The Emancipation Proclamation changed the focus of the war.

Up until September 1862, the main focus of the war had been to preserve the Union. At the level of principle, the goals of the American Revolution were outlined in the Declaration of Independence of 1776. More specifically, patriots fought the revolution in order to: 1) become an independent nation; 2) create a new system of self-governance; 3) claim equal rights for all citizens and establish the rule of law required for that to be meaningful; 4) gain independent membership in the European state system; and 5) rid themselves of tyranny. The revolutionaries’ goal was to create a viable nation-state that would be equal in standing to the nations of Europe. Patriots expected that an independent America would assume a “separate and equal station” among other modern European nations, including France, the Dutch Republic, Spain, or even Britain and worked actively to bring that about. Despite stating that one of the main focuses of the war was to claim equal rights for all citizens, the freedom of slaves was never in question.

That is until the issuance of the Emancipation Proclamation in which President Abraham Lincoln stated "the Executive Government of the United States, including the military and naval authority thereof, will recognize and maintain the freedom of such persons, and will do no act or acts to repress such persons, or any of them, in any efforts they may make for their actual freedom" while mentioning one of the goals that the war aims for. Thanks to that, freedom for slaves became a legitimate war aim, and by the end of the war, many slaves earns their freedom.