Rifle butt

The rifle butt is the standard melee attack in both The History Channel: Civil War – A Nation Divided and History Civil War: Secret Missions. By pressing the melee strike, the player smashes the shoulder stock of his firearm into an opponent, and usually takes one to two hits to kill. It is the weakest and with the least range of all melee weapons.

Unlike the bowie knife and cavalry saber, the rifle butt can be used in conjunction with a firearm. It and the bayonet are the only melee weapons/attack that is already attached to a firearm and does not need a weapon slot to be used.

For pistols, a similar attack known as the pistol whip is available in which the player smashes the wooden handle of his pistol into an enemy.

Appears in all missions.

Real life
Since back in the day, soldiers were not given any standard melee weapons besides a bayonet, it was very common in the Civil War for soldiers to use their weapons as clubs. During the Battle of Gettysburg, a Union soldier once struck a Confederate rebel with the butt of his rifle so hard, that the latter's skull split into two.