Special Infantry Division

The Special Infantry Division was an elite formation of standard clone troopers (who were often known as clone stormtroopers) in the Grand Army of the Republic during the Clone Wars. Though they were considered special forces, they were placed under the Army command structure and were distinct from the Special Operations Brigade (which comprised clone commandos and shadow troopers) and the Advanced Reconnaissance Force (which comprised ARF and ARC troopers). The tactics and organization of the Special Infantry Division later culminated into the Imperial Stormtrooper Corps, whose infantry operated in a similar fashion. The Imperial Stormtrooper Corps was sometimes mistakenly referred to as the "Imperial Special Infantry Division" (though the term "division" was incorrect, as the ISC fielded tens of millions of personnel). All clone troopers that survived the Clone Wars were automatically assigned to the newly established ISC whether or not they served as stormtroopers during the war, and thus all former clone troopers became stormtroopers.

Clone stormtroopers first appeared during the First Battle of Geonosis, during which at least 15,000 were deployed to supplement standard units. Over time, the number of clone stormtroopers increased to encompass 20% of the Grand Army of the Republic's total infantry (3% of all active military personnel deployed by the GAR, Judicial Forces, Sector Forces, and pro-Republic local forces combined), and clone stormtrooper detachments were found in nearly every legion. Some clone stormtroopers were even found among the Republic Judicial Forces, which were not comprised of any other clone personnel. Regular clone troopers were able to become stormtroopers by simply completing a course during Reassessment (a period in which a stationed clone trooper is withdrawn to Kamino to be reevaluated by drill sergeants and possibly reassigned to another formation or role; most clone troopers are reevaluated every three months, while others [particularly those in more active warzones] are reevaluated at intervals of five to seven months). This course was considered easy by most, however required a healthy memory as stormtroopers were expected to master every combat role, whereas regular clone troopers only specialized in one or two at a time. The slang term "stormpilot" referred to a clone pilot within the Republic Starfighter Corps who had multiple aerial specialties (starfighter piloting, bomber piloting, gunship piloting, etc), though this was only a colloquialism and clone stormtrooper units did not typically field their own aerial detachments, instead relying on the formation they were assigned to for air support and transportation.

Organization
Unlike standard GAR formations, the Special Infantry Division was not divided among regiments, battalions, etc, but instead was divided into "Special Companies" comprising anywhere from 100 to 300 troopers. Some Special Companies were further divided into platoons and squads. Each Special Company was assigned to a different formation (for example, "Torrent" Company was assigned to the 501st Legion).

The Special Infantry Division was classified as a "stormtrooper formation", which meant that specialist units operated between multiple worlds and were not fixed to a single deployment like most standard GAR formations. This often meant that specialists were only present on any one world for the duration of their operation before being redeployed to another star system. Some formations such as the 501st Legion, 187th Legion, some battalions within the 41st Legion, the 212th Attack Battalion, 396th Attack Battalion, and 5th Assault Battalion had multiple Special Companies attached to them. This sense of constant mobility, hence the name "stormtrooper", was later carried over into the Imperial Stormtrooper Corps' infantry units (though the ISC did also have stationed units, often for the purpose of law enforcement).

Equipment and training
Clone stormtroopers wore standard GAR armor and were typically equipped with standard issue weapons (DC-15S, DC-15A blasters). Some stormtroopers also specialized in the use of the DC-15LE repeating blaster, Z-6 rotary cannon, and DC-15x sniper. A clone stormtrooper was indistinguishable from other regular clone troopers, though were allowed to customize their armor with paint jobs and other markings (for example, stormtroopers of the 501st had blue markings, 212th had orange, 187th had purple, 41st had green or grey, 396th had light blue, etc) whereas standard clone troopers were restricted to plain white-colored armor. Other specialized infantry types such as ARC troopers and clone commandos were also permitted to add markings to their armor.

Clone stormtroopers often operated to the same capacity of standard clone troopers, however were often had multiple specializations. For example, while a standard clone trooper may take the role of a rifleman, engineer/technician, medic, explosives expert, gunner, or scout in their unit, stormtroopers were trained in all of these fields (however not to the same degree as ARC troopers or clone commandos). Most clone stormtroopers were regulars that were reassigned to a Special Company during Reassessment. Later Imperial stormtroopers also studied multiple combat roles while training, though some units only required their infantrymen to specialize in one.