Lee never confided his feelings about the battle to paper, but he had to have known that it was a disaster. The Confederacy could not afford battlefield casualties in the way that the Union could, and now he stood with the river to his back and McClellan’s army in front of him. Very likely, Lee knew the full extent of his peril. But he bravely acted as if the situation was under control.

When another day passed without a federal assault, Lee took his chance to escape. On the night of September 19 to 20, the Army of Northern Virginia began passing over the Potomac, departing Virginia. Remarkably, there was no attack, or even any sorties by the Federals, and the Army of Northern Virginia successfully exited Maryland. The Confederates had taken a bad beating, but they were still in the field.