Why Was Antietam So Bloody?

Today is the 150th anniversary of the Battle of Antietam, the bloodiest battle in American history. About 23,000 men died, were wounded, or went missing over the course of the single-day battle. Why was Antietam so deadly?

Advanced technology, unwise tactics, and terrible decision-making. The combination of new rifles that could be shot with great accuracy from far away and old-fashioned battle lines led to unprecedented deaths in the Battle of Antietam (and in the Civil War in general). As in other Civil War battles, both sides in Antietam arranged their infantry shoulder-to-shoulder in two long parallel lines before marching into battle. This type of linear formation made sense in earlier years, when military weaponry consisted mostly of smoothbore muskets (which were accurate only at short range) and bayonets (which, likewise, could only be used at close range). But by the beginning of the Civil War, rifling—the use of helical grooves in the barrel of a weapon, which stabilize a bullet, leading to greater shooting accuracy—was widespread.