With the advent of the rifled musket onto Civil War battlefields, the ability of a soldier on the defense to kill his attacking enemy rose dramatically. The former standard weapon had been the smoothbore musket. Such smoothbores had a maximum effective range of seventy-five meters. The new standard weapon, the rifled musket, had an effective range of 300 meters. Defenders, armed with this new weapon, could put attacking enemy soldiers under killing fire at a far greater range that ever before possible. Using the rifled muskets, defenders exacted punishing tolls before attackers closed within bayonet range for the close combat that furnished the cornerstone of contemporary tactical planning. As they made their tactical plans, commanders in the American Civil War seemed to ignore this deadly technological innovation, and Lee, Bragg, Burnside, Hood, Pope, and Jackson make a list of the worst offenders. They continued frontal assaults, assaults that brought their men directly under fire from the rifled musket. Bloody Civil War battles offer a litany of failed assaults: Manassas, Shiloh, Malvern Hill, Antietam, Fredericksburg, Gettysburg, and Cold Harbor. Where frontal assaults succeeded, the costs in soldiers’ lives were staggering. As casualties mounted astronomically, Civil War commanders must have realized that something was wrong on the battlefield. Yet, these commanders, with one important exception, rarely varied their battlefield tactics. Only one commander gave evidence of understanding the deadly message of the rifled musket, and the failure of Civil War tactics to silence or mute that message, Maj. Gen. William T. Sherman. This thesis examines that understanding and provides Sherman’s rationale for changing contemporary battlefield maneuvers. Sherman came to the conclusion that the tactics of the day could not defeat a defense armed with rifled muskets, so he changed the battlefield rules. In doing so, he defeated a determined and aggressive foe, inflicted more casualties on his enemy than his forces sustained, split the Deep South asunder, and hastened the end of the Civil War. / Master of Arts