Secret Messages

Codebreaking and American Diplomacy, 1930-1945

David Alvarez

To defeat your enemies you must know them well. In wartime, however, enemy codemakers make that task much more difficult. If you cannot break their codes and read their messages, you may discover too late the enemy's intentions. That's why codebreakers were considered such a crucial weapon during World War II.

In Secret Messages, David Alvarez provides the first comprehensive analysis of the impact of decoded radio messages (signals intelligence) upon American foreign policy and strategy from 1930 to 1945. He presents the most complete account to date of the U.S. Army's top-secret Signal Intelligence Service (SIS): its creation, its struggles, its rapid wartime growth, and its contributions to the war effort.

“David Alvarez packs a lot into this rather short, brilliantly written and argued account of the US signals intelligence (Sigint) effort against foreign diplomatic communications. A must-read.

—Intelligence and National Security "Alvarez recaptures the wartime spirit of the Army code-breakers with verve and vigour. He tells us of SIS's sometimes bizarre and often obfuscating security arrangements; the perpetual bureaucratic infighting for more people, more space, more money; the role of women and minorities; and how people coped with their new experiences. In sort, he puts a human face on the heretofore impersonal code-breakers, giving the book an added dimension that makes it unique."—

“Secret Messages is a badly needed history of the origins of modern American signals intelligence.

—H-Net Reviews
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Alvarez reveals the inner workings of the SIS (precursor of today's NSA) and the codebreaking process and explains how SIS intercepted, deciphered, and analyzed encoded messages. From its headquarters at Arlington Hall outside Washington, D.C., SIS grew from a staff of four novice codebreakers to more than 10,000 people stationed around the globe, secretly monitoring the communications of not only the Axis powers but dozens of other governments as well and producing a flood of intelligence.

Some of the SIS programs were so clandestine that even the White House—unaware of the agency's existence until 1937—was kept uninformed of them, such as the 1943 creation of a super-secret program to break Soviet codes and ciphers. In addition, Alvarez brings to light such previously classified operations as the interception of Vatican communications and a comprehensive program to decrypt the communications of our wartime allies. He also dispels many of the myths about the SIS's influence on American foreign policy, showing that the impact of special intelligence in the diplomatic sphere was limited by the indifference of the White House, constraints within the program itself, and rivalries with other agencies (like the FBI).

Drawing upon military and intelligence archives, interviews with retired and active cryptanalysts, and over a million pages of cryptologic documents declassified in 1996, Alvarez illuminates this dark corner of intelligence history and expands our understanding of its role in and contributions to the American effort in World War II.

About the Author

David Alvarez is a professor of politics at Saint Mary's College of California and a former scholar-in-residence at the National Security Agency's Center for Cryptologic History. A frequent contributor to such journals as Cryptologia and Intelligence and National Security, he is coauthor of Nothing Sacred: Nazi Espionage against the Vatican, 1939-1945 and editor of Allied and Axis Signals Intelligence in World War II.

Additional Titles in the Modern War Studies Series