501st Legion The 501st Legion , also referred to as the 501st Battalion and later known as " Vader ' s Fist , " was an elite military division of the Grand Army of the Republic . Consisting of highly - trained clone trooper s engineered by Kaminoan cloners , the 501st served under the command of the Jedi Knight Anakin Skywalker throughout the Clone Wars . It was deployed to numerous contested planet s across the galaxy during the conflict between the Galactic Republic and the Confederacy of Independent Systems , including Christophsis , Geonosis and Umbara . Command of the legion was temporarily reassigned to Jedi General Pong Krell , whom the 501st mutinied against after learning of his fall to the dark side of the Force . As the war progressed , CT - 5555 — an Advanced Recon Commando who served in the 501st — discovered a plot to destroy the Jedi Order , but was killed by CC - 1010 of the Coruscant Guard before he could prove it . Although the 501st faithfully served both the Republic and the Jedi , the clone trooper s were compelled by their programming to execute Order 66 , a secret protocol designed to force the clones into killing their Jedi officer s . As such , the 501st marched on the Jedi Temple of Coruscant and , with the aid of Skywalker — now the appointed Sith Lord Darth Vader — proceeded to purge its inhabitants , including Padawan s and younglings . Afterward , the 501st gained the nickname " Vader ' s Fist " and continued to serve as his personal stormtrooper legion under the new regime of the Galactic Empire . Approximately two decades after the proclamation of the New Order , the 501st fought the Rebel Alliance at the Battle of Hoth in 3 ABY during the Galactic Civil War . By then , the Imperial Military had supplanted its clone units with birth - born human recruits . History . Clone Wars . The 501st Legion was composed of clone trooper s that had been engineered as part of an army to serve the Galactic Republic . It was divided into multiple sub - units such as Torrent Company , which served in the first battle of the Clone Wars — the galaxy - wide civil war between the Republic and Separatist Alliance — under the leadership of Clone Captain CT - 7567 ( " Rex " ) . Following the Republic victory on Geonosis , the 501st was deployed to the front lines as part of the newly - formed Grand Army of the Republic . Early missions . The Jedi Order , guardians of peace and justice , accepted a commission as leaders of the Republic military . As a result , the 501st was placed under the command of Anakin Skywalker — recently promoted Jedi Knight and General of the Grand Army — with Captain Rex serving as his first officer . During the Battle of Christophsis , Ahsoka Tano became apprentice to Skywalker , and therefore served as a Jedi commander in the 501st . After securing victory alongside the 212th Attack Battalion on Christophsis , the 501st was redirected to the planet Teth with orders to rescue Rotta , son of the Hutt crime lord Jabba Desilijic Tiure . They sustained heavy losses against the Separatist Droid Army , but ultimately prevailed in the Battle of Teth with the support of Jedi Master Obi - Wan Kenobi and the 212th . Skywalker ' s legion continued to serve the Republic over the course of the war , completing a variety of assignments and gaining new trooper s — such as CT - 1409 ( " Echo " ) and CT - 5555 ( " Fives " ) — deemed worthy of serving in the ranks of the elite 501st . As Skywalker often worked alongside his mentor , Kenobi , the 501st also served with the 212th on several missions , including the voyage of Duchess Satine Kryze from Mandalore to Coruscant . The Death Watch , a terrorist organization opposed to Kryze ' s government , failed to assassin ate the duchess before she could reach the galactic capital due to the combined efforts of the 501st and 212th . Later , a detachment of the 501st was sent to Naboo along with a squad of clone ordnance specialist s where they ultimately prevented Doctor Nuvo Vindi ' s plan to attack the population through biological warfare . Following the theft of a holocron from the Jedi Temple on Coruscant , the 501st ' s Carnivore Battalion was sent on a mission to Devaron in order to retrieve the artifact from Cad Bane . In the ensuing battle between the Republic and Separatist forces , the battalion manned the All Terrain Tactical Enforcer , designated 773 , alongside two other brigade s . The bounty hunter was presumed to have died in the battle , but in fact survived by disguising himself with the clone armor of the 501st trooper Denal . Battle of Kamino . When the Separatists plotted to deal the Republic a crippling blow by destroying the cloning facilities of Kamino , the 501st and 212th rushed to the defense of their homeworld . The Battle of Kamino was a hard - fought victory for the Republic , due in part to the actions of the 501st . In particular , the troopers Echo and Fives were recognized for their service by Captain Rex , as well as CC - 2224 ( " Cody " ) of the 212th , and were both promoted to the elite status of ARC trooper in the aftermath of the battle . Afterward , Rex and the new ARC troopers of the 501st were sent with Skywalker and Kenobi to infiltrate the Citadel . Though succeeded in reacquiring the information pertaining to the Nexus Route from General Even Piell and his captain , Wilhuff Tarkin , the group lost Echo , who survived but was presumed dead , in addition to several other casualties . Battle of Umbara . The 501st was along the battalions that the Republic deployed to reconquer Umbara from the Separatist Alliance . During the campaign , Skywalker was recalled to Coruscant by the Jedi High Council at the request of Supreme Chancellor Sheev Palpatine , leaving the 501st under the command of Jedi General Pong Krell . Although he was a recognized war hero with a distinguished record of service , Krell became a Separatist spy after turning to the dark side of the