Ultra Versus U-Boats: Enigma Decrypts in the National Archives

342 Pages·2008·14.28 MB·English

by  Roy Conyers Nesbit

By the same author
Woe to the Unwary
Torpedo Airmen
The Strike Wings
Target: Hitler’s Oil (with Ronald C. Cooke)
Arctic Airmen (with Ernest Schofield)
Failed to Return
An Illustrated History of the RAF
RAF Records in the PRO (with Simon Fowler, Peter Elliott and Christina
Goulter)
The Armed Rovers
The RAF in Camera 1903 – 1939
The RAF in Camera 1939 – 1945
The RAF in Camera 1945 – 1995
RAF Coastal Command in Action 1939 – 1945
RAF: An Illustrated History from 1918
Britain’s Rebel Air Force (with Dudley Cowderoy and Andrew Thomas)
The Flight of Rudolf Hess (with Georges van Acker)
RAF in Action 1939 – 1945
The Battle of Britain
The Battle of the Atlantic
Missing Believed Killed
The Battle for Europe

First published in Great Britain in 2008 by
Pen & Sword Military
An imprint of Pen & Sword Books Ltd
47 Church Street
Barnsley
South Yorkshire
S70 2AS
Copyright © Roy Conyers Nesbit, 2008
9781783409273
The right of Roy Conyers Nesbit to be identified as Author of this
work has been asserted by him in accordance with the Copyright, Designs and
Patents
Act 1988.

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available from the British Library.

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Table of Contents
Also by
Title Page
Copyright Page
Foreword
Preface
Acknowledgements
CHAPTER ONE - Opening Rounds
CHAPTER TWO - Survival after Defeat
CHAPTER THREE - British Counter-Measures
CHAPTER FOUR - A Critical Year
CHAPTER FIVE - The Height of the Battle
CHAPTER SIX - Defeat of the U-Boats
Bibliography
Index of U-boats
Foreword
By John A. Cruickshank VC
Those of us who flew in Coastal Command or its overseas equivalents during
the
Second World War had no knowledge of the decryption of enemy signals
achieved by experts at the Government Code and Cipher School at Bletchley
Park. Even after the war, this process remained secret for many years, although
the equipment developed led to the introduction of the modern computer.
Aircrew who flew in maritime aircraft assumed that our intelligence officers
must have gained knowledge of U-boat locations and movements via secret
agents operating in enemy territory or from prisoners of war. Pre-flight briefing
required aircrews in operational aircraft to hunt over certain areas of the sea, in
order to locate U-boats either visually or with our ‘Air to Surface Vessel’ radar,
and if possible to attack them.
These operational flights were long and often fruitless, with only occasional
bursts of intense action, but the interceptions and attacks became far more
frequent from 1943 onwards. We now know that the Ultra decryption of Enigma
signals was one of the main aids in the eventual destruction of the U-boat Arm
of the Kriegsmarine.
The author of this book was given special access to the National Archives
(formerly the Public Record Office), which holds the original teleprinted
translations of intercepted German U-boat communications. He has worked
through over 100,000 decrypts and selected almost 200 examples. These have
been captioned and arranged chronologically to represent the war against U-
boats. He has also picked out about 200 photographs to illustrate this vital aspect
of the war at sea. This is the first time that such a combination has been made
available to air and naval historians as well as to the general public.
Preface
Work on this book began several years ago, during a period when I was invited
by the Public Record Office (as the National Archives was then named) to help
promote the unique collection of photographs available in its Image Library.
This holds a huge number of images from the past, such as maps and plans,
advertisements, designs, posters, prison records, state papers, and photographs
which include both world wars. My specialism concerned the RAF in the Second
World War, and I wrote several illustrated books based on the numerous
photographs available and occasionally gave illustrated talks to the public in the
lecture hall.
Towards the end of this period, Paul Johnson of the Image Library pointed out
that Ultra decrypts of German Naval Signals relating to U-boats, which had been
released to the PRO from 1977 onwards, had received little publicity. There are
thousands of these in fifty-four files, and I gradually worked through all of them,
and eventually selected about 200 to represent the huge collection. These
examples were captioned after carrying out much further research, although it
must be said that some details are uncertain, since the precise evidence was
taken to the bottom of the sea. About 200 photographs were added, partly from
my own collection.
The decrypts in each file are arranged in chronological order, according to the
German dates of origin. They were decoded by cryptanalysts at the Government
Code and Cipher School at Bletchley Park in Buckinghamshire, translated into
English and then passed to the Operational Intelligence Centre of the Admiralty.
The signals sent back to base by the U-boats often gave their grid positions, thus
enabling the Allies to instruct their escort vessels and air forces to concentrate on
hunting in the correct locations.
The signals usually gave the number of the U-boat but sometimes only the
name of the commander, so that the present-day researcher needs to establish
that U-boat number from published books of reference. There is no separate
index of either U-boats or commanders in the files, so anyone researching a
particular boat might face quite a lengthy hunt.
The German war machine’s U-boat Arm was regarded by the Allies as a