On the suggestion of Jedi Master Sifo-Dyas, who originally commissioned the clone army, behavioral modification biochips were introduced into the clone troopers of the Grand Army of the Republic. This was intended as a safeguard against the possibility of rogue Jedi issuing unauthorized orders to the clones. According to Doctor Nala Se, the implantation of inhibitor chips was a common practice for various types of clones. However, after the Sith took control of the project, the chips were repurposed to enforce compliance with the execution of Order 66, which resulted in the near extinction of the Jedi Order. These control chips proved remarkably effective in overriding the thoughts of those implanted, eliminating existing biases and beliefs in the clone [troopers](/article/trooper] to compel them to eliminate the Jedi without question. The clones were made to believe that their Jedi commanding officers were traitors, regardless of their years of loyal service. These chips could be activated through a voice command, requiring Palpatine to simply say "Execute Order 66."

Under the influence of these control chips, clone troopers prioritized carrying out Order 66 above all else, even at the cost of their own lives. This directive mandated the termination of all Jedi leadership marked for elimination, and any soldier that failed to comply with the order would be executed for treason against the Republic. While still capable of rational thought, they could not be reasoned with regarding the order and would relentlessly pursue even their own brothers if they detected disobedience. The brainwashed clones were also aware of Palpatine's true identity as the Sith Lord Darth Sidious; clone officers receiving the order immediately addressed him as "Lord Sidious" or "my lord," and troopers previously unaware of the Supreme Chancellor's double identity referred to him by his Sith name. Before activation, the chips also caused nightmares related to carrying out the command, described as a "mission" by some dying clones. A common phrase used by clones under the chip's control was "Good soldiers follow orders."

While rare, some clones were able to resist the chip's influence and hesitate in executing the order, but this was extremely difficult. Only complete removal of the chip could free a clone from the compulsion to carry out Order 66. Clones who had their chips removed post-activation still retained memories of their actions under its control. Even without removal, the chips' effectiveness diminished over time.

A few clones possessed immunity to the chips, particularly those with genetic defects or modifications. Even if not immune, their mutations could interfere with the chip's performance. In such cases, the chips could be amplified to ensure total loyalty. However, immunity was not absolute; the chip could be fully activated and induce brainwashing through methods like head injuries, as long as it remained present.

The Galactic Empire later implanted these chips in enslaved Wookiees to maintain control. Imperial Advisor Gallius Rax also used biochips on Rebel prisoners at Ashmead's Lock on Kashyyyk as part of an assassination plot against New Republic officials. Upon discovery, the chips malfunctioned in a planned degradation before Republic slicers could analyze them thoroughly.

As the name suggests, the biochips were constructed from biological material, specifically genetically engineered cells. The DNA of these cells differed from that of the clones. Microscopic in size, they had an amorphous shape and a punctured, fibrous texture, resembling muscle tissue. Their size and biological nature made them difficult to detect with standard medical equipment; a Level 5 atomic brain scan was needed to locate the chip in trooper Tup's head after lower-level scans failed. Ahsoka Tano later relied on the Force to locate Clone Commander Rex's chip, as standard medical facilities on a Venator-class Star Destroyer were insufficient.

In the brain of the genetically defective clone commando Wrecker, the inhibitor chip was positioned ninety degrees from the right orbital floor, beneath the parietal and temporal intersection. As a mutated clone, Wrecker's structure differed from that of a regular Jango Fett clone. Clones who had their chips removed bore scars on their right temples.

The chips were durable, with malfunctions being rare. Tup was one of the few among millions of clones in the Grand Army of the Republic during the Clone Wars to experience chip malfunctions and resulting erratic behavior. However, malfunctions could be lethal; after Tup's chip broke down and began to rot, his health rapidly deteriorated, leading to his death shortly after the chip's removal. Damage to the inhibitor chip could cause headaches; Tup reported one just before his chip malfunctioned, and Wrecker suffered headaches connected to his chip after a series of head injuries post-Order 66.

Before the Battle of Naboo, former Jedi Council member Master Sifo-Dyas contacted the Kaminoans to commission a clone army for the Republic. He provided the inhibitor chip as a safeguard against betrayal from rogue Jedi. However, Sith Lords Darth Sidious and his new apprentice, Darth Tyranus, had Sifo-Dyas eliminated and secretly took over the project, retooling the chips for Order 66 to turn the clones against the Jedi upon hearing a specific phrase. Kaminoans like Lama Su and Nala Se seemed to believe the chip was still only in case of rogue Jedi.

