The Civil War began in 1861 as a struggle over whether states had the right to leave the Union. President Abraham Lincoln firmly believed that a state did not have that right. And he declared war on the southern states that tried to leave.
But the fight to preserve the nation was going badly. By summer of 1862, Union troops had not won a decisive victory in Virginia, the heart of the Confederacy. And the war was losing support with politicians and the public in the north. President Lincoln had to do something to guarantee their continued support.
Finally, in September 1862, the Union successfully stopped the Confederate invasion of Maryland. The armies of Union general George McClellan and Confederate general Robert E. Lee battled near Antietam Creek. Almost 100,000 men fought. More than 23,000 were killed, wounded or missing.
Antietam was a violent, savage battle — the bloodiest one-day battle in American history. But the North’s victory there made it easier for Abraham Lincoln to make an important announcement.
Lincoln decided to recognize that slavery was, in fact, a major issue in the war. On September 22, 1862, he announced a new policy on slavery in the rebel southern states. His announcement became known as the Emancipation Proclamation.