Emancipation Proclamation was meant as much to deal a strategic blow to the confederacy as anything else. It gave the Union the moral high ground in the war on the international stage. If a nation such as Britain, which worked actively to outlaw slavery, wanted to assist the South, they would have to acknowledge that they were helping to defend slavery.

At the same time, the complete abolition of slavery was far from a reality in 1863. The Union didn't want to do too much to anger slave states that stayed loyal such as Missouri and Maryland, or recently passified territories.

It was not until two years later with the passage of the 13th amendment that slavery was abolished in all of the United States.