The firefly (1937)

Nina Maria Azara is the beautiful and alluring singing spy for Spain during the Napoleonic Wars. Her mission is to seduce French officers, in order for them to reveal Napoleon's intentions toward Spain. She is sent to Bayonne, France to gather military secrets. Prior to this, she meets Don Diego while performing at a club. Unknown to her, Don Diego is actually Captain Andre, who is sent to Spain to spy on her. While in France, Nina discovers Diego's true identity, only after she has fallen in love with him. Nina Maria outwits her potential captors, returns to Spain and goes into hiding. Napoleon's troops invade Spain, resulting in Nina's capture. In a strange twist of fate, Nina and Captain Andre are reunited, but the 2 nations are now at war...