What is the impact of Antietam? The Battle of Antietam makes every list of the Civil War’s greatest battles, in terms of both scale and effects. All know that it was a frighteningly bloody and vicious affair that saw about 3,560 killed and 17,300 wounded within one day (and many of the wounded would have eventually died due to their wounds, raising the death toll). Less clear is the effects of the battle itself, which has been debated by various historians.