The type of warfare primarily used at the Battle of Antietam was open-field combat.

The battle fought on September 17, 1862, took place across a largely rural landscape, featuring rolling hills, fields, and key landmarks such as the Sunken Road and Antietam Creek. Troops engaged in direct confrontations, often launching frontal assaults against each other’s positions. This style of combat highlighted the brutal nature of the Civil War, as soldiers faced devastating fire from rifled muskets and artillery. The combination of open terrain and aggressive tactics contributed to the battle's high casualty rate and intensity.