Emancipation Proclamation (1863)
Historians say that the Emancipation Proclamation added moral force to the Union cause and transformed the Civil War from a war to save the Union into a war for freedom, justice, and equality. Further, the statement that slaves were to be freed may have prevented the British from entering the war on the side of the Confederacy.
Because the President believed that he lacked the constitutional authority to free slaves, Lincoln issued this document as a war measure in his capacity as Commander-in-Chief of the military. Freed slaves were welcomed into the armed forces. The proclamation did not affect slaves in states that had not seceded from the Union. It also exempted from its provisions some sections of rebelling states that were already under Union control.
Years later in 1865, the question of slavery would be settled once and for all with the ratification of the Thirteenth Amendment.