You are wrong on almost every count.paulrward wrote:Hello All ;
I am going to butt in again. I do NOT believe that the messages that were sent to aircraft in the air were enciphered, especially those sent to single engine aircraft with small crews. The labor of receiving the message, writing out the message, getting out that humungous JN 25 codebook, deciphering the message, and then writing it out for the pilot would be overwhelming in a small floatplane.
I believe that all the messages sent from the Kido Butai to their scoutplanes were sent in ' clear ' . I may be wrong, but in the USN during the war, all the ship to air and aircraft to ship radio messages were in straight Morse.
Midway Inquest's Appendix B is a copy of the traffic to and from KdB, as logged on 4 June by US eavesdroppers. They did not intercept every message to or from the Japanese aircraft, but it is very clear that some of it was in plain language and some of it was encrypted. For instance, the message sent by Tone 4 at 0555 (Midway time), "15 enemy planes heading towards you", was not itself intercepted, by its retransmission by Tokyo was picked up and the log notes that "It is believed to be reporting 15 American planes (dive bombers?)". Clearly this message was in plain language, but due to garbling, lack of familiarity with Japanese message proforma or some other reason, it was not fully understood by the eavesdroppers. The next entry in the log, at 0635, is from HAMI4 (the call sign for Chikuma 4) and it reads "HAMI4 sends to MARI the controlling or senior station a four kana despatch". This certainly appears to have been sent in a code the US could not read at the time. The messages to and from MEKU 4 (Tone 4) and MARI (KdB) are likewise sometimes encrypted and sometimes in plain language.
The code or cipher used for ship-plane messages would certainly not have been JN-25. Undoubtedly a much simpler system was used, and not only for practical reasons. It would have been very stupid to have put a copy of one's most important operational code on every search plane, given the risk that a copy might be retrieved by the enemy from a downed aircraft.
Other navies also supplied their aircraft with a simplified code. The First Team, page 192, tells us that at 0815 on 7 May 1942 Yorktown copied a message from a scout that placed two carriers and four heavy cruisers about 200 miles northwest of TF 17. However, four pages later we learn that when the SBD landed back on Yorktown the pilot stated that he had spotted two heavy cruisers and two destroyers, and "a quick check revealed a coding error on the pilot's cipher pad".
So it is clear that in June 1942 both IJN and USN scouts carried codes or ciphers and used them, resorting to plain language in emergencies or when encryption was not required.