The significance of the Emancipation Proclamation during the U.S. Civil War lies in its legal assertion that all enslaved people in the Confederate states were to be set free. Issued by President Lincoln in 1863, it not only aimed to weaken the Confederacy's war efforts by depriving them of labor but also transformed the conflict into a moral crusade against slavery. This act paved the way for the eventual abolition of slavery with the 13th Amendment and added a new impetus for African American soldiers to enlist in the Union Army, granting them a stake in their own freedom.