Describe the reasons for the changes in Lincoln’s thinking with the progression of the Civil War. It initially focused on preserving the Union...

Lincoln's goal was first and foremost to preserve the Union.  He did not want to come out too strong against slavery because this would cause the border states—Missouri, Kentucky, Maryland, and Delaware—to secede and join the Confederacy.  Lincoln realized that if Maryland joined the Confederacy, Washington, DC, would be surrounded, and the war would be over.  As the war progressed, Lincoln initially thought it acceptable if armies in the field freed the slaves of secessionists...

Lincoln's goal was first and foremost to preserve the Union.  He did not want to come out too strong against slavery because this would cause the border states—Missouri, Kentucky, Maryland, and Delaware—to secede and join the Confederacy.  Lincoln realized that if Maryland joined the Confederacy, Washington, DC, would be surrounded, and the war would be over.  As the war progressed, Lincoln initially thought it acceptable if armies in the field freed the slaves of secessionists and claimed the newly freed people as "contraband" in war.  Lincoln issued his Emancipation Proclamation on January 1, 1863 in order to demonstrate that he was in control over the "states in rebellion," as this law did not cover slaves living in loyal states.  Lincoln hoped that such a move would scare hardened slaveowners back into the Unionist fold, but he had no such luck.  Another reason for this decree was that it gave the war a higher cause— now Britain and France would hopefully not agitate for mediation between the two warring factions.  Lincoln finally relented and put African Americans into active combat roles at the behest of Frederick Douglass, who thought that this was the only way for African American to achieve any semblance of equality after the war.  Lincoln did not believe that the former slaves would get a fair chance in the United States after the war, so he wanted to create a colony in the Western Hemisphere for them similar to Liberia.  Frederick Douglass and other black leaders talked him out of this.  The valor of black soldiers in battles such as The Crater and Fort Wagner also demonstrated to Lincoln that black soldiers were just as capable as white soldiers.  After the war, Lincoln saw that freeing all the slaves was the right thing to do, and it would also galvanize his party's abolitionist core to go along with him on other parts of his large domestic agenda to get the nation together.  Lincoln was a man of his time, and he did not quickly embrace civil rights. However, he was starting to become more accepting right before his untimely assassination.