Alvarez (politics, Saint Mary's College of California) traces one chapter in the history of cryptology. Drawing upon military and intelligence archives, interviews with retired and active cryptanalysts, and recently declassified cryptologic documents, he examines the contributions that the U.S. Army's top-secret Signal Intelligence Service (SIS) made to the war effort before and after World War II. Alvarez traces the development of the SIS and describes the code-breaking process. He also considers the relationship between intelligence and foreign policy. Annotation c. Book News, Inc., Portland, OR (booknews.com)