Antietam

By September 1862, the Union position was grave.  Lee had manhandled Union armies, Maryland's support for Lincoln's cause was cooling and Great Britain was threatening to recongnize the Confederacy - perhaps even use the powerful British navy to break the Union blockade of the South.  Lincoln needed a victory badly.

Knowing the stakes were high, and that another victory might tip the balance heavily in favor of the Confederacy, Lee decided to invade Maryland.  He crossed the Potomac and camped near Frederick.  There he issued orders to divide his force and gave instructions to his commanders to concentrate near Sharpsburg, along the Antietam creek.  McClellan, in command again, kept his much larger army between Lee and Washington, and moved slowly west toward the rebels. 

Then a stroke of luck - a Union officer found Lee's orders in a field near Frederick wrapped around cigars.  A rebel officer had carelessly dropped them while in camp.  McClellan now had the key to defeating Lee, since the orders revealed that the rebel forces were divided, and gave details on the routes to be taken by each of the Confederate corps. 

Lee's army was arrayed along the Antietam Creek east of Sharpsburg MD and McClellan moved into position to attack.  Lee urgently called all of his forces to oppose the Union army.  On the morning of September 17, 1862, the 75th anniversiary of the Constitution, the battle opened.  The two armies battered each other all day, with the rebels falling back then holding all along the line.  By day's end, the positions were nearly the same as morning, except for the carnage.

Antietam is the bloodiest day in American history.  More than 23,000 casualties were suffered by both armies, more than the US on D-Day.  Both sides had suffered equally, but McClellan still had large fresh forces to attack, and Lincoln urged him to destroy Lee's army.  Next morning, the attack Lee expected never came, McClellan being an inordinately cautious field commander.  Lee escaped across the Potomac.

Lincoln had a victory at last against Lee, and decided to issue the Emancipation Proclamation.  The British backed away from supporting the Confederacy.  And Maryland confirmed Union support.

Yet, by failing to destroy Lee's battered army the next day, McClellan missed a chance to end the war, and avoid the killing of another 400,000 Americans in the next 30 months of war.