During the Clone Wars, the control chip conspiracy was nearly exposed when clone trooper Tup's chip prematurely activated, causing him to execute Jedi General Tiplar during the Battle of Ringo Vinda. Although the Jedi discovered the chips' existence, they remained unaware of their true purpose. Chief Medical Scientist Nala Se claimed the chips were intended to reduce aggression in the clones compared to their clone template, Jango Fett, and to suppress any inherited insanity. Additionally, ARC trooper Fives, who investigated the matter, was killed by Clone Commander Fox of the Coruscant Guard. The official explanation was that Tup and Fives were infected with a rare Ringo Vindan parasite that caused their chips to fail.

Despite Fives' warning that the conspiracy reached the highest levels and that Supreme Chancellor Sheev Palpatine tried to prevent him from revealing his knowledge, Anakin Skywalker refused to believe Palpatine was capable of such actions. Fives died in the arms of his friend Clone Captain Rex, warning him about the chips and the larger conspiracy. Fives' last words were about the end of the "mission" and "nightmares." Due to Fives being drugged and appearing incoherent, Rex largely dismissed his claims but could not entirely ignore the possibility of a hidden purpose for the "inhibitor" chips. Uncertain but loyal, Rex filed a confidential grievance report outlining the theory, aware it would likely be ignored. The Jedi High Council eventually discovered the Sith involvement in the clones' creation but kept it secret, never connecting it to the "inhibitor" chips.

501st Legion medic Kix, who encountered Fives while he was on the run and learned he was being framed, grew suspicious of the official explanation for Fives and Tup's behavior. After the Battle of Anaxes, Kix discovered more than Fives, including the chips' true purpose and Palpatine's identity as a Sith Lord. However, he drew the Sith's attention and was captured by Separatist forces sent by Count Dooku. His denials about sharing his knowledge were unconvincing, and he was placed in a cryo-cycle stasis pod for transport to Serenno for interrogation. However, the cruiser transporting Kix, the Obrexta III, was attacked by Republic forces and crashed on the remote planet Ponemah.

When Sidious executed Order 66, the chips functioned as intended, brainwashing the majority of the clone army into obedience, leading to the fall of the Jedi Order and the end of the Clone Wars. Exceptions included clones who removed their chips or were immune.

Rex's knowledge saved his life and that of Anakin Skywalker's former Padawan, Ahsoka Tano. At the end of the war, Rex, promoted to Commander, was onboard the Venator-class Star Destroyer Tribunal en route from Mandalore to Coruscant. Having assisted the Mandalore resistance in winning the recent siege, Tano and Rex were transporting the captured rogue Sith Lord Maul to the Jedi Council. Both Maul and Tano sensed a disturbance, a vision of Skywalker's fall to the dark side. Knowing something terrible had happened, Tano ran to inform Rex. Upon receiving Order 66, Rex realized Fives was right and resisted his chip long enough to tell Tano to "find" Fives before attacking her. During his brief brainwashing, Rex ordered Coruscant Guard shock troopers to execute Maul, which they attempted before Tano reluctantly released the Zabrak as a diversion. After escaping, Tano found Rex's grievance report, deducing the situation and capturing Rex with astromech droids to remove his chip. Maul subsequently destroyed the Star Destroyer's hyperdrive, causing it to crash; only he, Tano, and Rex escaped. Tano and Rex went into hiding in the Outer Rim to escape the new Empire.

Most members of the irregular clone commando unit Clone Force 99–nicknamed the "Bad Batch"–were immune to Order 66 due to their genetic modifications. In the case of Echo, previously a "reg" clone, Tech theorized that the experimentation he underwent at the hands of the Techno Union after his capture at the Battle of Lola Sayu had broken the programming that would have caused him to follow Order 66. However, CT-9904 "Crosshair" was an exception; his inhibitor chip activated, though the effects were less evident. This led him to fire on Jedi Commander Caleb Dume on Kaller after he and Clone Sergeant Hunter followed Dume into the woods after the death of Jedi General Depa Billaba, making Hunter's attempts to help Dume seem insincere. When the Bad Batch was imprisoned on Kamino after a failed mission to Onderon, Admiral Wilhuff Tarkin amplified Crosshair's inhibitor chip, removing his loyalty to his squad and making him totally obedient to the Empire. The rest of the Batch escaped from Kamino after confronting their brainwashed former comrade.