Force . He deliberately sabotaged his own strategies to undermine the clones , whom he regarded with contempt and disgust . Krell ' s betrayal was exposed after deceiving the 501st and 212th into fighting each other , causing clones on both sides to kill each other by mistake . Both battalions mutinied against his command , causing the fallen Jedi to slaughter many clones before he fell into captivity . In response to his actions , Krell was summarily executed by his most loyal soldier , " Dogma , " who was subsequently taken into Republic custody for killing an officer . Conspiracy of Order 66 . During the Battle of Ringo Vinda , the 501st was forced to retreat from the Separatists due to an unexpected development : CT - 5385 ( " Tup " ) killed Jedi General Tiplar . Suffering from a malfunction in his inhibitor chip , the trooper became hostile towards the Jedi , which in turn led to a premature execution of Order 66 — a clone protocol designed to turn the clone army against their Jedi officers in the event of a Jedi rebellion . This turn of events led to an investigation on Kamino , but later moved to Coruscant at Chancellor Palpatine ' s request . By then , ARC trooper Fives had partially uncovered the nature of the inhibitor chips and , believing they were a threat to the security of the Grand Army , requested their immediate removal from the brain s of every clone trooper . However , the Chancellor revealed his knowledge of the chips and their true purpose to Fives , causing the clone to become a fugitive after attempting to assassinate Palpatine . The rogue clone made an effort to expose Palpatine ' s conspiracy , but was killed by CC - 1010 ( " Fox " ) of the Coruscant Guard before he could prove his claims . In 19 BBY , approximately three standard year s since the start of the Clone Wars , the conspiracy that Fives discovered came to fruition with the mass execution of Order 66 , leading the Grand Army to betray their Jedi leaders . Palpatine , who had orchestrated the Clone Wars as Darth Sidious , Dark Lord of the Sith , utilized the clone army as the instrument of both the fall of the Jedi Order and the Sith ' s rise to absolute power . Aiding the Dark Lord in the initial phase of the Jedi Purge was Anakin Skywalker , now anointed in the dark side as the Sith Lord Darth Vader . Sidious ' new apprentice was tasked with leading the 501st Legion in a direct attack on the Jedi Temple , resulting in the deaths of its inhabitants while thousands of Jedi were killed by their troops across the galaxy . By then , the 501st served under Clone Commander " Appo , " who was originally a clone sergeant during the invasion of Umbara , in addition to Vader . The commander was severely injured by Padawan Zett Jukassa before the latter was killed by a squad of 501st troopers , an incident witnessed by Senator Bail Organa of Alderaan . Following their siege of the Jedi Temple , the 501st patrolled the grounds around the site . Galactic Civil War . In the aftermath of Order 66 , Sidious consolidated his power as Emperor of the First Galactic Empire . The new regime retained the Grand Army as the first generation of Imperial stormtrooper s with the 501st Legion remaining under Vader ' s personal command . Over the course of the Empire ' s reign , the 501st acquired the nickname " Vader ' s Fist " due to their association with the Emperor ' s chief enforcer . By the time of the Galactic Civil War , the legion was deployed against the forces of the Rebel Alliance , ultimately serving in the Battle of Hoth three years after the Battle of Yavin . Although the 501st went on to serve the Republic ' s successor , Captain Rex chose to oppose the Empire having never executed Order 66 due to the removal of his chip prior to the event . After spending years in retirement , the aging clone veteran contributed his skills and experience to the fledgling rebellion that culminated in the formation of an alliance to restore the Republic . Equipment . The 501st Legion utilized the Phase I clone trooper armor during the early period of the Clone Wars , from the first battle on Geonosis until the introduction of the Phase II model by the time of the Battle of Mon Cala . On certain occasions Rex and other members of the 501st made use of jetpack s for aerial transportation and greater mobility . In general , the 501st maintained the appearance of the standard clone trooper as designed on Kamino . However , Captain Rex became part of a growing trend of clone officers who customized their uniforms with unique color - based designs and supplementary pieces of armor . By the time of the Battle of Christophsis , Rex wore his armor with blue markings , a command pauldron , and a kama . Over time more troopers of the 501st came to customize their own kit , also using blue as a complementary color to the standard white . As the war continued , Phase II clone trooper armor became widespread within the ranks of the Grand Army , supplanting the Phase I model . When the 501st upgraded their armor , they adopted a common color scheme and markings that identified their unit affiliation . Nevertheless , some clones — such as Rex , the ARC troopers , and even common soldiers — retained their own unique designs that differed from the rest of the 501st . Behind the scenes . " 501st Legion " is also the name of a fan costuming organization formed in 1997 by Albin Johnson and Tom Crews . The group originally intended to re - create accurate stormtrooper costumes , but has expanded to include Sith Lords , bounty hunters and other villains from the film series , encompassing EU source material as well as canonical ones . The group goes under the nickname , " Vader ' s Fist " , and was the inspiration for George Lucas to add the organization into official Star Wars canon . The group actively does charity and volunteer work for a number of organizations , and currently consists of over 10 , 000 members worldwide .