One wartime order redefined the Civil War as a fight to end slavery

On 1 January 1863, Abraham Lincoln's Emancipation Proclamation declared enslaved people in Confederate-held territory 'forever free.' It freed no one directly, since it only applied to areas outside Union control, but it transformed the Civil War's purpose, opened the Union Army to Black soldiers, and set the stage for the 13th Amendment's permanent abolition of slavery in 1865.

— Wikipedia contributors, Emancipation Proclamation — 1 January 1863