The main issue that Lincoln's presidency addressed during the Civil War was the preservation of the Union. As the nation faced a brutal internal conflict primarily over the issues of slavery and states' rights, Lincoln focused on maintaining national unity while navigating the profound moral and political complexities of the war. His Emancipation Proclamation in 1863 also aimed to weaken the Confederacy by freeing enslaved individuals in the rebellious states, making the fight against slavery a central goal of the war. Lincoln's leadership ultimately transformed the war into a struggle for freedom and equality.