Prinz Eugen was running up - Bismarck was also out of the wharf......
.....The RN wouldn't know if Hipper or Scheer would not support the "Herbstreise". We know they were planned for Atlantic diversions. The RN didn't. The important point is how would the "Herbstreise" look from the British side. We
know it was a diversion.....And, talking about Ultra, there were also to be active radio deception going on at the same time.
They wouldn't know about Lützow, Scharnhorst and Gneisenau. The latter was "out" in October, I believe.
Actually Donald P. Steury in his article "Naval Intelligence, the Atlantic Campaign, and the Sinking of the Bismarck: A Study of the Integration of Intelligence into the Conduct of Naval Warfare" (Journal of Contemporary History, Vol 22, No. 2) looks in part at just this subject.
British intelligence at this time relied primarily on radio direction finding and signals traffic analysis, HUMINT - agents reports and information garnered from Swedish naval sources - and direct surface and air reconnaissance. ULTRA had little impact on naval intelligence, since the KM Enigma codes were essentially secure until after the New Year. Luftwaffe decrypts did give some insights, especially on major ship movements, but otherwise the British relied on direction finding for German ship movements and signals analysis on ship identifications. Air reconnaissance was not used for the major KM ports at this time unless as part of a Bomber Command mission, which was unusual, Kiel and Wilhelmshaven were simply too well defended at this time. However, short-range coverage of the Low Country and French Channel ports was generally extensive. Otherwise it was the standing cruiser patrols covering the two possible routes out of the North Atlantic around Iceland that were critical.
So the British from pre-war intelligence had a good knowledge of German naval strengths and construction. They also had some reports of damage inflicted on German ships. they had pretty good means of detecting German attempts to breakout through the North Sea, but they were ny no means infallible (when the twins sortied in late January 1941 after completeing repairs in December 1940 - not October 1940 leandros, trying to pull one over on us again?
- Naiad actually tracked them for Hovey's massive sortie, but then lost them when Lutjen's turned away and ran north, allowing them to breakout into the Atlantic....British ship-based surface search radar wasn't as good as that on the German capital ships at this time).
But here are some of the problems.
1). The German diversionary plan, like all such, only works if the British detect
the German diversionary force. Otherwise there is no effect
on Seelöwe operations and British reactions. That means the Germans must risk actually losing their remaining capital ships by physically revealing themselves to British reconnaissance in the North Sea....and that cannot be done by ships docked at Kiel, Wilhelmshaven, or working up in the Baltic.
Which means the diversionary force is reduced to the three light cruisers and one training ship escorting the liners of Herbstreise. Which the forces at Scapa are more than adequate to deal with.
2). If British naval intelligence at this time is limited, German naval intelligence is non-existent.
Quite simply they had little idea of the strength or dispositions of the British fleet elements. The Luftwaffe was actively hostile on the subject of diverting reconnaissance elements to naval matters and the KM cooperation squadrons, such as they were, were fully tied up in helping to maintain operations in Norway. So there was little or no aerial reconnaissance of the British fleet bases.
Nor were there sufficient U-Boot to establish pickets off British bases, which after Royal Oak was pretty suicidal in any case. Anyway, Seelöwe required the use of all U-Boot assets available to try to close off the Channel entrances and would have required all boats on Atlantic patrol to be withdrawn as well.
Worse, the B-Dienst lost the Admiralty codes in August and did not get back into the new codes until late in the year. Nor did they have the high-frequency direction finding capability of the British, so could not use that do track British movements.
So German operations would occur in an intelligence vacuum. At best the 'diversion' would 'draw off' the Home Fleet elements at Scapa, which were there precisely for that purpose
. In other words, the 'diversion' would actually 'divert' nothing.