One of the most deadly battlesMcClellan decided to begin hostilities on September 17.At that time, Lee’s forces, estimated to have 45,000 combatants but limited to 30,000 men at the beginning of the engagement, were arranged in an arc around Sharpsburg, on a front of about 5 kilometers. The right and center were held by the reinforced Longstreet Corps of the DH Hill division; the left was held by Jackson’s reinforced body of Stuart’s cavalry.In the northern camp, McClellan had 60,000 men and expected 12,000 reinforcement in the morning. With other more distant troops, he could hope to have a maximum of 87,000 soldiers, a superiority of two against one.
It also had a strong artillery, firepower incomparably more powerful than that of the Southerners.On the northern right wing, two army corps, those of Generals Hooker and Mansfield, had managed to cross Antietam Creek and threatened the southern left. The center and the left northerner were east of Antietam Creek and consisted of General Sumner’s body (waiting to be reinforced by Franklin’s) and, on the left facing a bridge over the brook, to that of General Bunrside. McClellan had been able to afford the luxury of keeping an entire body, that of General Porter, in reserve.McClellan’s plan was to launch a major attack on the southern left and a diversion attack on the right. By the time Lee’s forces were quite worn out, he would have triggered the decisive attack in the center, involving all the reserves.
The first operationsThe Southern advance was rapid, and on September 7, 1862, General Lee’s North Virginia Army reached the principal city of Frederick. There, Lee made a proclamation inviting the state to join the Confederation but, in the conquered territories, the reception was freezing.At the same time, Lee turned his attention to the nearby Harpers Ferry, a major arms production center, which was held by a small contingent of northerners capable of threatening his rear in his later progress.
Once again, Lee took the risk of dividing his army of 45,000 men and entrusted part of it to General Jackson with instructions to seize Harpers Ferry. He split his army again and entrusted part of it to General Longstreet, who was tasked with seizing the South Mountain passes to the north-west.In the northern camp, the cautious but brilliant organizer McClellan had been reinstated at the head of the armies of the Eastern treasure. McClellan put an end to the existence of Pope’s Army of Virginia and integrated his forces into his Potomac army, with 90,000 combatants.
Reassured by his numerical superiority, McClellan went on the counterattack as early as September 8th.
Four days later, small numbers of northerners came into contact with small southern contingents in the Frederick area. Skirmishes arose but, crucially, a northerner found in an abandoned tent a copy of Lee’s plan describing the subdivisions of his army and the march from Jackson to Harpers Ferry.McClellan exulted and, for the first time, forgot all his caution. He decided to send forces to South Mountain, a relief column at Harpers Ferry, and launch the rest of his army on Lee’s main force, now weak.
“Hunt the natural, it comes back at a gallop,” they say. When the first clashes began in the South Mountain area, McClellan was cautious again and estimated that Longstreet’s southern forces were twice as large as they actually were. A decisive northern assault would no doubt have led to the destruction of Longstreet, but McClellan remained silent and the southern general, recalled to Lee now aware of a massive northern presence, was able to clear himself easily.
All southern forces converged on the locality of Sharpsburg, ten kilometers to the west, and stood at the shelter of the small stream of Antietam Creek. Jackson, who had just seized Harpers Ferry, taking 12,000 northern prisoners and large quantities of weapons (13,000 rifles, 73 pieces of artillery, …), returned forced to Sharpsburg where Lee was waiting the massive northern assault by having only half of his army. Jackson, however, was forced to leave Harpers Ferry with the division of General Ambose Powell Hill, who was charged with settling the city’s formalities for surrender. Everyone was unaware then that this small troop would play a crucial role in the major battle ahead.Fortunately for Lee, McClellan maneuvered with the utmost caution and slowness. The days of September 15 and 16 saw the northern army observe the positions of Lee but limited to some artillery fire as a single offensive action.
>In September 1862, following the second Bull Run battle , the southern authorities changed their strategy. Abandoning the idea of fighting for its own defense, the Confederation decided to carry the war into northern territory and, more specifically, into the border state of Maryland.
This invasion could have several advantages :
- Maryland, whose population was culturally close to that of the southern states, could perhaps rally to Confederation
- seeing itself invaded, the North, whose morale was at its lowest, might be forced to ask for peace
- in the case of an important confederate victory in northern territory, one could assume that some European powers would recognize the Southern cause as legitimate
- practically, Confederate stewardship, inefficient, could be provided on a rich territory, until then spared by the destruction.
The Southern army began the invasion of the North on September 5, 1862, crossing the Potomac at Leechburg.