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.InSecret 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.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...