First of all, the civil wasn't fought to free the slaves. It was fought to save the union. The north took a dislike to the south's wealth and blamed it on the fact slavery afforded the south free labor. When the south wanted to secede, Lincoln made the decision to go to war to keep the country whole. The side effect was the ending of slavery. The truth is the civil war was nothing more but the same old story time and time again through history. It was about money.
Lincoln's Letter to Horace Greeley
http://www.classicallibrary.org/lincoln/greeley.htm
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. What I do about slavery, and the colored race, I do because I believe it helps to save the Union; and what I forbear, I forbear because I do not believe it would help to save the Union.
Lincoln's Letter to Horace Greeley
http://www.classicallibrary.org/lincoln/greeley.htm