Hi All! I started this thread asking whether it would have been a sound plan for Holland to shadow Bismarck
and his destroyers for 24 hours instead of engaging at Denmark Straits, leading Tovey's force to her and engaging her with an overwhelming advantage of four capital ships to one. I appreciate all of the responses.
In this post: viewtopic.php?f=1&t=1810&st=0&sk=t&sd=a#p20853
I concluded that I don't think that my alternate scenario merit. It would be a radical departure from the traditions and doctrines of the Royal Navy that dictated immediate and aggressive action. It
would come under intense scrutiny if it failed. Holland and Tovey better have damn good reasons to justify it. Those reasons can only be based on things they knew or had high confidence in before the time of the Denmark Straits battle.
A. How Bismarck's Speed Affects My Scenario
I conclude that at that time they believed that Bismarck
had at least a two knot speed advantage on Holland's capital ships. Thus, among other things, Holland and Tovey had no choice but to assume that it could outrun radar or other shadowing when making their plan. This belief and assumptionshows up in Tovey's after action report, where he writes this:
. . . . . . .
From my point of view the greatest danger lay in his bugging the coast of
Greenland, and then making his way to the westward, where I suspected
he might have an oiler: for, if he could refuel, he would be able to use
higher speeds than the King George V could maintain
and so get away.
30. The enemy's alteration to the southward and his reduction speed were
a great relief
, although there seemed a good chance that he was leading
our forces into a concentration of U-Boats. It suggested that he did not know
of my force and it made interception possible.
31. There was still a grave risk of his getting away by sheer speed,
After my above post there has been a great deal of discussion of what Bismarck's
speed actually was
. I respectfully suggest that this misses the point of the thread. What matters is what Tovey and Holland believed
her speed to be relative to their own capital ships before they made a choice between shadowing or engaging at Denmark Straits. At (or after, if you prefer) the relevant time, Tovey believes that Bismarck
higher speed than KGV
and could get away. It follows that Tovey believed that speed was also higher than KGV's
, and since the latter was operationally tied to Hood
, as a practical matter faster than the speed at which Hood
could shadow. No other assumption would have been defensible for the limited purposes of my alternate scenario.
B. U Boat Threat
I also assume in my alternate scenario that the British had good reason to believe that Holland's shadowing force would not be lead into a U-Boat trap within the next 24 hours. Tovey mentions his concern that Bismarck would lead his force into such a trap and his relief because Bismarck's
lower speed suggests that she was not aware of his force. I think that Tovey and Holland knew enough to conclude that this risk was minimal and acceptable; they could intercept most if not all German naval transmissions, that the Germans knew that, and that the same was true in reverse. Without being able to decode and read them, they could rely on detecting changes in their pattern, timing or nature. A sudden increase in short and similar transmissions at regular intervals, each repeated several times, which pattern continues for many hours and begins after the shadowing started, would indicate a possible U-Boat trap.
a. The transmissions would have to start suddenly because there would be no reason to make
them until the shadowing started.
b. The transmissions would have to increase and be at regular intervals. The U Boats need the
British course and speed to intercept. This requires the Bismarck
to begin numerous
transmissions to provide the necessary data.
c. Each transmission would have to be repeated several times. The goal is to place a number
of U Boats, single or in a group, somewhere along the British track. Repeated transmissions
would maximize the number of U Boats that hear them - an obvious prerequisite to acting
act on them.
d. Tying together b. and c. above, each U Boat might not hear each transmission, so you have
to make enough to ensure that any of the the U Boats can miss some of them and still have
enough information to determine course and speed.
e. The transmissions would have to be short assuming that Bismarck
communicate the essential information - which is course and speed.
f. The transmissions would have to be similar if they only contain that essential information. In
this case the British could tell if they were similar for their purposes even if encoded. They
would have a sequence to compare, which would reveal a substitution pattern in the symbols
or characters used to convey the coded information. The duration and/or number of
characters or symbols would be the same. This suggests that each coded transmission
conveys the same type of information and has the same purpose.
g. The new transmission pattern would have to continue for a number of hours before even
a single U Boat could be in position to attack. Holland and Tovey knew that just about all of
operations would be at undetermined places in shipping lanes, that all U
Boats not dedicated to support the Rhine Operation would also be in shipping lanes, and that
U Boats are relatively slow. They could expect that the prepositions of the dedicated U
Boats would be where Bismarck would spend the most time and would be scattered because
the places where she might need support could not be foreseen. Thus there would be
ample time to react.
h. The threat from a single U Boat is minimized by the six destroyers in Holland's force, so
Tovey and Holland could regard the German's well-demonstrated skill at group attacks as the
real U Boat threat to the shadowers. Bismarck's
course and speed transmissions alone
would not be enough to gather several U Boats in the right place at the right time, each
knowing what they will do and what the others will do. A new series of transmissions is
required; either among the U Boats or one-way directions from land. I think that if the
British planned beforehand to look for such a second new pattern shortly after the first new
pattern from Bismarck
, they could count on intercepting enough of it to confirm that
the Germans were developing a multiple U Boat trap for the shadowers.
Considering all of this, in particular g. above, I think it was sloppy for me to say that the British knew beforehand that their shadowers would be safe from U Boat traps for 24 hours. Instead, if the amount of time beginning of Holland's shadowing and ending with Tovey's interception was less than that required for a U Boat to move from the nearest shipping lane to the interception point, the British had a sound basis for the conclusion that there was no significant U Boat threat to the shadowers.