What's the background of Brady's photo?

Mathew Brady (1823 ~ 1896), a famous American portrait photographer, was the founder of "Daguerre-style small gallery" in America. He is convinced that only the camera is the highest recorder of history. During the American Civil War (186 1 ~ 1865), he entrusted the photo studio business in new york and Washington with a loan of $65,438+million to lead a "battlefield photography team" composed of 19 photographers to the battlefield to shoot various battles at the front. In four years, they filmed almost all the scenes of the war, and * * * obtained about 7,000 negatives, all of which were signed "Brady photos".