General Lee must have been a betting man. If he hadn’t been, he’d have been thirty miles south instead of in the rolling hills around Sharpsburg, given the fact that his army was outnumbered by McClellan some four to one. But, he’d bet that McClellan’s slow style coupled with the Halleck’s cautious nature would mean they’d move their Union men in about as fast as if all they had to do was watch corn grow. Halleck was in fact the Commander of all the Union armies but still Lee was right. McClellan’s army approached Sharpsburg from Washington so cautiously that it took over two and a half days to arrive.
Furthermore, with the work of Stonewall Jackson and JEB Stuart, Robert E. Lee learned that George McClellan had somehow intercepted his plans for Maryland and also that Harper’s Ferry had been captured by the Confederates. That gave Lee the upper hand in offensive strategy, and he wasn’t the kind to turn around and retreat. Not General Lee. And definitely not in his first major attack of the North.
Near Antietam Creek Lee’s men formed a line of incoming divisions who had marched hard from Harper’s Ferry and who would face the incoming enemy, the Union troops under McClellan. If his plan didn’t work, Lee’s men could be forced back to the Potomac River. But he was willing to accept the risk. It was simple. When it came to the Union command, General Lee was willing to accept the risk.