[1] Bradford Hardie III, an American cryptographer during World War II, contributed insider information, German translations from original documents, and intimate real-time operational explanations to The Codebreakers.

William Crowell, the former deputy director of the National Security Agency, was quoted in Newsday magazine: "Before he (Kahn) came along, the best you could do was buy an explanatory book that usually was too technical and terribly dull.

The NSA considered various options, including writing a negative review of Kahn's work to be published in the press to discredit him.

[4] Kahn and Macmillan eventually agreed to remove some material from the manuscript, particularly concerning the relationship between the NSA and its counterpart in the United Kingdom, GCHQ.

The book was republished in 1996, and this new edition included an additional chapter briefly covering the events since the original publication.