Army Talks
The US War Department circulated weekly lecture/discussion booklets on topics of interest to GIs, ranging from the abstract, such as US foreign policy, to the practical, such as living in the field. The scans are of varying quality, and the un-proofread OCR'd versions (text, epub, etc.) range from worthless to mind-destroying, but if you're looking for a view of countries and regions the world from a soldier's perspective, there is nothing better. The first link goes to a general search, followed by selected items of specific interest to us.
If you are writing anything to do with the characters' pre-HH experiences, such as how they got to Stalag 13, the 8th Air Force issues are essential, especially "On Base" and "Day and Night". "Homefront USA" has an excellent section on what a soldier isn't allowed to say in a letter home. In addition to the specific volumes linked below, the Internet Archive has quite a few more, all of them interesting. You can find them at the first link on the list.
- Army Talks - The complete list of search results.
- You're Really in the Army Now - An introduction to military life.
- What Are We Fighting For? - Causes of the war and the future of peace
- What's Wrong with the Germans? - And why do they start all these wars?
- Pattern for Air Victory - Progress of the air war. A must-read.
- Day and Night - The 8th USAAF and the RAF
- Air Power - Goals and successes of the air war
- On Base - Life and operations of a bomber base
- See Yourself as Jerry Sees You - An overview of German propaganda
- Combat Medicine - The state of the art
- Homefront USA - The information on mail censorship is especially useful
- What You Should Know About France - A GI's introduction to liberated France.