Company (United States Army)
A company is a military unit of the United States Army which has been in use since the American Revolutionary War. It has historically been commanded by a Captain, assisted by a First Sergeant as the senior-most non-commissioned officer (NCO), and consisted of approximately one hundred soldiers. Soldiers were divided between three and five platoons of around thirty each and led by a lieutenant. However the exact size and composition of a company has varied depending on the time period and its role. Companies in the US Army may be categorized as maneuver companies , the combat arms (infantry, tanks, artillery, etc.) which directly engage the enemy in combat, and support companies which provide administrative and logistical support to the combat arms in carrying out their mission. Companies operate as part of a parent battalion, however they may also be organized as independent companies. Such units are typically specialized forces such as military police or medical personnel. In both cases though, companies require support from higher formations as they are not meant to conduct independent operations. In the US Army, company-sized units of cavalry and artillery are referred to as a troops and batteries , respectively. Civil War. During the American Civil War the company was considered the smallest military unit of the Union Army. The exact size and composition, however, depended not only on to which combat arm it belonged, but whether it was part of the Regular Army (USA) or raised by the individual states as United States Volunteers (USV). Infantry Company. Infantry companies which belonged to the Regular Army's ten original regiments (1st through 10th) were authorized a captain, a first lieutenant, a second lieutenant, four sergeants (one of whom was first sergeant), four corporals, two musicians, and forty-two privates  (some regiments were authorized seventy-two privates per company). After the war started, nine new infantry regiments (11th through 19th) were authorized companies with a slightly different structure, adding a fifth sergeant, four additional corporals, and up to eighty-two privates. Volunteer companies mirrored the "new" Regular companies but added a wagoner and could have between sixty-four to eighty-two privates. The wagoner was in charge of the company's wagon which carried its supplies, although during the war supply wagons were organized into trains placed under the control of regimental and higher commands. A company could be further  divided into smaller sub-units, although these were rarely used in actual battle (with the exception of skirmishing) given the linear tactics of the time. One company could split into two platoons, with each divided into two sections and each section into two squads. The smallest sub-unit were "comrades in battle" or the four men adjacent to each other in the line of battle. Conversely, two companies operating together were considered a division. Cavalry Company. Prior to the Civil War, the Regular Army's mounted soldiers were divided between cavalry, dragoons and mounted infantry. Dragoons were cavalry who primarily  fought dismounted while mounted riflemen fought similarly but were armed with rifles instead of carbines or muskets. Despite these differences the companies for all three were similarly organized: a captain, a first lieutenant, a second lieutenant, four sergeants, four corporals, two musicians, two farrier/blacksmiths, and a hundred privates (although just sixty-four for mounted riflemen). In July 1861, Congress authorized the addition of a new mounted regiment, the 3rd Cavalry, for the Regular Army and the raising of Volunteer cavalry regiments. Each company was similar to the "old" company with the addition of a first sergeant, a quartermaster sergeant , four additional corporals, a saddler, a wagoner, and up to seventy-two privates. Saddlers were responsible for keeping the horse-equipment of the company under repair; while not responsible for ordinary military duty they were to be instructed in it all the same in case of necessity. A year later, the organization of all cavalry forces were streamlined and companies were officially renamed troops. Each troop consisted of a captain, a first lieutenant, two second lieutenants (one of them a supernumerary), a first sergeant, a commissary sergeant, five sergeants, eight corporals, two teamsters, two farriers/blacksmiths, a saddler, a wagoner , and seventy-eight privates. A final organizational change was issued in April 1863, removing the supernumerary second lieutenant and the teamsters and adding two trumpeters to each troop. Artillery Company. The four artillery regiments of the Regular Army (1st, 2nd, 3rd and 4th) were all organized similarly with twelve companies, each company composed of a captain, two first lieutenants, two second lieutenants, four sergeants, four corporals, two musicians, two artificers, and forty-two privates (sixty-four if organized as field artillery). In May 1861, Congress authorized the creation of a 5th Artillery Regiment and the raising of Volunteer artillery forces  which were organized differently from the first four. Their companies (officially termed batteries now) were each authorized a captain, first lieutenant, second lieutenant, first sergeant, quartermaster sergeant, four sergeants, eight corporals, two musicians, two artificers, a wagoner, and between fifty-eight and one hundred twenty-two privates. The battery could be expanded with an additional first lieutenant, second lieutenant, two sergeants, four corporals, and four artificers. Each battery had four, six or eight cannons, with a sergeant designated as Chief of Piece for each cannon and corporals assigned as gunners; two cannons were together organized as a section and commanded  by a lieutenant. There was further differentiation between batteries depending on whether they consisted of heavy artillery, field artillery or horse artillery. Engineer Company. The United States Army Corps of Engineers had a single company of combat engineers when the civil war began. Engineer Company A had been originally created by an act of Congress at the start of the Mexican-American War. It was organized with ten sergeants (master-workmen), ten corporals (overseers), two musicians, sixty-four first-class privates (artificers) and sixty-four second-class privates (laborers). In August 1861 Congress authorized the formation of three more companies  to be organized the same as Engineer Company A, with all four organized into a single battalion (the US Engineer Battalion, later 1st Engineer Battalion). While trained engineers were required for complex tasks such as constructing pontoon bridges, most engineering work could be carried out by regular soldiers under supervision. For these purposes Union armies would detach soldiers from their normal duties to form company-sized units of pioneers. Their typical tasks during a campaign were to repair roads and clear obstacles for advancing forces, or to bury the dead after a battle.