How did they find out that Deborah Sampson was a woman?

Answer 1

Deberah kept asking Samson what the secret of his power was, and he told her multiple times false secrets. After she cried before him and accused him of not loving her, he told her that hi secret was his long hair. She then told the philistines and they cut his hair.

Answer 2

They figured it out when A bullet wound she treated herself jn her leg didn't heal correctly and she fell sick with a high fever. They brought her to be treated in Philadelphia and the doctor undressed her to treat her and he found the band she used to bound her breasts to resemble a male physique.[she told her regiment that she was a young boy named Robert Shurtleff] the doctor didn't utter a word to anyone but acted in a respectful manner. He sent her to his house where she was treated by his wife and daughter. Instead when she was healed he sent her back with a letter to give to General Henry Knoxx and she was dreading that it was revealing her secret. Instead it was advice and to give her a sum of money when she left the army. She was released with an honorable discharge as she marched next to General Henry Knoxx as lowered muskets were lifted and fired.