The Civil War began more as a battle over the preservation of the Union than as a battle over slavery. Many felt that the real issue at stake was the question of states’ rights versus federal power—whether states could secede from the Union in protest against federal policy, regardless of whether that policy concerned slavery or another issue, such as tariffs. Slavery was therefore considered the catalyst for the nation’s rupture, but not the primary cause. It was not until Lincoln’s Emancipation Proclamation that slavery emerged as the central issue at stake.

In the East, the Union Army aimed to capture the Confederate capital of Richmond, Virginia. Most of the early battles ended in stalemate, with both sides suffering devastating losses. After a Southern victory in June 1862, Confederate general Robert E. Lee led his forces on a powerful march northward from Virginia, aiming to break Union lines. What followed, in September 17, 1862, was the bloodiest single-day battle in the Civil War: the Battle of Antietam, in which more than 8,000 men died on the field and 18,000 were wounded. Though a strategic draw, the battle proved a Union victory in that Lee halted his Confederate advance northward. Lincoln responded to this victory by issuing the Emancipation Proclamation.

General Lee struck northward into Pennsylvania in July 1863, but was again blocked by a strong Union defense. In the three-day Battle of Gettysburg, 90,000 Union soldiers battled 75,000 Confederates and secured a Union victory. The losses were ruinous to both sides: a total of 7,000 soldiers died on the field and 40,000 were wounded. Although fighting would continue for more than a year after the Battle of Gettysburg, the battle proved a decisive victory for the Union, and the war thereafter tilted in the Union’s favor. Later that year, Lincoln delivered his famed Gettysburg Address, in which he portrayed the war as a test of democracy’s strength.

In the West, the Union experienced successes much earlier on. Led by General Ulysses S. Grant, the Union secured control of the Mississippi River and moved southward. At the Battle of Shiloh, in April 1862, Grant’s troops were ambushed by Confederates, but Grant proved victorious. Both sides suffered heavy losses, as nearly one-third of the 77,000 men involved were killed.

Early in the war, Union officials were uncertain how to treat Southern slaves who fled to the North or were captured by the army. Lincoln was cautious in his approach to this matter, since the Union contained four slave states and many pro-slavery Democrats. He vaguely supported the policy of confiscation, in which slaves who had worked for the Confederate military were considered captives of war and put to work for the Union army. Each Union loss in the war, however, made emancipation a more attractive recourse, since slave labor drove the Southern economy and allowed the Confederacy to devote more white men to war. Lincoln eventually came to favor emancipation, and only awaited the right moment to announce his decision.

After the Union victory at Antietam in September 1862, Lincoln issued the Preliminary Emancipation Proclamation, declaring all slaves under rebel control free as of January 1, 1863. The final Emancipation Proclamation was issued on January 1. In practice, the Proclamation freed very few slaves because it did not affect the slave states within the Union or the parts of the Confederacy under Union control. But as a political move, it proved decisive and brilliant. The proclamation mobilized the support of European liberals (Great Britain and France had outlawed slavery earlier in the century), and it appeased the Radical Republicans in Congress. Abolishing slavery thus became one of the Union’s primary objectives for war, along with preserving the Union.

The Emancipation Proclamation did significantly affect the war by bolstering the Union’s forces. After the Proclamation, the Union began to enlist black soldiers in conquered areas of the South. In all, almost 200,000 blacks enlisted. By the end of the war, black soldiers comprised almost one-tenth of the Union Army. Although blacks were paid less than whites and assigned to less desirable posts, their military service was an important symbol of black citizenship.

In early 1864, Lincoln appointed General Ulysses S. Grant commander of all Union armies. The string of Union victories that followed that summer, especially General William T. Sherman’s victories in Georgia, helped Lincoln win reelection in 1864. Union forces continued to rout the Confederate Army after Lincoln’s reelection, destroying much of Georgia and South Carolina in what is known as Sherman’s March to the Sea: Sherman and his troops first burned Atlanta, and then marched toward the coast, demolishing everything in their way, including railroads and factories. Sherman estimated that his forces ruined $100 million worth of property.

One month after Sherman’s forces conquered Charleston, South Carolina, Grant took the Confederacy capital in Richmond, Virginia. Robert E. Lee’s forces officially surrendered to Grant on April 9, 1865. One month later, Confederacy President Jefferson Davis was captured in Georgia.