The author charts the volunteers' motivations for enlisting in the fight against Spanish fascism and places their actions in the context of the Depression era. The battleground experiences of the brigade have never before been depicted in such vivid detail, and such battles as Jarama, Belchite, and the Ebro come alive in the participants' words. The author uses the military aspects of the war to illuminate such related issues as the influence of political ideology on military events and the psychology of a volunteer army. He also closely examines the role of the Communist party in the conduct of the war, including the "Orwell question"—allegations of a Communist reign of terror in Spain—and investigates the alleged racial problems within the brigade, the first fully integrated military unit in American history.

The book continues the saga of the brigade by relating the problems of the surviving volunteers with the U.S. Army during World War II; their opposition to the Cold War, the Vietnam war, and U.S. intervention in Central America; the persecution during the Red Scare of the 1950s; and their involvement with the civil rights movement.