ABSTRACT
This collection of essays is mainly devoted to the most important form of twentieth-century intelligence gathering before the emergence of the spy satellite: signals intelligence (sigint) derived from various technologies of interception and the work of codebreakers and cryptanalysts. The final article, however, is a reminder of the continued importance of much more traditional forms of message interception. The ancient, if often dubious, art of the letter-opener still survives in an intelligence era increasingly dominated by ever more sophisticated means of technical collection.
