[142]      COMMUNICATION INTELLIGENCE SUMMARY, 6 November, 1941
 
General.-Traffic volume slightly above normal. Receiving conditions were  fair, regular strong but heavy static on night watches interfered  somewhat. Today the specific call-up on the Tokyo broadcast was  eliminated. Formerly Tokyo radio called the unit concerned when the  dispatch was addressed to a member of that unit. Beginning yesterday  afternoon all broadcast messages are addressed to a single call without  regard to the addressee of the message. The recovery of the radio  organization will be hampered by this new advance in Communication  Security. Moreover there were nine messages today on this broadcast from  which the address and originator were missing. This may be the start of  complete elimination of headings on broadcast circuits. Tokyo addressed  a WIWI message to the Chiefs of Staff of the Combined Fleet and  Submarine Force.
Takao-Bako Area.-It is now certain that there is a very heavy air  concentration on Taiwan. This comprises practically the entire Combined  Air Force including the Commander and his staff plus at least one  carrier division and an unknown amount of the fleet air arm. No  additional units of the Third Fleet were located there today but it is  believed that CinC Third Fleet is now en route BAKO from SASEBO. From  traffic association it is believed that some Second Fleet units are in  Takao area but this has not yet been proven. The South China Fleet  Command has been active in dispatches to Taiwan addresses.
Combined Fleet.-A large amount of Combined Fleet traffic is now  appearing with secret (tactical) calls in use.
Mandates.-The Mandates traffic has dropped off somewhat. The Sixth  Defense Force at Truk and the RNO PALOA continue to be the most active  units.

 

(FROM: U.S. CONGRESS JOINT COMMITTEE ON PEARL HARBOR ATTACK HEARINGS; PT.  35, THE CLAUSEN INVESTIGATION, PP. 62-81. EXHIBIT "A" DAILY COMMUNICATION INTELLIGENCE SUMMARIES)