Abraham Lincoln:
"My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that."
Letter from Lincoln can be found here:
http://www.shotglassofhistory.com/abraham-lincoln-quote-slavery-civil-war/
Sourced: Collected Works of Abraham Lincoln, edited by Roy P. Basler et al.
You left the last part of the letter out;
“I have here stated my purpose according to my view of official duty; and I intend no modification of my oft-expressed personal wish that all men every where could be free.”
This belief put him morally above the leaders of the confederacy, and probably most Americans, of his day.