Lincoln, Abraham (1809-1865) to John J. Key

The United States achieved independence in part because foreign countries such as France and Spain entered the war against Britain on the American side. The Confederacy, too, hoped for foreign aid. In a bold bid to win European support, the Confederacy sought to win a major victory on northern soil.
In September 1862, Lee launched a daring offensive into Maryland. No one could be sure exactly what Lee planned to do. But in an incredible stroke of luck, a copy of Lee's battle plan (which had been wrapped around three cigars) fell into the hands of Union General George B. McClellan. After only a brief delay, on September 17, 1862, McClellan forces attacked Lee at Antietam Creek in Maryland.
The Battle of Antietam (which is sometimes referred to as the Battle of Sharpsburg) produced the bloodiest single day of the Civil War. Lee suffered 11,000 casualties; McClellan, 13,000. Lee was forced to retreat, allowing the North to declare the battle a Union victory. But Union forces failed to follow up on their surprise success and decisively defeat Lee's army.
Lincoln deeply mistrusted McClellan, an obsessively cautious general and a Democrat who bitterly opposed the Emancipation Proclamation and who called Lincoln the "Gorilla." In the following exchange of letters, Lincoln expresses his anger over the statement of one officer, Major John J. Key, whose brother was a key McClellan adviser, that it was not the objective of the war to crush the Confederate army. Instead, Key implied, the goal was simply to drag the war out until both sides gave up and the Union could be restored with slavery intact. Key was the only officer to be dismissed from service for uttering disloyal sentiments.