Knowing exactly what anyone truly believes involves conjecture. People are actually capable of believing contradictory things and switching back and forth between those things within hours or minutes. For an excellent example of this human tendency, see George Collier's Socialists of Rural Andalusia, 1987, Stanford University Press. For more on how to assess beliefs (and how difficult it is to do so) see Clifford Geertz's Interpretation of Cultures (especially chapters 1-2).

Historians can tell you what documents say about what Hitler probably knew or was aware of; I know of no way for anyone to state what someone else truly believes. I have my own analytic standards for discussing beliefs, but Hitler isn't available as a subject to study (I study belief in living people).

So, I don't think anyone can say what someone truly believes (under certain circumstances, people form and unform beliefs very rapidly).

If you're asking for the opinion of a group of WW2 historians and want only those who have published in the area to respond with their opinions, that should be interesting. As someone who has studied (and published) on World War 2 (from an anthropological perspective), I can say that Hitler may or may not have looked at things from the point of view of "feasibility." I believe he felt he had something amount to a divine right to conquer Europe and actively kept his mind from incorporating information that might change his own mind. In other words, he data sorted. What did he think in the middle of the night? No one knows. Denial is a handy tool of the human mind, especially when beliefs are strongly held but challenged by thorny aspects of reality.

Hitler, in my view, had a complex (and somewhat addled) view about what warfare could accomplish (and had accomplished) historically. He was no Augustus.

I have no idea if anyone has written a psycho-biography of Hitler along these lines. Any psycho-historians out there?