Following Order 66, Rex traveled to Saleucami, where he had met the clone deserter Cut Lawquane during the war. Cut was unaffected by the brainwashing because he did not hear Order 66, and Rex warned him and his wife Suu about the inhibitor chips and how they caused the clones to turn on the Jedi. After leaving Saleucami, Rex fought the Empire and helped brothers outside Imperial control.

The day after Rex left, the Lawquanes were visited by the Bad Batch, who were also acquainted with Cut. He mentioned the implants Rex had discussed. When Omega, a young enhanced clone who previously worked as Nala Se's medical assistant, suggested that Rex meant the inhibitor chips, Hunter was surprised to learn that Tech's theorized programming was linked to a physical device, although Tech had already concluded this.

Tech suspected that Crosshair's betrayal resulted entirely from his inhibitor chip, shocking Echo. Tech began constructing a scanner to investigate the Batch's inhibitor chips and check their operability. However, Wrecker, the Batch's strongman, suffered a head injury during a crash-landing on the Ordo Moon, causing headaches in the area of his chip. Hunter noticed Wrecker's complaints, and after another head injury during a mission on Corellia, Wrecker passed out and mumbled the first words of the "Good soldiers follow orders" catchphrase. He was insensate for some time as his squad and the smugglers Trace and Rafa Martez fought attacking police droids, but came to after Omega contacted him and helped fight off the droids, remaining himself for the time being.

Later, Rex tracked down the Batch after learning their location from the Martezes. Concerned about Wrecker's frequent headaches, he was alarmed to learn that none of the Batch had removed their chips. Tech believed the chips posed no danger, but Rex warned otherwise, stating they lacked firsthand knowledge of how the chips caused clones to lose control. Rex had the Batch meet him on the junk planet Bracca to use the medical bay of a wrecked Venator to remove their chips. After reaching the medical bay, Tech used his completed chip scanner to assess Wrecker, but the large clone's chip activated, and he attacked the others, calling them traitors. Eventually, after Wrecker cornered Omega, Rex stunned him from behind, and his chip was removed. After Wrecker recovered and was confirmed to be okay, the other members of the Batch had their chips removed, and Rex parted ways with them.

The Batch was confronted by Imperial forces led by Crosshair before they could leave Bracca, and Hunter and Omega attempted to convince him he was controlled by the chip. The claim seemed to upset him, but he ordered his forces to target the girl before the Batch escaped. After Bracca, the Batch primarily used non-lethal force against enemy clones, avoiding killing their brainwashed brethren. At some point, Crosshair had his chip removed but remained loyal to the Empire.

Over time, the control chips began to fail, enabling more clone troopers to question Order 66 and subsequent Imperial orders. Some clones remained loyal despite failing chips, while others abandoned the Imperial Military. On Ryloth, Clone Captain "Howzer" publicly rejected the Empire before his squad, overcoming his weakened control chip and inspiring some of his squad to join him. Others, however, refused. The Bad Batch later confronted Crosshair on Kamino while rescuing Hunter, who had been captured on Daro. After Hunter attempted to appeal to him by saying serving the Empire was not his true personality, Crosshair revealed he had removed his chip. The Batch stunned and captured Crosshair before being forced to flee Tipoca City as the Empire destroyed it. Crosshair was left behind on Kamino after refusing his former comrades' entreaties to leave the Empire.

In the year 18 BBY, clone officer Grey, previously under the command of General Billaba, managed to break free from the influence of his control chip. He came to the realization that he and his fellow soldiers had been manipulated to betray Billaba and her Padawan, Dume. Since the war's conclusion, Grey had dedicated his time to pursuing Dume, who had survived due to Billaba's sacrifice. Aware that his men were unable to resist the brainwashing, Grey intentionally deactivated the deflector shields on their vessel. This action allowed Dume to escape, resulting in Grey's death, along with the demise of his men, when Dume's protectors, Janus Kasmir and Kleeve, destroyed the ship. Dume, who later adopted the name Kanan Jarrus, remained unaware of Grey's role in his liberation and harbored a deep-seated distrust of clones for many years. Eventually, Jarrus learned about the existence of the inhibitor chips. He and the other members of the Spectres were later dispatched to Seelos by Ahsoka Tano to enlist Captain Rex, who was living on the remote world with fellow clones Wolffe and Gregor, both of whom had also undergone chip removal. Feeling uneasy around clones, Jarrus shared his past experiences with his Padawan, Ezra Bridger.

