The only thing I remember regarding The Great War was in the story where Jeeves is on loan to another family and Bertie is, sadly, nowhere to be seen. It's mentioned that after The Great War, lots of aristocrats were being made/under pressure to learn how to be more independent. They were *gasp* getting jobs. Bertie's absence was put down to him attending a school and going on a course to teach young gentleman how to look after themselves. Of course, he does terribly and winds up getting chucked out and having Jeeves return to his side. But that's the only reference I can remember...