In December 1936, Joseph Selligman Jr. left Swarthmore College to enlist in the Spanish Civil War. "Please don't try to follow or catch me or anything," he told his parents. "Quit worrying," he also said. "I am in no danger." The first American to go into combat in the battle for Madrid, Selligman was shot in the head on Feb. 11, 1937.

Selligman was one of about 40,000 men from 50 countries to fight in the Spanish Civil War, which began with a coup backed by the military, large landowners and businessmen, conservatives, monarchists, fascists and Roman Catholic clergy (with military assistance supplied by Nazi Germany and Italy) against the democratically elected, left-leaning Second Spanish Republic (which depended on weapons supplied by the Soviet Union).

Angry that the United States remained neutral, American volunteers came from 46 states and many walks of life, but were predominantly New Yorkers, trade unionists, Jews and Communists.

In "Spain in Our Hearts," Adam Hochschild, the co-founder of Mother Jones magazine and the author of "To End All Wars," "King Leopold's Ghost" and "Bury the Chains," provides a sweeping, suspenseful and somber chronicle of the Spanish Civil War that is organized around the experiences of about a dozen Americans. At its best, the book captures the idealism, courage and illusions of its subjects as well as the significance "of the dark days that were just the beginning of the trauma and tragedy" that would become World War II.

Making superb use of diaries and letters, Hochschild re-creates battlefield conditions. In fighting on the campus of the University of Madrid, he indicates, Republican snipers appeared in lecture hall windows, behind barriers built of metaphysics and philosophy books. One of them calculated that a bullet could penetrate 350 pages before coming to a stop.

And Hochschild underscores the conflict's global nature by revealing that Torkild Rieber, the CEO of Texaco, violated the U.S. arms embargo by shipping oil (and extending credit) to the Nationalists — and received nothing more than a slap on the wrist from the government.

Hochschild's history is judicious. He documents atrocities by Republicans as well as Nationalists. But his heart is clearly with the Republicans. Hochschild heaps praise on the cooperatives and worker-controlled businesses that were run on a large scale, as a "fascinating, tempting example of a path not taken."

A member of the '60s generation who would like to believe he would have gone to Spain, Hochschild hopes his book will provide a "political ancestry" for those who care about social justice. Whether or not it does, "Spain in Our Hearts" will surely leave readers admiring the men and women who were willing to give everything to make the world more fair and free.

Glenn C. Altschuler is the Thomas and Dorothy Litwin Professor of American Studies at Cornell University.