How Did They Do It?
Women soldiers were more prevalent in the Civil War armies than anyone thought. The main reason being, they were dismissed by historians chronicling the era, because they were thought to be a rarity.
But the fact is, many more than thought sneaked into the ranks and this fact was only discovered years later by researchers reading diaries, letters, and journals of the period, as well as obituaries.
At the time of the Civil War, women were not allowed to serve as soldiers. Newspapers writers of the late nineteenth century grasped this point. "The actions of Civil War soldier-women flew in the face of mid-nineteenth century society's characterization of women as frail, subordinate, passive, and not interested in the public realm. http://www.archives.gov/publications/prologue/1993/spring/women-in-the-civil-war-3.html
But, how did all those women in disguise get into the armies in the first place?
Part of it had to do with the physical exam given to new recruits. The modesty of the Victorian era helped, as well as the many men swarming to join all at once. "In most cases, the physical examination was so hastily administered that most women had no problem passing and went on to fulfill their enlistment." http://www.geocities.com/yosemite/2518/cladinuniform.htm
Most didn't have to disrobe when undergoing the physical. Women who encountered a doctor who required this, would just decline to be examined and find another recruiter who they could slip by.
The estimated number of disguised women serving in the armies, was between 500 and 1000.
In most cases the medical exam consisted of "... holding out his hands to demonstrate that he had a working trigger finger, or perhaps opening his mouth to show that his teeth were strong enough to rip open a minie ball cartridge." All the Daring of the Soldier: Women In the Civil War Armies, p. 202
"... women soldiers picked male names. Army recruiters, both Northern and Southern, did not ask proof of identity. Soldier-women bound their breasts when necessary, padded the waists of their trousers, and cut their hair short. Loreta Velazquez wore a false mustache, developed a masculine gait, learned to smoke cigars, and padded her uniform coat to make herself look more muscular." http://www.archives.gov/publications/prologue/1993/spring/women-in-civil-war-3.html
Also Civil War armies didn't have anything resembling modern day bootcamp. The emphasis was on drill. "Many privates had never fired a gun before entering the army. The women soldiers learned to be warriors just like the men." http://www.archives.gov/publications/prologue/1993/spring/women-in-the-civil-war-3.html
That there were so many young men and even boys serving in the army, also helped women to avoid detection. Also the dress of the nineteenth century dictated that "... if it wore pants, it was male." All the Daring ... p. 205
As for taking care of personal needs, all a woman soldier had to do was claim modesty. She could take care of her needs in the woods away from prying eyes and no one would think anything of it. As for menstruation, a lot of researchers surmise that with all the hard physical activity of army life, most women would have stopped menstruating. If not, they could always hide the evidence after a battle among all the bloody bandages and clothing.
It seems the fact that no one expected women to be in the ranks, was what helped them to maintain their disguises for so long.
Sources: All the Daring of the Soldier: Women of the Civil War Armies by Elizabeth D. Leonard, pp. 199-225
In Part V, I'll talk about why they did it.