On this date 149 years ago, the Union Army of the Potomac achieved victory in the first significant battle fought north of the Potomac River during the American Civil War. For an in depth narrative of the battle, I suggest The Battle of South Mountain by John Hoptak, which I can't recommend highly enough. It is an excellent and engaging narrative of the day's events, placing them within the larger strategic context of the campaign, some of which I will cover below.
Lee had come north into Maryland hoping for a victory which would have a wide ranging impact. The summer of 1862 had been one of many strategic and tactical victories for the Confederacy, and at Second Manassas in late August, Lee and his lieutenants Stonewall Jackson and James Longstreet had effectively destroyed John Pope's Army of Virginia. Coming north into Maryland and defeating another Union army offered the possibilities of bringing about European recognition for the Confederacy, Maryland's secession from the Union, and even placing enough political pressure on Lincoln to bring the war to a close. Should Lee achieve a victory in Maryland on par with the one he had achieved at Manassas in late August, the Civil War would likely have had a very different ending.
However, once in Maryland, Lee realized he had a pesky problem located at Harper's Ferry. 12,000 Union soldiers were garrisoned there. Lee had initially assumed these troops would vacate the town in favor of a safer location, but he had assumed wrong. Thus, the Confederate commander split his forces, sending Stonewall Jackson with 20,000 men to Harper's Ferry, and sending James Longstreet's wing of the army toward Hagerstown. While orders sending Longstreet to Hagerstown would be altered, leaving that wing near Boonsboro, the Confederate forces were now significantly divided. Moreover, it was only the division of Daniel Harvey Hill which was guarding South Mountain, the crucial geographical barrier between Lee and McClellan.
On the 14th of September, George McClellan caught up with Lee, and a fierce day long fight ensued. The Union 1st, 9th, and 6th Corps attacked at three crucial mountain passes, pushing back Confederate forces after an exhausting day long fight.
South Mountain is a battle which defies many existing stereotypes of both George McClellan and Robert E. Lee. McClellan, either the cowardly lion or the scarecrow of Union Civil War generals (depending on which historian you read), caught the supposedly always aware Lee unware. It was not until the night before the fight that Confederate forces began to realize how close the Union army was and in how great a number they were advancing. This battle is fascinating for many reaons, but perhaps the greatest of those reasons is that it is a complete anomoly in the typical narrative concerning these two famous generals. McClellan achieved a victory with crushing force and commendable speed, while Lee was defeated in a battle for which he was not ready and was not prepared.
Most importantly, however, South Mountain was what in part led to the Battle of Antietam. As I tell visitors to Antietam, up until September 14, Lee was in the driver's seat for the Maryland Campaign. He could dictate where the fighting occured, as his army had the intitiative. However, once George McClellan surprised and defeated Lee, it was imperitive that, rather than continuing with offensive operations, the Confederate forces either retreat from Maryland or make a hasty defensive stand. Effectively, South Mountain removed offensive operations from the range of possible options for Lee's forces. Certainly, it precluded the possibility of Lee's army reaching Pennsylvania. Now, the orders which Lee had issued splitting his forces seemed as though they could be the fatal mistake for the Confederate Army of Northern Virginia. Lee's army was still separated, and George McClellan was knocking on the door of victory. South Mountain fundamentally changed the nature of the Maryland Campaign.
On this evening 149 years ago, Robert E. Lee was being forced to reconsider his Maryland Campaign. If he didn't hear favorable news from Stonewal Jackson at Harper's Ferry soon, it might be time for retreat. What happened the next day influenced Lee's decision to move toward Antietam Creek...
Our Country's Fiery Ordeal
A blog about the American Civil War, written and maintained by historian Daniel J. Vermilya, author of The Battle of Kennesaw Mountain (History Press, 2014) and James Garfield and the Civil War (History Press, 2015)
Dedicated to my great-great-great grandfather, Private Ellwood Rodebaugh, Company D, 106th Pennsylvania Volunteer Infantry, killed at the Battle of Antietam, September 17, 1862.
"And may an Overuling Providence continue to cause good to come out of evil, justice to be done to all men where injustice has long prevailed, and finally, peace, quiet, and harmony to come out of this terrible confrontation and our country's fiery ordeal." -- Albert Champlin, 105th Ohio, Diary entry of June 19, 1864 (Western Reserve Historical Society)