The Rail-class Advanced Recon Commando represented a generation of ARC soldiers, emerging after the era of the Galactic Republic. These troopers were secretly cultivated by Kaminoan scientists as part of a clandestine scheme to liberate Kamino from the control of the Galactic Empire. In contrast to the clone troopers who served during the Clone Wars before their transformation into Imperial stormtroopers, the Rail-class ARC troopers were specifically conditioned to maintain unwavering loyalty to their Kaminoan creators, rather than the Emperor Palpatine. Conceived as an elite complement to Kamino's force of Anti-Imperial clone troopers, these ARCs were stationed within the Tipoca City Cloning Facility, tasked with safeguarding the Kaminoans' invaluable developing batches of young clones intended for combat against the Empire.
Upon discovering Kamino's insurrectionist intentions, the Sith Lord Darth Vader dispatched a specialized detachment from the 501st Legion, led by the bounty hunter Boba Fett, to Kamino. Their mission was to completely eradicate the entire rebel clone army. Consequently, the Rail-class ARC troopers fought their inaugural and ultimate battle alongside the Anti-troopers during the Kamino uprising in 12 BBY.
Following the ascension of the Sith Lord Darth Sidious to the position of Emperor of the galaxy, he swiftly consolidated his grip on the Galactic Empire with ruthless efficiency. The Imperial stormtroopers, clones derived from the deceased bounty hunter Jango Fett, who had previously served as the Galactic Republic's clone troopers, paved the way for Imperial dominion. It was at this juncture that the Kaminoans found their own homeworld subjected to Imperial occupation by the very beings they had created.
Having erred in imbuing the original Fett clones with unwavering allegiance to the Republic, and consequently to the Empire, the Kaminoans resolved to correct their mistake by secretly cultivating a new clone army entirely devoted to their Kaminoan creators. While the majority of this army consisted of Anti-troopers, an elite contingent of soldiers was established to augment the standard forces. Thus, the Kaminoans engineered a novel generation of Advanced Recon Commandos—the Rail-class ARC troopers. Under the Kaminoans' supervision, the Rail-class ARCs, along with the rest of the rebel clones, were nurtured and trained for nearly a decade.
The Rail-class ARC troopers were outfitted with ARC-variant Phase I armor, incorporating command pauldrons and kamas. Their primary armament was the chainguns.
Roughly two decades after the Kaminoans initially produced the clone army for the Republic, the Sith Lord Darth Vader dispatched the 501st Legion with orders to eliminate the rebel clones and restore Kamino to Imperial control. The 501st's commanding officer for this mission was the bounty hunter Boba Fett, who himself was a clone of Jango Fett. While the Anti-troopers defended the outer perimeters of Tipoca City, the Rail-class ARC troopers remained inside the cloning facility, safeguarding the developing batches of rebel clones.
Despite their accelerated growth and training, the Anti-troopers proved to be no match for Fett and the battle-hardened stormtroopers of the 501st Legion, many of whom had gained experience during the Clone Wars. After breaching the facility, Fett and his stormtroopers were suddenly confronted by the Rail-class ARC troopers, some of whom attempted to extend the battle outside to prevent the Imperials from entering Tipoca City. However, their efforts were unsuccessful, and the life support systems were destroyed, resulting in the termination of the unborn Anti-troopers before they could participate in the conflict. With the rebel Kaminoans' capabilities to defend the city or cultivate another clone army severely compromised, they chose to flee Kamino before the battle was completely lost.
In the meantime, the remaining Rail-class ARC troopers joined forces with the surviving Anti-troopers in a desperate struggle against their relentless Imperial clone counterparts. Despite their valiant efforts, Fett and the 501st stormtroopers managed to force the rebel clones onto the platforms, where they were exterminated to the last clone. With the demise of the Kaminoan insurgents who had cultivated the rebel clone army, the Rail-class ARC troopers perished alongside the Anti-troopers, and the "clone rebellion" not only ended in failure but would remain a secret, as all information pertaining to the Kamino Uprising was classified.