What was the main idea of the emancipation proclamation?

Lincoln Issues the Emancipation Proclamation. One month later, after the capable Union victory in the Battle of Antietam, Lincoln issued a prior proclamation ominous that in all states still in rebellion on January one eighteen sixty-three, he would declare their slaves then, thenceforward, and forever free.

Delaware, pennsylvania, new jersey, georgia, connecticut, massachusetts bay, maryland, south carolina, new hampshire, virginia, new york, north carolina, and rhode island and providence plantations where the 13 original colonies