But I'm still convinced that at least the black armors are a wanted resemblance to the Wehrmacht or SS.
You are of course aware that the Wehrmacht - a.k.a. The Third Reich's regular army and thus the closest analogy to the Nilfgaardian units that make an appearance in both books and games - was NOT clad in black clothes but wore grey(ish) garb.

The "Waffen SS", the combat branch of the organisatzion that actually fought on the frontline (and was responsible for many of the worst war crimes and atrocities), was a comparatively small paramilitary force that was not officialy part of the army.
And while Sapkowski makes use of certain terminologies, references and incidents thoughout the books that have their origin undeniable in WWII and Nazi Germany, I always thought of Nilfgaard as Sapkowski's version of the Roman Empire, augmented by (somewhat arbitrarily conflated) details derived from various historical cultures and epochs.
@
Luxorek : Actually, most German-sounding names are found in the Northern Kingdoms.
However, I'm at a loss how this all ties into the Precious Cargo Quest. :question: