ES-03 was a human male individual within the Galactic Empire, identified by this designation. He was brought into the Empire's service in its early days by Vice Admiral Edmon Rampart. Rampart considered ES-03 and his fellow squad members to be among the most skilled soldiers throughout the galaxy. Consequently, he was integrated into the Elite Squad, which operated under the command of Clone Commander CT-9904. ES-03, alongside the other members of his unit, took part in the mission to Onderon, the Mission on Bracca, several engagements during the Ryloth Insurgency, but ultimately met his demise when CT-9904's deflected blaster fire resulted in the death of ES-03 and other Elite squad troopers.
Following the dissolution of the Galactic Republic and its replacement by the Galactic Empire in 19 BBY, the Imperial Military initiated a restructuring of its forces. As part of Project War-Mantle, Vice Admiral Edmon Rampart initiated the recruitment of humans to potentially take the place of the clone troopers who previously served the Galactic Republic. ES-03 was among the first to be selected and was regarded as one of the most exceptional soldiers in the galaxy. He was assigned to CT-9904's Elite Squad alongside fellow recruits ES-01, ES-02, and ES-04, operating under the direction of CT-9904. Subsequently, he was transported to the Tipoca City Military Complex, where he underwent examination by a Kaminoan medical droid.
Governor Wilhuff Tarkin issued orders for ES-03 and the Elite Squad to proceed to Onderon with the objective of eliminating a settlement of Saw Gerrera's Partisans. They arrived aboard a Nu-class attack/transport shuttle and navigated through the jungle terrain until they reached Saw Gerrera's camp. CT-9904, known as "Crosshair," neutralized several insurgents before directing ES-03 to advance through the jungle. While the majority of the insurgents were killed, some, along with all the refugees, managed to board their starship. Although the ship successfully took off, the pilot was fatally shot by ES-02. The last remaining Partisan exited the ship, only to be interrogated and then executed by Crosshair when she refused to disclose Saw's location.
Crosshair then intended to execute the refugees, but ES-01 intervened, arguing that they should be taken prisoner instead. Crosshair countered that such action was contrary to their orders, to which ES-01 responded by suggesting they disregard their orders. Crosshair promptly executed him for insubordination and instructed ES-03 and the remaining troopers to complete the mission, which they reluctantly carried out, resulting in the death of all the refugees. Upon their return to Kamino, Tarkin expressed satisfaction, acknowledging the potential of their initiative.
On Bracca, scavengers detected intruders aboard a Venator-class Star Destroyer undergoing dismantling. Admiral Rampart dispatched the squad to Bracca with instructions to eliminate the members of Clone Force 99. ES-03 and several squads of stormtroopers arrived on Bracca. ES-03's scanner malfunctioned, which he attributed to atmospheric interference. Crosshair clarified that their communications were being jammed. They proceeded to set a trap, manipulating Clone Force 99's leader, "Hunter," into leading his team towards the artillery deck, where they were cornered by Crosshair's squad and a squad of stormtroopers. Following a brief exchange, "Tech," a member of Clone Force 99, managed to activate the ship's cannons, violently propelling ES-03, ES-02, and Crosshair backward. Their accompanying squad of stormtroopers was eliminated, and ES-03 narrowly avoided being crushed by the collapsing artillery deck.
Clone Force 99 eventually escaped, although Omega was abducted by Cad Bane until her rescue on the planet of Bora Vio.
ES-03 was present during the escalation of the Free Ryloth Movement. He witnessed Cham Syndulla's attempts to persuade the Twi'leks to disarm and embrace peace. However, this peace was short-lived. When Gobi Glie, Serin, and Hera Syndulla attempted to smuggle weapons onto the planet, Crosshair tracked and shot down their transport. ES-03 and his squad subsequently arrested them for treason. They were transported back to the capitol in a HCVw A9 turbo tank with BARC speeder escorts. The convoy was attacked, and Hera was temporarily freed. However, Crosshair shot Orn Free Taa, and Admiral Rampart placed the blame on Cham. ES-03, the Elite Squad, and several stormtroopers landed in LAAT gunships to apprehend the attackers. Nevertheless, Hera and her C1-series astromech droid companion Chopper managed to escape.
Subsequently, ES-03 participated in the unsuccessful search for Hera Syndulla.
Hera, Omega, Tech, and "Wrecker" launched an assault on the Imperial doonium refinery, creating a diversion while Hunter and CT-1409 "Echo" rescued Cham and Eleni Syndulla. However, Crosshair recognized the diversion and ordered his squad to remain and prevent the prisoners from escaping. They would have succeeded if Captain Howzer had not intervened by informing the escaping prisoners of the impending trap. He then attempted to reason with the clone troopers, reminding them that they were now suppressing the people they had sworn to protect. His words inspired several troopers to lay down their weapons, but Crosshair ordered ES-03 and the remaining troopers to arrest the traitors, which they complied with.
Crosshair obtained permission from Rampart to pursue Clone Force 99, after Rampart witnessed their capabilities during the destruction of the doonium mine. This pursuit proved fruitless until Hunter was captured on Daro by clone commandos.
Following Hunter's capture, he was taken back to Kamino to serve as bait for the remaining members of Clone Force 99. Utilizing Hunter's comlink, Crosshair successfully lured Hunter's brothers to attempt a rescue. ES-03 and the Elite Squad surrounded the entrance to the Tipoca City Training Facility, forcing Clone Force 99 to surrender their weapons. Crosshair offered Hunter's squad a second chance, urging them to join the Empire. He instructed the Elite Squad to stand down, but the Elite Squad, having received orders from Rampart to monitor Crosshair, refused. Crosshair then executed a precise ricochet shot, which bounced off reflectors and killed all four Elite Squad Troopers, including ES-03.
ES-03 was a human male characterized by his darkish complexion, blond hair, and brown eyes. He voluntarily joined the Imperial Military. Although he was hesitant to execute civilians, he complied after Crosshair killed ES-01, adhering strictly to orders thereafter, such as when Crosshair instructed him to target a kid. His unwavering loyalty to the newly established Empire ultimately led to his demise.
Like all members of the Elite Squad, ES-03 wore a modified set of Phase II clone trooper armor, featuring a black color scheme with a green visor on the helmet. He wielded a DC-15A blaster carbine in combat. Additionally, he carried a datapad equipped with a built-in scanner.
ES-03 made his debut in the animated television series Star Wars: The Bad Batch. His voice was provided by Ness Bautista.