I did a google for hits on Churchill, Roosevelt, November, 26, 1941, to see what might materialize.
It would appear the one telegram was certainly sent from Churchill to Roosevelt at about 3 AM (London). It apparently has been found and the contents (such as noted on that website article) seems innocuous. The article indicated that it was put forward that a later telegram was sent that day but has never been found.
The issue appears to be that one of the proponents of the idea that Churchill conspired with Roosevelt (i.e. Churchill told Roosevelt but they kept it quiet) or that Churchill never told Roosevelt, was supposedly involved with breaking JN-25 back in 1939. It was refered to as the Japanese naval cypher.
I would point out that supposedly JN-25b went into force around December 1940 and remained in force until nearly June 1942. While participating in the solution of an earlier version (circa 1939) of JN-25 would provide clues that would assist in solving a new edition (circa 1940), it is a bit of a stretch to assume that JN-25b had been so thoroughly broken that the British would know all the details of the Pearl Harbor attack. The proponent's knowledge being limited to the previous edition (1939) means that he is only able to speculate that IF the code was thoroughly broken (as in 1939, a fact I am not going to research) such a plan to attack Pearl Harbor might have been solved.
I would note that TCB says the US and UK code breakers in the Pacific worked together (as best I assume as one may) and assisted each other. Assuming that was true, one has to then assume that the UK chose to conceal its progress in solving JN-25b and do so in a comprehensive and utterly distrustful way. There was no way to predict that a Pearl Harbor attack message would be intercepted and reduced to plaintext by only the UK, so the basis for concealing their progress is lacking.
Note that the deception (that JN-25b had been effectively solved) would have to extend past the beginning of the war, at least until a new edition came into force, because a sudden release of a whole host of heretofore unknown code group meanings would have, at a minimum, aroused suspicions among the US code breakers who themselves know how hard it was to solve codes.
It would appear the one telegram was certainly sent from Churchill to Roosevelt at about 3 AM (London). It apparently has been found and the contents (such as noted on that website article) seems innocuous. The article indicated that it was put forward that a later telegram was sent that day but has never been found.
The issue appears to be that one of the proponents of the idea that Churchill conspired with Roosevelt (i.e. Churchill told Roosevelt but they kept it quiet) or that Churchill never told Roosevelt, was supposedly involved with breaking JN-25 back in 1939. It was refered to as the Japanese naval cypher.
I would point out that supposedly JN-25b went into force around December 1940 and remained in force until nearly June 1942. While participating in the solution of an earlier version (circa 1939) of JN-25 would provide clues that would assist in solving a new edition (circa 1940), it is a bit of a stretch to assume that JN-25b had been so thoroughly broken that the British would know all the details of the Pearl Harbor attack. The proponent's knowledge being limited to the previous edition (1939) means that he is only able to speculate that IF the code was thoroughly broken (as in 1939, a fact I am not going to research) such a plan to attack Pearl Harbor might have been solved.
I would note that TCB says the US and UK code breakers in the Pacific worked together (as best I assume as one may) and assisted each other. Assuming that was true, one has to then assume that the UK chose to conceal its progress in solving JN-25b and do so in a comprehensive and utterly distrustful way. There was no way to predict that a Pearl Harbor attack message would be intercepted and reduced to plaintext by only the UK, so the basis for concealing their progress is lacking.
Note that the deception (that JN-25b had been effectively solved) would have to extend past the beginning of the war, at least until a new edition came into force, because a sudden release of a whole host of heretofore unknown code group meanings would have, at a minimum, aroused suspicions among the US code breakers who themselves know how hard it was to solve codes.
