For some time he had been using captured Russian agents to communicate false intelligence to the Soviet armies, using their own codes and their own wireless sets; and it would have been entirely possible for him to enter into detailed communication with the enemy by this means without anyone being the wiser. Be that as it may, like a perfect Civil Servant, he went, leaving not a trace, his files totally destroyed.
[Mueller] had rather funny eyes which he would flicker from side to side with the greatest rapidity, and I suppose that this was supposed to strike terror into the heart of the beholder
He worked anonymously, and he has left hardly a trace behind. We find his signature on orders authorising the most atrocious deeds. We glimpse him once or twice in action, and are surprised to discover that this man without a shadow, this office bureaucrat, could walk about and use a gun. But we know nothing about him, neither where he came from nor where he went. Even his subordinate, Eichmann, the murderer of the Jews, who never on any account put his signature to a document, left behind friends and acquaintances who have given us vivid glimpses of the man. Mueller left nobody. We see him lunching at the Adlon Hotel with Heydrich, Nebe, Schellenberg, later with Kaltenbrunner. They are all dead. Even Willy Hoettl, who has things to say about most people, can tell us nothing about Mueller.
He [Müller] was an archetypal middle-rank official: of limited imagination, non-political, non-ideological, his only fanaticism lay in an inner drive to perfection in his profession and in his duty to the state - which in his mind were one... A smallish man with piercing eyes and thin lips, he was an able organizer, utterly ruthless, a man who lived for his work.
Müller was a stickler for duty and discipline, and approached the tasks he was set as if they were military commands. A true workaholic who never took a holiday, Müller was determined to serve the German state, irrespective of what political form it took, and believed that it was everyone's duty, including his own, to obey its dictates without question.
Richard J. Evans
Most of his social life was confined to such officials as HUBER, PIFFRADER, GEISLER, MEISINGER and GOTTHALMSEDER. …When I met him for the first time, I did not notice any peculiarities. He had a remarkably small figure, a piercing look in his dark eyes and there was, in his appearance, nothing frank and kind but rather ‘luring’. He was, however, polite (“korrekt”) but perhaps too modest.MÜLLER had a remarkable memory and knew every person who had ever crossed his path and all events.
Mueller was dry and laconic. Short and broad, with the squarish skull of a peasant and a jut- ting forehead, he had tense, narrow lips and penetrating brown eyes, hooded by nervously twitching eyelids. His hands were wide and massive, with fingers as square as a match- box
He was the unobtrusive type of police official who leaves no personal impression on the memory. Later, all I could remember was a pair of piercing grey-blue eyes, fixed on me with an unwavering scrutiny. My first impression was one of cold curiosity and extreme reserve.