On September 22, 1862, President Lincoln issued the preliminary Emancipation Proclamation. He declared all slaves in the rebel Confederate States would be free if the those states did not rejoin the union by January 1, 1863.
The Confederate States refused to obey Lincoln's orders and the focus of the Civil War shifted from preserving the union to freeing the slaves.
President Lincoln issued the Emancipation Proclamation five days after the Battle of Antietam. Lincoln had planned to issue the proclamation much earlier, but the union had recently lost many battles to the Confederacy. He feared that issuing the proclamation earlier might seem like an act of desperation. After the union victory at Antietam, Lincoln knew the timing was right to strengthen the resolve of the union and change the course of the war.
The Emancipation Proclamation meant many different things to different people.
Abolitionists in the North saw the emancipation of slaves as a glorious victory. Southerners saw the proclamation as final proof that the Union was bent on destroying the southern way of life. Slaves in the south saw the Union troops as liberators, coming to free them from bondage.
By issuing the Emancipation Proclamation, northerners now had a real reason to fight. The proclamation gave strength to the efforts of Union troops, and President Lincoln made it clear that the Union's purpose was now to free the slaves.
The proclamation did not free slaves in the Confederate states immediately. As union troops captured territory in the south, more and more slaves were set free. Over time, the proclamation paved the way for full abolition of slavery across the United States.
The Emancipation Proclamation also allowed free blacks to enlist in the Union Army. Many free blacks from the north joined the cause to help free their enslaved brothers in the South.