SPAIN IN OUR HEARTS: Americans in the Spanish Civil War, 1936-1939. By Adam Hochschild. Houghton Mifflin Harcourt. 438 pages. $30.

Best-selling author Adam Hochschild has turned his attention to the Spanish Civil War in his fascinating new book, “Spain in Our Hearts.”

A co-founder of Mother Jones magazine, Hochschild is the author of several previous narrative nonfiction books, including “To End All Wars,” “King Leopold’s Ghost,” and “Bury the Chains,” the latter of which was a finalist for the National Book Award.

In each of his books, Hochschild combines dogged research with smooth writing. “Spain in Our Hearts” is an excellent new addition to his resume.

The Spanish Civil War, which raged from 1936 to 1939, began as a military coup led by Generalissimo Francisco Franco to overthrow the nation’s democratically elected government. Aided by Germany’s Adolf Hitler and Italy’s Benito Mussolini, Franco’s fight, as Hochschild notes, was “designed to maximize bloodshed.”

Part of that involved what was known as “limpieza,” Spanish for cleansing, in which Franco’s forces slaughtered tens of thousands, often leaving the dead in the streets as warnings and foreshadowing the larger horror Europe would soon experience.

During this time, no one was spared, including pregnant women. In one case near the city of Badajoz, Franco’s forces marched almost 2,000 people into the bullring and machine-gunned them. “There is more blood than you would think in 1,800 bodies,” Hochschild quotes an American journalist.

Fascist forces committed mass rapes, often using Moorish troops, which played off racial fears of many Spaniards at the time. One soldier in an interview with a British reporter scoffed at labeling such assaults as atrocities: “No senor. That was fun.”

Franco’s forces went so far as to execute an incendiary bomb attack on the city of Guernica, a precursor of the destruction of Dresden and London in a few years and which would lead to one of Pablo Picasso’s most famous paintings of the same name.

While Franco benefited from help via Germany and Italy, Spain’s elected government in contrast garnered no support from Western European countries such as France and Great Britain, or even the United States.

Despite then-President Franklin Roosevelt’s refusal to get involved, more than 3,000 American civilians volunteered to fight. Those Americas are the springboard Hochschild uses to tell the larger story.

The Spanish Civil War drew many celebrities, including then-37-year-old author Ernest Hemingway and his soon-to-be-third wife, journalist Martha Gellhorn. Hemingway, whose most recent books had performed poorly, came armed with a contract from North American Newspaper Alliance to write articles on the war. In addition, he would later use the experience as the basis for his novel “For Whom The Bell Tolls.”

Another soon-to-be household name was British author George Orwell, who stood 6-foot-3, making him an easy target.

A sniper, in fact, shot Orwell. “There seemed to be,” Hochschild quotes him as writing, “a blinding flash of light all round me, and I felt a tremendous shock — no pain, only a violent shock, such as you get from an electrical terminal; with it a sense of utter weakness, a feeling of being stricken and shriveled up to nothing.”

But it wasn’t all big names.

Hochschild notes that African-Americans fought side-by-side with their white countrymen, only to return home to the United States to suffer discrimination. “Spain,” he quotes one such soldier, “was the first place I ever felt like a free man.”

One of Hochschild’s great strengths is his incredible eye for those telling small details, like the priest in Guernica who turned to communion wine to extinguish an incendiary bomb or how troops used bacon fat to grease their rifles.

Those visuals are only part of what makes Hochschild such a strong storyteller, who with each page develops a fascinating cast of characters that drive the narrative.

Furthermore, thanks to his continued focus throughout the narrative on the 30,000-foot view of history, Hochschild helps illustrate how the struggle for Spain was only the warm-up for the large-scale horror the world would soon witness.

Reviewer James Scott is the author of “Target Tokyo,” “The War Below” and “The Attack on the Liberty.” He lives in Mount Pleasant.