Correction Appended













One day Ms. Cook received a letter from Ruth Goodier of Chipley, Fla. Ms. Goodier said she had heard of Ms. Cook's lawsuit and supported her right to serve as a male soldier during re-enactments. She added that she knew women had fought in the war because her great-grandmother's older sister, Sarah Rosetta Wakeman, had served two years, and that she had a collection of Wakeman's letters home from the front. She also had a daguerreotype of Wakeman, dressed in her uniform, holding her musket with the bayonet attached, that had remained hidden in a family attic for years.

Ms. Cook was astounded, since no collection of letters written by female soldiers was known to exist. In the hope of getting the letters published, she started researching the life of Wakeman, who used the name Lyons Wakeman while serving in the 153rd New York Volunteer Infantry. Wakeman saw action around Washington and in the 1864 Louisiana Red River campaign before dying that year in an Army hospital from the effects of chronic diarrhea. Oxford University Press published the Wakeman letters, edited and annotated by Ms. Cook, in a 1994 book entitled ''An Uncommon Soldier.''

It was while researching the Wakeman letters at the National Archives that Ms. Cook and Ms. Blanton met and talked about pooling their resources and writing a book together about female soldiers. In the beginning, they simply set out to document as many as they could find. This alone was a challenge, as many of the women came from working-class backgrounds and couldn't write. Others went home after the war, married and had children, and, not wanting to seem different, never talked about their war experiences. But Ms. Blanton and Ms. Cook quickly realized that they didn't want just to tell the stories of the individual women who had served. They also wanted to set them in a context, to explore how the women fit into the broader society.

''One of the things that bothered me when I was asked to leave the Antietam battlefield after portraying a male soldier was the attitude of the park officials there,'' Ms. Cook recalled. ''They considered Civil War women soldiers eccentrics and oddballs, that something wasn't quite right about them.''

In fact, as the two women delved more deeply into how Civil War society viewed these soldiers, they were astonished to discover that, although politicians and pundits were often critical, male soldiers usually accepted their female comrades once they were unmasked. Women who were quickly discovered in the ranks and dismissed went home in disgrace, but those who managed to keep their secret for a time and serve in battle found that their fellow soldiers supported them even after their identities became known. In letters home and in wartime diaries, male soldiers praised the bravery and military prowess of the women who served with them and in many cases kept the women's identities a secret from their officers so that the women could continue to serve.

''What surprised me the most is that these women did something so unacceptable to society at that time, but they were so accepted by the men they served in the ranks with,'' Ms. Blanton says. ''It was war, and on the battlefield people couldn't afford to indulge in social conventions.''

Ms. Blanton and Ms. Cook found that especially true on the Confederate side, where manpower was short and officers were desperate to keep the ranks filled as the war dragged on. By 1864 many of the Confederate female soldiers weren't even pretending to be men anymore. They were growing their hair long again and no longer trying to conceal their figures.

For Ms. Cook, whose journey into the world of female soldiers started when she was sent home from the re-enacted battle, this was the best discovery of all. That and the evidence from their research that eight women had served disguised as male soldiers at the battle of Antietam, the highest number they documented at any one battle. Five of the eight were casualties that day.

Photos: Lauren M. Cook, co-author of ''They Fought Like Demons,'' a forthcoming book on female soldiers in the Civil War. (Jesse Shaw); Sarah Rosetta Wakeman, who served in the Union Army disguised as a man. (pg. B7); Lauren M. Cook, who sued for the right to take part in Civil War re-enactments, dressed in a federal uniform for a mock battle in 1992. (Gilbert Faust)(pg. B9)