Final answer:
President Abraham Lincoln's Emancipation Proclamation, issued on January 1, 1863, declared that slaves in rebelling states were free, transforming the Civil War into a fight against slavery and eventually leading to the enlistment of black soldiers, bolstering the Union's ranks and altering the course of the war.
Step-by-step explanation:
The Emancipation Proclamation was issued by President Abraham Lincoln after the Union victory at Antietam. Inspired by this small victory, Lincoln frees all slaves in the rebelling states on January 1, 1863. However, the proclamation specifically freed slaves only in areas still in rebellion against the United States, leaving over 700,000 slaves in bondage in Union border states and Union-occupied areas of the Confederacy.
The document wielded the President's war powers to declare enslaved individuals in the Confederacy to be free, while strategically leaving slavery untouched in sympathetic or occupied regions to prevent legal challenges and maintain political balance. The political move redefined the war, shifting its purpose towards the abolishment of slavery. Though immediate physical freedom did not come to all slaves due to lack of Union control in the South, the proclamation ultimately led to the enlistment of about 200,000 black soldiers, helping to turn the tide of the war in favor of the Union. Despite its limitations, the Emancipation Proclamation represented a monumental step in changing the character of the war and laid the groundwork for the eventual end of slavery, which would be solidified by the Thirteenth Amendment to the Constitution. The proclamation also had significant international repercussions, deterring British recognition of the Confederacy and signaling a moral stance that slavery would not persist in a reunited United States.