Admiralty - COMINCH

Operational Intelligence Center (OIC) Serial Messages


On the left is CDR Rodger Winn, the head of the Admiralty's Operational Intelligence Center - On the right, his counterpart on the COMINCH staff, CDR Kenneth Knowles



Historian David Kohnen's book Commanders Winn and Knowles: Winning the U-boat War with Intelligence 1939-1943 provides an excellent explaination of the development and working of the Admiralty and COMINCH Operational Intelligence Centers.  It is highly recommended as a companion to the records presented in this section. The book is puplished by The Enigma Press, April 2 1999, ISBN 8386110341

It is not the practice of this website to sell books or any other items but since the book is not generally available the administrator notes that it can be purchased direct from the publisher for USD 25.00 (surface) and USD 30.00 (air) Orders to: The Enigma Press, Podedworze 5, 32-031 Mogilany, Poland, or by e-mail:    Arrange method of payment on direct contact.
The book is also available at
        The records below are a subset of the correspondence between the Admiralty and COMINCH OICs.  Other record sets include:  logs of attacks, bi-weekly U-boat trends, tracking room memorandums and U-boat position estimates.  The administrator intends to make these records available in the future.
       These records a part of the United States National Archives Record Group 457 (the initial set offered below are specifically SRH-208 and SRH-236) They were formerly National Security Agency/Central security Service Cryptologic Documents Offered to and accepted by the National Archives in June 1984.  Copies of these documents are maintained in several locations.  The particular copy transcribed on this website is from the Air Force Historical Research Agency located at Maxwell AFB, Alabama.  Click the icon below to proceed to the Air Force Historical Research Agency website.
Air Force Historical Research Agency

        A post war study of Allied communications intelligence in the U-boat war can be found in another document from Record Group 457 - Battle of the Atlantic: Allied Communication Intelligence December 1942 - May 1945.  This document has been transcribed and presented on the web by Patrick Clancey of the HyperWar Project.

       The reader's attention is called to Chapter II: The U-boat and Allied Naval Communication Intelligence, page 20 which contains a table titled: Record of U-boat Traffic Decryption (Atlantic) December 1942--May 1945.  This table gives the time late of decrypting U-boat messages by Op-20-G for each month of the war.  Time late is key to understanding the usefulness of the information derived from decryption of U-boat wireless traffic.  It is important to note that while Op-20-G (or Bletchly Park) could decrypt the text of a U-boat message, the naval grid square was further encoded.  The OICs had to work out the actual grid square based on other information such as D/F, interaction with Allied units and their understanding of U-boat operations.  The capture of the code book used to encode naval grid squares aboard U-505 in June 1944 enabled the OICs to read the actual naval grid square without guesswork or delay.

Click the icon at left to view this record on the HyperWar website
       The bigram search engine herein was programmed by Mike Holdoway whose Convoy Web website provides a wealth of information on South Atlantic (and other) convoys including the complete convoy database collected by the late Arnold Hague detailing about 28,000 individual convoys.  The site also provides many useful extras such as a calendar and sunrise/ sunset times for 1939-45, a distance calculator and Kriegsmarine charts.  I am very grateful for his help with this project.
Click the icon at left to proceed to Convoy Web



Click the icons to view the associated records
Months outside the period covered by serial messages
Months for which records are available - click on hypertext to view the record
Admiralty Bigram System
Terminology used in COMINCH - Admiralty serials
Photographs related to the COMINCH OIC