In 1862, the American Civil War was raging on. The war had started in 1861 after the election of President Abraham Lincoln. Lincoln was against slavery while the southern states supported slavery. So when he was elected, the southern states broke away from the Union and formed their own government called the Confederacy. The northern states responded by forming the Union and both sides declared war on each other.
Before the Battle of Antietam, the Confederate army had defeated a large Union army in the Second Battle of Bull Run. This increased the morale of the Confederate army and it decided to attack the Union army by crossing into Union-controlled territory. So a Confederate army under General Robert E. Lee entered the state of Pennsylvania.
The battle took place near Washington County of Maryland. It took place on September 17, 1862.
The Union army was led by General George B. McClellan. The Confederate army was led by General Robert E. Lee. The total number of the Union army was around 85,000 while the Confederate army was much smaller, having only 38,000 soldiers. This numerical disadvantage proved significant in the battle.
The fighting began when a portion of the Union army led by General Joseph Hooker attacked the Confederate army. Although the Union army was more than twice the size of the Confederate army, General McClellan was unwilling to use the entire army in the battle. So only a part of the Union army actually fought in this battle.
The Confederate army had to face repeated attacks from the Union army but it also counter-attacked many times. General Robert E. Lee continuously shifted Confederate soldiers from one position to another, successfully countering all Union attacks and at the end of the day, the Confederate line of defense still stood despite a huge number of casualties. By the end of September 17, neither side had won.
The next day, the Confederate army continued to fight small skirmishes with the Union army but at the same time, it began to retreat back to Virginia and leave the state of Pennsylvania.
On the battlefield, it was a draw. Neither side was able to push the other from the battlefield. But more generally, this was a defeat for the Confederate army. The Confederate army had entered Pennsylvania with the aim of gaining control of the state but it was immediately forced back to Virginia. This was one of the deadliest battles of the Civil War. The Union army suffered 2,000 dead with nearly 12,000 casualties. The Confederate army suffered nearly 1500 dead with 10,000 casualties.
At the time, the Confederate government was hoping that a victory by the Confederate army would persuade Britain and France to support the Confederacy. But these hopes were dashed when General Lee’s Confederate army lost the battle. On the other hand, President Abraham Lincoln used this opportunity to announce the famous Emancipation Proclamation which offered freedom to all the slaves in the southern states.