People who participated in this battle would be Robert E. Lee and both armies from both sides.
WHERE
During this battle, 20,000 people/soldiers had died. Nevertheless, this battle was awarded the most bloodiest one-day battle due to the casualties left on the ground.
WHY
The Battle of Antietam happened on September 17, 1862.
WINNER
This event had happened in Antietam Creek near the location, Sharpsburg, Maryland.
This event had happened because of the secreted plans from Lee were uncovered by the north, so then, the north had started engaging in the violence.