From the calling into existence of the first organized units of African American troops during the Civil War until the late 1940s, the armed forces of the United States were segregated by race. Given the prevailing racial attitudes, especially within America's military leadership, the process of integration was relatively slow paced, even after President Truman's 1948 Executive Order officially rendered segregation in the military inoperable. Even civilian employees in the U.S. defense establishment endured the pains of segregation and the slow evolutionary path of its demise. "The Invisible Cryptologists: African-Americans, WW II to 1956" is a study of one small Government agency's journey away from racial injustice. During World War II, what was then the Signals Intelligence Service (SIS) began hiring African Americans, up until then employed mainly as messengers, to decipher commercial telegraph codes that might contain valuable information emanating from companies in Tokyo, Berlin, and other international locations. After the war, the machine section (or "the plantation," one of its numerous unflattering nicknames) used African Americans to transfer Russian intercepts from radio tapes to punch cards - a tedious job in hot and dirty conditions without any realistic possibility of promotion up and out.As this monograph documents, things began to change as Truman's Executive Order and other developments ushered in an era when jobs as polygraph operators and, by the 1950s, linguists and analysts, began to open up. "The Invisible Cryptologists" is at its best when it not only tells the story of American segregation and integration, but allows some of the characters in that story to speak for themselves. As one former employee said, "I was so involved in what the Agency stood for, and I wanted it to be better. I had a feeling things were going to get better. Everybody in there was not evil. I felt that one day African Americans would be able to break out of this box." Those interested in African American history, the evolution of integration in the armed forces and American society, and the first-person stories of those whose lives were so profoundly affected by this crucial historical development will find " The Invisible Cryptologists" of great value.