlantic here.)
So why shouldn't Lewis cooperate to help his country?
Most Lewis/Tolkien fans are aware that he got to know Tolkien when he joined a group that used the sagas to learn the Icelandic literature.
He spoke on the subject “The Norse Spirit in English Literature.” Lewis provided a touchstone between the Norse people and the English, which Lewis made clear in his first recorded statement. He said that he did not know why he had been asked to address the people of Iceland, but that he agreed to do it in order to repay a great debt. He explained that his imaginative life had been awakened by Norse mythology when he was 14. He went on to explain how his love of Norse mythology only deepened when he began to learn the Icelandic language at Oxford.
As for this comment:
well, maybe because his area of academic expertise was medieval and Renaissance British literature... but one might argue that the Icelandic sagas and mythology were a hobby that helped inspire his fantasy writings...
If Lewis felt so strongly about the Norse influence on the development of English literature, why did he never write on the subject later? We know that he felt strongly about the subject in his personal development, but why the great silence in his major critical works?
Tolkien might have been a more "logical" choice, but Tolkien was a deep scholar but lousy at lectures, whereas Lewis' lectures were famous for being easy to understand and for his enthusiasm.
in an unrelated item: Tolkien was approached to be a code breaker (he trained as a communications officer in WWI and had a background in this) but Tolkien had four kids and decided he couldn't afford to give up his job as a professor (i.e. that had tenure), and noted it was not his area of expertise.
related item: Right now, on Scribd, I'm listening to the audiobook of A Hobbit, a Wardrobe, and a Great War.
about how the war affected Tolkien and Lewis.
It's an easier read than Garth's encyclopedic book on Tolkien in the war, and it also brings up how religion was used to see the war as a great crusade (Jenkins has a book on this that I have not read).
The first few chapters is for the average reader who knows little or nothing about the cultural background of that war. I've only hit Chapter 3, which notes the Battle of the Somme, and the similarity of the horror of the trenches to the Dead Marshes in LOTR.
So I haven't hit the later part of the war, when Lewis arrived.