Title: The Codebreakers
Author: David Kahn
Kahn, David (1967). The Codebreakers: The Story of Secret Writing. New York: Macmillan
Date Updated: June 10, 2016
I read Kahn’s very long book The Codebreakers before taking a trip to Cambridge and Blechtley Hall to hear Nigel West give a series of lectures on espionage. The Codebreakers truly covers the field of cryptology and codes. It is pretty intense reading, and sometimes very technical, but that is exactly what I wanted.
In this work, Kahn wrote the most complete public treatment of the history or cryptography. Since his book was published, however, revelations about British success in breaking German ciphers in WWII have added a new and most important chapter to that history. Kahn’s own “update” can be found in Kahn on Codes: Secrets of the New Cryptology. New York: Macmillan, 1983
Kahn chronicles the history of cryptography from ancient Egypt to the time of its writing. The United States government attempted to have the book altered before publication, and succeeded in part. Bradford Hardie III, an American cryptographer during World War II, contributed insider information, German translations from original documents, as well as intimate real-time operational explanations to The Codebreakers.
The Center for Cryptologic History at NSA maintains a catalog of publications about the history of cryptology. It is divided into these sections:
- Pre-WWII (Prior to 1941)
- WWII Era (1941-1945)
- Cold War (1948-1991)
- Korean War Era (1950-1953)
- Vietnam War (1954-1975)
- The GUNMAN Project
These divisions are linked to documents in this web site that review each of the publications at the NSA site.
Reviewed by George C. Constantinides
Kahn observed that cryptanalysis was the most important form of secret intelligence but never had a chronicler. He regarded his work as a serious study of cryptology seeking to cover its entire history, with two goals: to tell how the various methods of making and breaking codes and ciphers developed, and how these methods have affected men. The consensus among both specialists and students (technical and nontechnical) is that Kahn certainly succeeded to a large degree. No one before him ever came near to doing what he did. More than half of the study deals with the twentieth century. Shulman in An Annotated Bibliograpy of Cryptography called this the best work of its type ever written, thorough in its treatment. Another writer called it the first in-depth history of cryptology, containing enormous quantities of information on the technology and development of cryptographic systems (Weber, United States Diplomatic Codes).
Kahn’s scholarship is prodigious, as is his knowledge of the subject. They are more characteristic of the professional cryptologist and scholar than of the amateur cryptologist and journalist that Kahn is. The notes and bibliography are themselves formidable and a gold mine of source material, including as they do some evaluations of reliability. Shulman observed that what faults there were are far outweighed by the strengths.
The main strength of the work, according to some experts, is that segment that covers cryptology up to World War II. The biggest and most obvious omission in it is the absence of full discussion of Allied successes against German cryptography, of Bletchley Park, and of the role of this communications intelligence in the 1945 victory. Kahn, it is said, knew something of these matters but was not able to expand this knowledge to deal with them since they were still highly classified. His refusal to attempt to do so on the basis of what he had is a testimony both to his good judgment and to his discretion. But he warns us at the start that his study is not exhaustive because secrecy still covered much of World War II cryptology. There may also be reservations with some of his assessments and judgments. Not everyone accepts unreservedly that Friedman alone made the U.S. preeminent in his field. A major landmark and contribution to cryptologic and intelligence history.
This is a review by the Defense Intelligence School.
A comprehensive history of secret communication from ancient times to the mid-1960s. The book provides both an historical survey of cryptology and considerable information on the science and methodology. It is by far the most comprehensive work of its kind. Unfortunately it was written before revelations concerning the British breaking of the German World War II codes, but this detracts only in small measure from the importance of this volume in this field.
Reviewed by Paul W. Blackstock and Frank L. Schaf
A scholarly world history of cryptology, eminently readable and highly informative, by a journalist-author, amateur cryptologist, and past president of the American Cryptogram Association, Although there is much in the book regarding the development of the technical aspects of cryptography and cryptanalysis, there is also much of interest regarding the evolution of organizations engaged in cryptology and the influence of cryptology on the course of war, battles, and world events. The chapters on Allied, Axis, and neutral cryptologic activities and organizations during World War II, and the 60 pages on the history and structure of the National Security Agency (NSA) in the postwar period, are especially informative. The bibliography plus the 155 pages of notes to the text represent a unique insight into signal intelligence source material.
 Constantinides, George C. (1983). Intelligence and Espionage: An Analytical Bibliography. Boulder, CO: Westview Press, pp. 262-263
 Weber, Ralph E. (1979). United States Diplomatic Codes and Ciphers, 1775-1938. Chicago: Precedent Publishers.
 Defense Intelligence School (1981). Bibliography of Intelligence Literature (7th ed Rev.). Washington, DD: Defense Intelligence School, p. 35
 Blackstock, Paul W. (1978) and Frank L. Schaf, Jr. Intelligence, Espionage, Counterespionage, And Covert Operations: A Guide to Information Sources. Detroit: Gale Research Co., p.