The slaves in the South freed themselves from slavery. Abraham Lincoln’s intention of the Civil War was to bring the Confederacy back into the Union and he did not have to end slavery to preserve the Union. During the war, Lincoln established the Emancipation Proclamation that declared the slaves free, but the slaves had to make their own decision to escape from the South. Lincoln only encouraged the slaves to free themselves, not physically moving them into the Union.
From www.pbs.org/wgbh/aia/part4/4p2967.html, “...it was a war to preserve the Union. His words were not simply aimed at the loyal southern states..” This conveys Lincoln’s main objective during the Civil War was to save the Union as a whole, not to end