Back in September, after the Union army had won the victory (or near victory) at Antietam, Abraham Lincoln had issued the Emancipation Proclamation. In it he said that the slaves in the states in rebellion would be freed if the states were still in rebellion on January 1st, 1863. That day had come, the war was still continuing, and so the Proclamation went into effect. However, only a small number of slaves were actually freed on this day. The Proclamation was declaring the slaves free in areas over which the government had no control, so until the armies pushed forward and recaptured the southern states, they would remain in slavery. However, there was a fraction of slaves that were immediately effected by the proclamation. The status of the “contraband of war,” slaves which had either escaped their masters or been released as the Union armies advanced, was made clear. They would be free. It appears that about 20,000 to 50,000 of the 4,000,000 slaves of the south were officially freed by this proclamation.
Not everyone in the north was pleased by this course of events. The war had begun as a fight to restore the Union. Although it was given as a war measure, Lincoln, with this proclamation, turned the purpose of the war to ending slavery. Many Northern Democrats disagreed with this measure, and some state legislatures even officially condemned Lincoln's course. However, the Republicans retained political power, so they would be the ones who would prosecute the war as they saw fit.