How were continental army defeats under general greene a rallying point for the colonists?

Gen. Lee's reinforcements saved his forces, and the Union troops were pushed back to the bridge. But at the end of all the combat, with 23,000 casualties and 12 hours of fighting, Snyder says everyone was just about where they were when they started.

"The lines shifted [about] a hundred yards," he says.

It was basically a stalemate.

Late the next day, Lee slipped his army across the Potomac. The Union commander, Gen. George McClellan, failed to pursue Lee. He was soon fired by President Lincoln.

The partial victory at Antietam, however, gave Lincoln what he needed to issue the Emancipation Proclamation that would free the slaves in the Confederate states the following January.

After Antietam, the war would no longer be just about preserving the Union.

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