Albert Speer said this quote

I do not think that in those early days of September, Hitler was fully aware that he had irrevocably unleashed a world war. He had merely meant to move one step further. To be sure, he was ready to accept the risk associated with that step, just as he had been a year before during the Czech crisis; but he had prepared himself only for the risk, not really for the great war.

~ Albert Speer