The main effect of the Emancipation Proclamation on the Civil War was that it transformed the conflict from a battle for the Union to a struggle for freedom. Issued by President Abraham Lincoln in 1863, it declared the freedom of all enslaved people in Confederate-held territory, which aimed to weaken the South's war effort and bolster the Union Army by allowing for the enlistment of freed slaves. This shifted the war's moral focus, making the abolition of slavery an explicit goal and contributing to the eventual passage of the Thirteenth Amendment, which abolished slavery in the United States.