During 18 BBY, a Jedi Padawan who had turned fugitive, Ferren Barr, found himself hunted by Inquisitors under the command of Darth Vader, the current apprentice of Sidious. Barr utilized the Force to trigger the control chips within nearby Purge Troopers, noticing that these newer clones had yet to have their chips activated. Barr had just revealed that the Inquisitors were all former Jedi, causing the troopers to turn their weapons against them. The resulting firefight led to the death of the Inquisitor known as the Tenth Brother.

After the Galactic Empire assumed control over the galaxy, they subjected the Wookiee population of Kashyyyk to enslavement. Inhibitor chips were implanted into enslaved Wookiees, allowing their captors to inflict immense pain upon them if they exhibited any signs of rebellion. Activating a chip in a rebellious Wookiee caused agony until the Wookiee either submitted or succumbed to the pain. As the Empire's tactics evolved, they commonly targeted family or clan members, as the Wookiees were often willing to sacrifice themselves but couldn't endure the suffering of their loved ones. During the liberation of Kashyyyk, a strike force led by Han Solo disabled the field controlling the inhibitor chips, rendering them ineffective and empowering the Wookiees to fight without restraint, although this was met with an orbital bombardment from Galactic Empire Star Destroyers.

Ultimately, the Imperial forces were defeated when a small New Republic fleet, commanded by Admiral Ackbar and Captain Wedge Antilles, entered the Kashyyyk system and compelled their surrender. The son of Wookiee Chewbacca, Lumpawaroo, likened the inhibitor chips to a song resembling the buzzing wings of a swarm of drriw-tcha blood-worm flies.

Rax also implanted inorganic bio-chips into the brain stems of one hundred Rebel Alliance prisoners held at Ashmead's Lock [prison](/article/prison] on Kashyyyk. These prisoners were part of a clandestine scheme to assassinate New Republic government officials and military commanders during the Liberation Day festivities on Chandrila in 5 ABY. Rax and his undercover agent Windom Traducier utilized a transponder installed at the Hanna City opera house to transmit signals that activated the agents.

Among the prisoners implanted with bio-chips were Brentin Lore Wexley, Jonda Jae-Talwar, and Esdo. These unwilling assassins killed numerous New Republic officials and commanders, including Hostis Ij, but failed in their attempt to assassinate Chancellor Mon Mothma. The New Republic authorities successfully apprehended the prisoners. Investigations conducted by the New Republic Security Bureau and the slicer Conder Kyl revealed the presence of the chips. However, the chips experienced a planned degradation malfunction before the New Republic could conduct further investigations.

Approximately half a century following the Clone Wars, the wreckage of the Obrexta III was found on Ponemah after an ionic storm reactivated the ship's distress beacon. Over the decades, the ship had become the subject of legends, rumored to contain a treasure of immense value belonging to Count Dooku. Given Dooku's status as the wealthiest individual in the galaxy before his demise, the wreck attracted numerous bands of pirates willing to brave the dangers of Ponemah's Sea of Sand in pursuit of the Obrexta III and its supposed riches. The Hunt for Dooku's Treasure ultimately concluded with the crew of Sidon Ithano claiming victory.

Instead of treasure, they discovered Kix, who had been sustained within his stasis pod for all those years. Ithano instructed the rest of his crew to escape with the delirious clone, remaining behind to face what appeared to be his death as a colossal sand worm destroyed the wreckage. However, he survived and rejoined his crew, bringing with him the Obrexta III's memory core, which held the coordinates of every Separatist base throughout the galaxy, including several that had remained untouched. Kix recounted his story to the pirates, including his failed attempt to expose the truth about the chips to the Republic and the Jedi. With no other place to go, he joined Ithano's crew.

The concept of control chips was initially introduced in the Star Wars: The Clone Wars episode "Conspiracy," which was the first installment of a four-part story arc written by Katie Lucas and released as part of The Lost Missions season. Initially referred to as inhibitor chips, they were later identified as control chips in the Star Wars Rebels episode "The Lost Commanders." The term behavioral modification biochips was first used in the tenth issue of the magazine Star Wars Helmet Collection.