Special Order 191

Special Order 191 (the "Lost Dispatch," and the "Lost Order") was a general movement order issued by Confederate Army General Robert E. Lee in the Maryland Campaign of the American Civil War. A lost copy of this order was recovered in Frederick County, Maryland, by Union Army troops, and the subsequent military intelligence gained by the Union played an important role in the Battle of South Mountain and Battle of Antietam.

History
The order was drafted on or about September 9, 1862, during the Maryland Campaign. It gave details of the movements of the Army of Northern Virginia during the early days of its invasion of Maryland. Lee divided his army into pieces, which he planned to regroup later: according to the precise text Maj. Gen. Stonewall Jackson was to move his command to Martinsburg while McLaws's command and Walker's command "endeavored to capture Harpers Ferry." Maj. Gen. James Longstreet was to move his command northward to Boonsborough. D.H. Hill's division was to act as rear guard on the march from Frederick.

Lee delineated the routes and roads to be taken and the timing for the investment of Harpers Ferry. Adjutant Robert H. Chilton penned copies of the letter and endorsed them in Lee's name. Staff officers distributed the copies to various Confederate generals. Jackson in turn copied the document for one of his subordinates, Maj. Gen. D. H. Hill, who was to exercise independent command as the rear guard. Hill said the only copy he received was the one from Jackson.

About noon on September 13, Corporal Barton W. Mitchell of the 27th Indiana Volunteers, part of the Union XII Corps, discovered an envelope with three cigars wrapped in a piece of paper lying in the grass at a campground that Hill had just vacated. Mitchell realized the significance of the document and turned it in to Sergeant John M. Bloss. They went to Captain Peter Kopp, who sent it to regimental commander Colonel Silas Colgrove, who carried it to the corps headquarters. There, an aide to Brig. Gen. Alpheus S. Williams recognized the signature of R. H. Chilton, the assistant adjutant general who had signed the order. Williams forwarded the dispatch to Maj. Gen. George B. McClellan, the commander of the Army of the Potomac. McClellan was overcome with glee at learning planned Confederate troop movements and reportedly exclaimed, "Now I know what to do!" He confided to a subordinate, "Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home."

McClellan stopped Lee's invasion at the subsequent Battle of Antietam, but many military historians believe he failed to fully exploit the strategic advantage of the intelligence because he was concerned about a possible trap (posited by Maj. Gen. Henry W. Halleck) or gross overestimation of the strength of Lee's army.

The hill on the Best farm where the lost order was discovered is located outside of Frederick, Maryland, and was a key Confederate artillery position in the 1864 Battle of Monocacy. A historical marker on the Monocacy National Battlefield commemorates the finding of Special Order 191 during the Maryland Campaign.

Corporal Mitchell, who found the orders, was subsequently wounded in the leg at Antietam and was discharged in 1864 due to the resulting chronic infection. He died in 1868 at the age of 52. His wife received a pension in 1890.

In popular culture
In Harry Turtledove's Southern Victory Series alternate history novels, the point of divergence with recorded history is that the order is not discovered by Union troops, but is instead recovered by a trailing Confederate soldier. Without it, McClellan is unable to find Lee's army and the Battle of Antietam is not fought. Lee reaches Philadelphia and forces McClellan to fight in an unfavorable position. The Confederate States of America is able to crush the Army of the Potomac at Camp Hill, securing with the win support from Britain and France, so the Emancipation Proclamation never occurs, and the Union is forced to give the Confederate states independence. The USA and CSA with their allies (the USA eventually allies with the World War I-era Central Powers) go on to fight three more bloody wars, first being the fictional Second Mexican War and the last two wars being alternate versions of World War I and World War II.

Union troops not discovering the order is also the point of divergence for the alternate reality superhero comic book series Captain Confederacy.

In the game Chrononauts, this event is on the timeline.

Bernard Cornwell's novel The Bloody Ground, part of the Starbuck Chronicles, fictionalises the events and lead-up of Antietam, in which the order is central to the drama in the lead-up to the battle and an explanation is offered for how it ended up discarded in the field.