I think you will find this article from the Internet very interesting as to what happened on August 22, 1862 (150 years ago today)
Friday Aug. 22 1862
PRESIDENT PREACHES TO PROLIFIC PRESSMAN

Three days ago Horace Greely, writing in his New York Tribune, had published his classic “Prayer of Twenty Million”, imploring Abraham Lincoln to make the abolition of slavery the main aim of the current war. Today Lincoln responded with a statement so clear even a newspaperman should have understood it: “I would save the Union. I would save it the shortest way under the Constitution.. …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.”
Guess the victors write the history books. How many people know Lincoln said this?