What would possess a girl to dress up and pose as a boy? As the following books will tell you, there’s plenty!
Some choose to do so to hide from people who wish them dead. Posing as a boy would be able to confuse the enemy who wants to track her down. And in cases where she is left alone in an environment that preys on the weak, being a boy would lessen (at least in some small part) the perceived vulnerability.
For others, it’s not as much hiding as it is a way to gain an opportunity closed to her if she “remains” a girl. This is very popular especially in fiction that shows culture wherein the females are simply relegated to the home and care of children. Some girls dress up as boys in order to avail themselves of education and/or the chance for adventure in the outside world.
What I see in common in books that make use of this trope is how being female is seen as a weakness. At least at the start of the book. In order for the main female character to be treated seriously, she has to deceive others into thinking she’s a boy despite the fact that her achievements have little to do with gender but more to do with her hard work and will to succeed.
But what I like is that these books is that the main characters do not totally eschew their gender. They don’t hate themselves for being born a girl. They do not think being a girl is inferior to being a man. Yes, they are female. But they have accomplished great things equal to those accomplished by a man.
Eventually, their masquerade does get found out. And I like that these ladies can take away from this the knowledge that they are capable and strong. And that their gender is not a hindrance to doing great things.