Abraham Lincoln biggest objective in the Civil War was to

Its was to save the Union.

Explanation:

President Lincoln told a New York newspaper that preserving the Union was his main goal of the Civil War — not abolishing slavery. "If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all slaves I would do it," Lincoln said.

Not establishing Slavery

Explanation:

During the Civil War, Abraham Lincoln's biggest objective was not to establish  

slavery. Meaning that he had to give it his all to win the war against the Confederate States of America.

Hope this helps :)