For Women’s History Month, Atlas Obscura delves into the world of espionage, where being overlooked and underestimated has been an asset for centuries of women spies. Previously: The Invisible, Afflicted Spy Who Led the U.S. Army Into Occupied Manila. The pretty young woman with the dark curls was searching for her lost brother. That wasn’t unusual in the summer of 1863. The American Civil War had been raging for two years. Hundreds of thousands had died and the chaos of ongoing battles meant that family members on both sides of…