also made it possible for eavesdroppers to listen in while foreign ministers
instructed ambassadors and commanders directed generals and admirals.
Governments accordingly established specially equipped intercept stations to
retrieve radio signals. If the recovered messages were encoded or enciphered,
governments resorted to the art of cryptanalysis to uncover their concealed
meaning. Many governments followed these ancient practices during World
War II and either established or expanded dedicated cryptanalytic agencies.
Cryptanalysts devised machines, embryonic computers, to solve messages
enciphered by other machines. For example, the British Bombe and Colossus
machines were developed specifically to decrypt messages enciphered by the
German Enigma and Geheimschreiber machines. The radio and cryptography
thus became locked in a symbiotic relationship with intelligence agencies.

Signals Intelligence similarly enhanced stratagem or deception.
Communications via radio widens the spectrum through which one can deceive
an opponent with false transmissions or dummy traffic. The ability to decrypt
the signals of an enemy similarly enables enemies to ascertain the impact of
disinformation on each other's intended victims as well as to determine the
credibility of double agents.

Compiling a volume devoted to Signals Intelligence in World War II
presented a number of organizational difficulties, not the least of which is the
fact that the components of the intelligence revolution overlap and interact with
one another in ways that preclude their isolation into neat categories. For
example, one cannot view ULTRA and MAGIC -- British and American
codenames for intercepts of German and Japanese communications -- unrelated
to cryptanalysis, military operations and deception or such famous actions as the
Coventry raid, the Battle of Midway and the "man who never was." Nor is
Signals Intelligence divorced from questions revolving around the organization
and politics of intelligence. In short, titles such as Anthony Cave Brown
Bodyguard of Lies and Reginald V. Jones' Wizard War are often relevant to
more than one facet of the Signals Intelligence story. Careful readers will
consequently note that selected titles occasionally appear under more than one
of the four main chapters of Signals Intelligence in World War II. They have
been cited more than once in the belief that their content is applicable to more
than one subject and to alert researchers to alternate sources in which they may
be found. Readers will also quickly discover that titles dealing with common
or related subjects, as the compromise of ULTRA by The Chicago Tribune, are
cross referenced. It is hoped that these practices will make this book a more
usable research guide.

Donal J. Sexton
Tusculum College
Greeneville, Tennessee

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