Lee was calm and confident.

The odds against him--and he knew what they were--apparently mattered nothing.
He knew the strength and spirit of his army and to what a pitch it was keyed by victory.

Moreover, he knew McClellan, whom he had met at the Seven Days, and he believed, in truth he felt positive that McClellan would delay long enough for the remainder of Jackson's troops to come up.

Upon this belief he staked the future of the Confederacy in the battle to be fought there between the Potomac and the Antietam.

His troops were worn by battles and tremendous marches.