In 1863, during the Civil War that had torn the United States apart, President Abraham Lincoln signed the Emancipation Proclamation, which declared that all slaves would be freed in the Confederate states at war. Considered Lincoln's most direct action to hasten the end of slavery, the proclamation promised that slavery would effectively end at the conclusion of the war - and also allowed African Americans to serve in the Union army. Though the Emancipation Proclamation could not be enforced in the Confederate states until after the war, its issuance linked the Union's fight for the country's unity with the moral cause of freeing the slaves. In ""The Emancipation Proclamation"", read about the groundbreaking document that was a precursor to the 13th Amendment to the Constitution that effectively ended slavery in the United States.