August 30, 1862, proved to be yet another bloody day. Henry Clark was in the thick of things, fending off Federal troops in the Battle of Richmond, Kentucky, when the Confederate private caught an enemy shell in the thigh. Clark was swarmed by bluecoats and taken prisoner.

It was presumably when a Union medic treated Clark’s wound that the soldier’s tightly held secret was unmasked. Henry’s real name was Mary Ann. Indeed, she was a divorced mother of two.

When Federal troops realized that they had a woman on their hands, they moved quickly to release her—as long as she swore to return to the life of a proper lady. They even gave her a dress to wear. She agreed and was freed, then quickly cast off the frock and made her way back to the rebel army, where she was promptly promoted. Not long after, a young Confederate soldier—having joined a crowd gathered around Clark, then apparently serving openly as a female officer—wrote home: "Pa among all the curiosities I have seen since I left home one I must mention, a female Lieutenant."

A curiosity, yes, but to the surprise of many Civil War buffs even today, Clark was by no means unique. She was one of an estimated 400 women who took up arms in the war; they were not nurses, or laundresses or cooks, but actual female soldiers disguised as men, who marched, mastered their weapons, entered into battle and even gave their lives.

Various histories have alluded to women’s roles in combat during the War Between the States, but none have made so detailed and convincing a case as They Fought Like Demons: Women Soldiers in the American Civil War, to be published this month by the Louisiana State University Press. Coauthors Lauren Cook and DeAnne Blanton spent more than ten years combing through letters, archives and news reports to document some 250 women warriors.

"No one has accumulated this much data," says Cook, 46, who first tilled this turf in her 1994 An Uncommon Soldier (Oxford University Press), a compilation of letters from a female Civil War soldier. The authors’ mission was not just to catalog the combatants. Their extensive research convinced them that the prevailing notions about women’s participation in the war—that they had to be deranged or depraved—were way off the mark.

"We felt those women had not been given their due, that they were thoroughly misunderstood by military historians and the general public," says Cook, a special assistant to the chancellor for communications at Fayetteville State University-UNC in North Carolina. In fact, Cook contends, "they were just as successful as their male comrades, and what enabled them to be so successful was that no one knew that they were women."

Edwin C. Bearss, former chief historian for the National Park Service, is particularly impressed by the scope of the authors’ work. "I’m sure some will take issue with their conclusions," he says, "but this is a very significant study. They were able to document a far greater number of women than I, and others, thought they would."

What would compel a woman to march into that terrible combat—and how could she conceal her identity in what must have been uncomfortably close quarters? Blanton and Cook offer a number of persuasive answers. In the case of Clark, for example, a bad marriage and the death of a brother-in-law at the hands of a pro-Union mob took such an emotional toll that she sought refuge in the military, according to a letter from her mother uncovered by the authors. But Martha Parks Lindley joined up just two days after her husband left for the 6th U.S. Cavalry. "I was frightened half to death," she told a newspaper. "But I was so anxious to be with my husband that I resolved to see the thing through if it killed me." It did not, and fellow troopers simply assumed that Lindley and the "young man" known as Jim Smith were just good friends. Then there was Charlotte Hope, who signed up in the 1st Virginia Cavalry to avenge the death of her fiancé, killed in a raid in 1861. Her goal: to slay 21 Yankees, one for each year of her beau’s life.

Some joined to escape the misery of prostitution or destitution—a common problem with so few jobs open to women. Finance clearly figured into the decision of Sarah Rosetta Wakeman, alias Pvt. Lyons Wakeman, to sign up for the Union army. "I got 100 and 52$ in money," she wrote proudly. "I can get all the money I want."

Loreta Velazquez, a.k.a. Lt. Harry T. Buford, was one of several women who fought simply for the unadulterated thrill of it: "I plunged into adventure for the love of the thing," she said after writing a postwar memoir called The Woman in Battle. Many women felt the keen tug of patriotism. Union soldier Sarah Edmonds, an immigrant from Canada, expressed thanks that she was "permitted in this hour of my adopted country’s need to express a tithe of the gratitude which I feel toward the people of the Northern States."

"What surprised me most was the realization that women soldiers enlisted largely for the very same reasons as the men did," says Blanton, 38. "Some were rebelling against the strict roles that society confined them in, but then there were women who went because the pay was good, or because everybody else in the family was signing up, or because they wanted to defend their country. Some just signed up to run away from home, just like so many boys did."

To get to the front lines, each woman had to pass herself off as a man. Many were detected immediately and given the boot. But physical exams of the time tended to be cursory, and both armies were often so desperate for recruits that virtually anyone could pass. Occasions for discovery were limited; troops routinely slept in uniform, baths were a novelty and latrines were so foul that many soldiers sought refuge in nearby woods. A high-pitched voice or a lack of facial hair could be attributed to youth. Several women attempted to blend in by learning to cuss like sailors, taking up gambling, or even dating local young ladies.

Some female combatants were given away by ladylike mannerisms and others were undone by boastings while inebriated. But as with Clark, most were unveiled only when doctors stripped away their clothes to examine a war wound.

A native of Grand Rapids, Michigan, Cook had virtually no interest in the Civil War until 1987, when she toured the battle site at Gettysburg, Pennsylvania. She was so moved by the experience that she joined a fife and drum corps and began participating in battle reenactments. Then, in 1989, during a re-creation of a military hospital at the Antietam National Battlefield in Sharpsburg, Maryland, she dressed as a male soldier "because I felt that was historically accurate." But when she visited the ladies’ room, she caused a stir—not only among the women inside but with a ranger, who brusquely informed her that park rules did not allow women to participate in reenactments. "Their attitude was that the women of that era must have been oddballs, eccentrics and crazy, and didn’t merit any kind of recognition or respect," says Cook. Her lawsuit against the Department of the Interior ultimately changed the rules.

The lawsuit also brought Cook to the attention of Blanton, a senior military archivist at the National Archives, whose own curiosity had been piqued in 1991 when she chanced upon a small file about women who fought in the Civil War. "I had read of [Cook’s] difficulties with great interest and thought, 'You go, girl.'"

A decade after teaming up to work on Demons, Cook and Blanton are still fitting pieces of the puzzle. They cite the case, as it unfolded in letters written by soldiers, of a New Jersey woman who participated in the Union army’s June 1862 siege of Richmond, Virginia, was wounded at the Battle of Antietam in September, and fought in the Union defeat at Fredericksburg in December. Just a few weeks later, on January 19, an astonished colonel in the Army of the Potomac wrote home: "A corporal was promoted to sergeant for gallant conduct at the battle of Fredericksburg—since which time the sergeant has become the mother of a child."

And there the story stops. "When she and her baby went home, was she celebrated or shunned?" Blanton asks. "I hope that a descendant will read our book and call up and say, 'Hey, that lady was my great-great-great-grandmother.'"