What were Lincoln’s motives in deciding for general emancipation? The emancipation itself changed the nature of the war. It reflected a fundamental change in Lincoln’s own thinking about the relationship of slavery to the war as well as the future place of blacks in American life. The point is not that Lincoln freed four million slaves with a stroke of the pen, but that the Proclamation was a key moment in the complex and prolonged historical process that led to the end of slavery in the United States, with consequences to the present. 

Eric Foner is DeWitt Clinton Professor of History at Columbia University and a Past President of the American Historical Association. His books include Reconstruction: America's Unfinished Revolution, 1863-1877 (1988) and The Fiery Trial: Abraham Lincoln and American Slavery (2010).