The Galactic Republic clone troopers were programmed and trained the same way in skills and had the same appearance, but a few were designed different from the masses. The ultimate in the clone trooper ranks were the Advanced Recon Commandos, or ARC troopers, elite infantry units, who were personally trained by Jango Fett in the early times. The ARC troopers were used for only the most dangerous missions that required independent thought. Though these troopers undergo growth acceleration like the standard clones, their docility and independence has not been at all altered. ARC troopers carry heavier weaponry or mission-specific gear such as reverse-polarity pulse grenades or PLEX-1 portable missile launchers. They have an advanced version of the clone trooper armor, too. The ARC trooper armor was a specialized variant of Phase I clone trooper armor. The armor was lighter and offered more protection than standard clone trooper armor and could be fitted with specialized attachments, such as a jetpack, rocket dart launchers, miniature flamethrowers, and a rangefinder, binoculars, or even a lamp. The ARC Trooper, Fordo, also had a taser that could be shot from his gauntlet which he used against Durge at the Battle of Muunilinst in the Clone Wars cartoon. ARC trooper armor was usually worn with a blast dampening kama and rank signifying pauldron. Also, they liked to have some unique accessories, like a skirt, beltpack, unique paintings on the armor. By the Battle of Coruscant, it was show that the armor presumably had a Successor, as Fordo was wearing Phase II clone trooper armor. Advanced Recon Commandos, also known as Advanced Recon Clone troopers or simply ARC troopers, were elite variants of clone troopers in the Grand Army of the Republic during the Clone Wars. However, they were less numerous than other clones they were among the most skilled soldiers in the galaxy; and soon became the well-known, and respected heros of the Clone Wars.

The background story of the ARC troopers

 During the early stages of the clone army's development, Jango Fett and his Mandalorian military advisors advocated the creation of a new clone service which would be capable to handle covert missions too delicate for the standard clones. To achieve the desired results, the Kaminoans did not apply the standard behavior correction and enhanced the prime clone's genetic sample to increase physical prowess. The first attempt often end in failure in the scientific experiments. So the Kaminoan genetic alterations were unsuccessful first, resulting in the Null-class ARC troopers. Learning from the lesson, the Kaminoans succeeded in their second attempt, generating the first 100 ARC troopers, designated the Alpha-class. After completing standard flash training and accelerated growth, these clones were placed under the direct tutelage of Jango Fett. Under Fett's strict discipline they learned to use their fierce independence, innate creativity, and physical superiority in combination with their training in advanced weapons and vehicles to become virtual one-man armies. After completing their training, the ARC troopers were locked in stasis on Kamino until they were required.

ARC troopers against General Grievous