Responses
The story description bears similarities to "The Villainess's Blind Date Is Too Perfect", where a female lead disguises herself as a man to become a knight and meets a duke on a battlefield.
Another potential match is "Undercover Empress", which features a female lead cross-dressing as a man in a military setting.
The description of a silver-haired girl disguising herself as a boy is common in the otome isekai genre, similar to characters in "I Choose the Emperor Ending".
Google gave this
It’s about a girl disguise as a boy. I remember a handsome duke or something pick her up at a battlefield after some war. Her hair is white or silver. She lied about her family background and begged to the duke to take her.