About an hour in to the mission I discovered that Nazis are actually kinda dumb and you don't really have to be very careful at medium difficulty.
Also, i don't understand why there are non-lethal options in this game, but I suspect there may be liberalism afoot.
I should note - If I did knock a Nazi out I specifically went back and shot them in the head. Those ten guys were accidents. Would have gotten them if I could.
Was playing this co-op with a friend, and he was going around knocking the Nazis unconscious
So I went around shooting them in the face while they were incapacitated
Teamwork makes the dream work.