Robert E. Lee's invasion of the north was stopped by George McClellan's finding of the Lost Order, culminating in the bloodiest day in American history.
Below are the links to each section of the essay.
1. The Lost Order – McClellan takes command of Pope's troops in the aftermath of the Second Battle of Manassas through to the discovery of the Lost Order (August 29 – September 13, 1862).
2. South Mountain – The Battle of South Mountain through the eve of the Battle of Antietam (September 14 – September 16, 1862).
3. The Bloodiest Day – The Battle of Antietam (September 17, 1862).
4. McClellan's Bodyguard – The Battle of Shepherdstown, and the aftermath of Lee's Maryland campaign (September 18 – November 10, 1862).
A. Order of Battle – The organization of the opposing armies during the campaign.
B. References – A list of references used to write the essay.