before, sets of tables were reissued for a second period of about six days about a month after their first appearance. When this was happening (as in most of December and February), Shark was often current.
The principle on which Archery, WWs, and signatures were associated has already been explained. Apart from incorrect tie-ups there were several other reasons why WW menus might fail:
(a) Incorrect Archery: As far as possible only trigrams confirmed by decodes on two different tables were accepted. Next best were trigrams whose equivalents were well confirmed in previous traffic.
(b) Some German Operators never realised (though told) that the order of tables 6, 7, 8, in the WW book did not correspond to the order in which their respective letters occurred in the WW. Several boats always put Wind after visibility and cribs of the 6th, 7th, and 8th letters of a WW were better left out of menus.
(c) Indicator tables were sometimes used wrongly (especially near the times for changing the column used) and indicator letters sometimes misheard.
It is worth noticing that in the 2nd Edition of the WW book a complete piece of Archery did not produce a unique crib for every letter of WW.
Example of WW cribbing. (This example is specially constructed)
Instructions decoded: U 532 and U 668 are to send WWs between 0020 and 0400 tomorrow morning.
Positions estimated by Naval Section
U 531 (LK) 53 x 33
U 668 (PJ) 48 x 21
|(a) 00430||17016||28200||187..||.0000||04700 003..|
|(b) ...90||25003||20802||966(15||9)7705||07500 003..|
|(c) 00520||31003||20823||98603||16708||07500 003..|
(Note: In Archery, the position is given by figures 3, 4, 5, 6, 7, & 8; in (a) 43.0 x 17.0)
WWs with T.O.O. and position estimated from D/F. The crib is written beneath in each case