Artillery troops were divided into two kinds, light and heavy, a convenient relationship to the mobility of the pieces they served. Columbiads, mortars, and the heavy guns, rifles, and howitzers, were served by the heavy artillery. These, in turn, were classified according to their use as siege, garrison and seacoast artillery. Heavy artillery units employed as siege artillery operated with the armies in the field serving the 30- and 20-pounder Parrott rifled guns, 12- and 24-pounder guns, 8- and 10-inch mortars, and the 24-pounder Coehorn mortar. They defended fixed positions in the field and were used to bombard enemy forts and entrenchments.
Garrison artillery was employed in the defense of forts and generally used the same kinds of ordnance as the siege artillery, the chief distinction being the carriages upon which the pieces were mounted.
Light, or field artillery, maneuvered with the troops in the field, and employed light and mobile pieces drawn by horses. The most popular field pieces used were the 12-pounder Napoleons, the 3-inch rifles, and the 12-pounder howitzers. The 6-pounder smoothbore was used extensively in the early part of the war, but it was replaced by rifled pieces.
Light artillery was divided into two categories, horse artillery which was attached to the cavalry with the cannoneers mounted on horseback, and the mounted artillery which usually maneuvered with the infantry, the cannoneers marching on foot beside their pieces or, when necessary, riding atop the ammunition chests on the limbers and caissons.