La hija del regimiento (1944)

In a fictional country, a colonel has a daughter, but unknowingly to him she is switched for a boy. The girl is left at a military headquarter, where she is adopted by the army and raised as their own. In her 20th birthday she is accepted as a corporal despite the prohibition for women to join the military, and the soldiers try to hide her identity when they are visited by a officer, the boy that the colonel raised as his own.