|(A) 1548||(W)||PES||TSJZ||UKTZ||42 x 18|
|Crib from (a)||SZ||Q.HA||EP|
|Crib from (c)||BL.||AWN.||.VLK|
|(C) 0317||(W)||NKB||ERSS||RSON||49 x 24|
|Crib from (b)||YRJ||BKNL||PVPJ|
Note (i) How (a) crash on second letter makes the association Bb, Cc impossible.
(ii) How use of 6, 7 or 8th letters of (Aa) would have spoilt the menu.
(iii) How latitude of (b) can be deduced with help of estimated position although Archery is incomplete.
(iv) How no use is made of very high temperature trigram in (b).
(v) That (A) and (C) is different times of day are NOT level starts. Though they have the same indicator they are in different 6-hourly period and are not in depth.
SHARK B-bars after March 1943.
When the 3rd edition of the new WW book was introduced on March 10th 1943, efforts were made to break Shark almost exclusively on B-bars. The B-bar period lasted from March 10 to the end of June and during this time 87 out of 112 Shark days were broken. In July a reencodement was required to break Caesar and Gamma and after these were broken there were sufficient 4-wheel bombes and good reencodements to make B-Bars only a secondary method.
The principles of B-bar cribbing had been studied before the change over to it took place, and B-bar links had been used in menus mainly derived from WWs. Very close co-operation was required between Hut 8 and Naval Section IV (Submarines), who produced all available information that might be useful in deciding which boat had sent which signal, the type of signal it might have sent, and the exact position of the sender.
Available sources included
(2) RFP and Tina