In early September of 1862 General Lee decided to advance his army north towards Pennsylvania after the victory at Manassas. He could not provide enough supplies for his army to stay in their location. Lee hoped to engage in the final battle that would assure Southern Independence. He thought the north was weak and demoralized which made Lee confident of a victory.
Lee made a mistake that could have caused his entire army to be destroyed. On September 5th, his army moved into Maryland where he split his forces and sent Jackson along with ten-thousand soldiers to capture the garrison at Harpers Ferry. A copy of Lee's plans fell into McClellan's hands which gave him a sizable advantage.
McClellan followed Lee's army westward into Boonsboro. A stretch of mountains separated the two armies from each other. Since there were only a few passage ways through the mountains, they gave a great advantage to whomever controlled them. After two battles, the Turner Gap and the Crampton Gab were both seized by the unionists. This proposed problems for the Confederates because they could not cross the mountains. Lee thought of retreating back into Virginia, but Jackson quickly defeated the Union garrison at Harpers Ferry. The victory convinced Lee to make a stand against the north at Antietam.
On September 15th, Lee moved his army behind the Antietam Creek. This was a risky position for the Confederate soldiers, because if they began to lose then they would have nowhere to retreat. That night, McClellan arrived on the other side of the Creek with his army. Lee was lucky that the Union soldiers did not attack right away because his forces were still split. Both forces remained where they were for the entire next day while McClellan organized his troops. The battle broke out on the 17th, which turned out to be the bloodiest day of the civil war and in the history of the United States.
When the battle began the Union troops outnumbered the Confederates three to one. McClellan sent less than two-thirds of his men to fight Lee's entire force which made the odds fairly even. The fighting began with an attack on General Lee's left flank by Hookers corps. Attacks and counterattacks were led both ways across Miller's cornfield. The Confederates fought hard, forcing the Union Army to briefly retreat. Another attack was soon formed by McClellan's troops, but when they reached Dunker's Church the northerners were warded off by strong Confederate fire. As soon as the fighting died down a second battle began when the Union soldiers attacked the Confederate center. The strategic placement of Confederate soldiers in the sunken road soon became a deathtrap when McClellan's Army progressed. The southern troops got caught in the deep trench of the road. The union was doing so well in the battle that they could have broken through Confederate lines, but the attack died off. A third battle had started as McClellan's soldiers fought their way across the lower bridge of Antietam Creek. Union soldiers were clearly at advantage and made their way towards Sharpsburg until the AP Hills division arrived from Harpers Ferry. The Confederate to Unionist ratio increased and Lee's army successfully counterattacked. Since the day was coming to an end, both sides retired for the night. Neither side had won because General Lee had held off an army that was significantly larger than his. Though, the war could have ended if McClellan had not been so hesitant about using all of his troops. Later, this became the reason for his replacement by Ambrose Burnside. The Union had lost close to a thousand more soldiers than the Confederacy, but Lee retreated into Virginia. He had lost about half his army and could not risk anymore lives.
There were 12,410 Federal loses and 11,172 Confederate men killed, wounded, or declared missing. It was the bloodiest battle and yet neither side had a decisive victory. Though, it was a turning point for Lincoln, the Unionist soldiers, and the abolishment of slavery. Lincoln would not issue the emancipation of all African-Americans until the union was winning the war. He was afraid of being seen as diverting the attention from the defeats on the battle field. The north did not defeat the Confederates at Antietam, but Lincoln ruled it a victory because the south retreated into Virginia. The declared victory led Lincoln to believe that freeing all slaves would not lose him any support, so he issued the preliminary Emancipation Proclamation. He confirmed that on January 1st, 1863, "slaves wholly or partially in rebellion would be free."
