On February 1, 1943, the U.S. Army's Signal Intelligence Service, a forerunner of the National Security Agency, began a small, very secret program, later codenamed VENONA. The original object of the VENONA program was to examine, and possibly exploit, encrypted Soviet diplomatic communications. These messages had been accumulated by the Signal Intelligence service (later renames the U.S. Army Signal Security Agency and commonly called "Arlington Hall" after the Virginia location of its headquarters) since 1939 but had not been studied previously. American analysts discovered that these Soviet communications dealt with not only diplomatic subjects but also espionage matters. Six public releases of VENONA translations and related documents have been made. These releases covered the following topics and are discussed in this monograph: Soviet atomic bomb espionage; New York KGB message of 1942 and 1943; New York and Washington KGB message of 1944 and 1945; San Francisco and Mexico City KGB messages, GRU New York and Washington message, Washington Naval GRU messages; KGB and GRU messages from Europe, South America, and Australia; Messages inadvertently left out of the previous five updates of previously issued translations. Updates to some translations by restoring names that had been protected for privacy reasons.