In the forums over on the Dragons, Knights & Angels web-site, I got asked a question about how I got the idea for writing the story I got published there, and this is what I came up with.
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Hmmm.... More often than the other way around, I start out with some very general image or impression and build a story around it. In most cases (including this one) I write the first few paragraphs of "teaser" before having a terribly clear of idea of what comes afterwards, and then work backwards and construct the plot around that. In this case I had slightly more to go on than usual, since I knew from the beginning that I wanted to write about the Thid Reich and that it would probably have something to do with ideas about "the transmigration of souls" taken from Jewish mysticism, but the process was basically the same.

Anyway, given that procedure, thinking about the origins of a story can be a little bit like thinking about the origins of a dream the next morning. In both cases, you can go back and untangle threads of symbolism, influence, etc., but there are always going to be ambiguities. At the actual moment of "hey, I'll bet *that* would be a cool story," none of that stuff is immediately clear (at least to me.)

So, given those caveats, I'll settle for mentioning some things that I was watching/reading/thinking about around the time I wrote it that got me thinking about WWII, the transmigration of souls and other relevant subjects:

Reading: "Divine Invasions: A Life of Philip K. Dick" by Lawrence Sutin...(For people who are interested, "I Am Alive and You Are Dead: A journey into the mind of Philip K. Dick" by Emmanuel Carrere, which I read later, is a much better written and more entertaining biography than "Divine Invasions.")

Thinking about: Along with Philip K. Dick's perceived mystical experiences, one of the real-life inspirations was reading about Karl Heinz Shneider, a German fighter pilot who had a crisis of conscience and engaged in acts of resistance like dropping his bombs into lakes and deserted areas.

Watching: "Europa, Europa" (that one should be self-explanatory.)

On the subject of WWII, I should also mention that (although it's been a while since I read it) Herman Wouk's novel "Winds of War" and the sequel "War and Remembrance" had a huge impact on me. The scenes describing in awful detail the German bombardment of Warsaw certainly left a residue in my mind as a sort of archetypal example of a war crime, one of the reasons I was interested in the mindset of some one on "the other end" of it. Sure, the blitz of London comes up more often in fiction than Warsaw does, but rather than being described in it's awful details, it usually functions in story lines as an excuse for British children to be sent off to the countryside to have adventures in magical kingdoms (e.g. "The Lion, the Witch and the Wardrobe" and "Bedknobs and Broomsticks"), so it's hard for me personally to feel horrified about it.

Beyond all that, I took four years of German in high school, I visited Astria once (to visit my sister, an amazingly talented fantasy novelist who spent, when you put it all together, almost two years living in and around Vienna and often uses it as a setting for her own stuff) and I've always had a certain level of fascination with all things Germanic. Plus, when I first started college, for a little while I wanted to be an archaeologist.

I don't know if any of that actually answered your question, but hey...