Women that wanted to fight in the war, cross-dressed to help out. Some wanted to fight because they were lonely, while others had a strong sense of nationalism
each army was constantly looking for new recruits, but had little restrictions as to who they were. Women obviously were not supposed to be on the battlefield but 400 women defied those standards.
Generals on both sides didn't want women fighting for them. They believed they were not as capable as men. However, the undercover women had the exact same jobs as the men did like, being a spy, nurses, and they actually fought in the battles.
how did they do it? well since there were no other requirements that you must be 18, it was super easy for women to conform. Most soldiers look the same anyways, so most women cut their hair and made their voices deeper when talking to others and no one suspected a thing.
the women that got caught didn't face that bad of a punishment. they were only imprisoned for a short period of time.
ultimately the women that disguised themselves were extremely courageous