ES-01 was the identifier assigned to a human male serving as an Elite Squad Trooper. He was among the initial soldiers inducted into the Galactic Empire through Project War-Mantle, an initiative spearheaded by Vice Admiral Edmon Rampart to recruit enlisted personnel. Rampart considered ES-01 and his fellow squad members to be among the most capable soldiers in the galaxy. Consequently, ES-01 was integrated into the Elite Squad, which was under the command of Clone Commander CT-9904. His life ended at the hands of CT-9904 after he refused to carry out the execution of civilians who were under the protection of rebel leader Saw Gerrera on the planet Onderon.
Almost immediately, ES-01 developed a strong dislike for Crosshair, the leader of the group. During their journey to Onderon, he even commented that Crosshair would eventually lose his position of authority. This tension persisted throughout their mission, with ES-01 attempting to assume command and persuade the squad to disregard their orders, which ultimately led to Crosshair executing him.
ES-01 was a human male living during the era marking the Galactic Republic's transformation into the Galactic Empire as the Clone Wars concluded. He was enlisted into the newly formed Imperial Military through Project War-Mantle, an initiative designed to integrate both conscripted and recruited soldiers into the military, as opposed to relying solely on clones.
ES-01 was present when Vice Admiral Edmon Rampart introduced him, along with the other members of his Elite Squad, to Grand Moff Tarkin on Kamino. Subsequently, ES-01 voiced his dissatisfaction with joining the military only to be subjected to scans by droids. He also remarked, along with his squad-mates, that the Empire provided more for him than the Republic ever had by offering payment, sustenance, and lodging.
ES-01 and his squad were placed under the command of Clone Commander CT-9904, known as "Crosshair." They received orders from Admiral Tarkin to complete Clone Force 99's assignment and eliminate Saw Gerrera and his insurgents on Onderon. During their journey to Gerrera's camp aboard their Nu-class attack/transport shuttle, ES-01 openly expressed his contempt for Crosshair as a clone and warned him that he desired his position of command.
Upon reaching Gerrera's camp, ES-01 and his squad successfully defeated the insurgents, destroying their starship and compelling the remaining survivors to surrender. However, when Crosshair instructed the squad to execute the prisoners, ES-01 objected and refused to comply, arguing that they were civilians and that the order was unjust. ES-01 commanded the rest of the squad to take them into custody, but Crosshair immediately executed him, leading the remaining squad members to hesitate before killing the civilians.
Later, when the squad returned to Kamino, Tarkin noticed ES-01's absence. However, Rampart commented that while his loss was regrettable, soldiers were always susceptible to death in battle and understood the inherent risks.
Vice Admiral Rampart considered the human male known as ES-01 to be among the "best soldiers" in the galaxy. Despite this high regard, ES-01 was willing to openly challenge authority and express his frustrations. He also publicly voiced his disagreement with orders when he believed they were wrong. Furthermore, ES-01 possessed a competitive nature and held a condescending view of Crosshair as a clone, suggesting that the Empire sought conscripts and recruits because clones were not as effective as previously believed.
Like all members of the Elite Squad, ES-01 wore a set of modified Phase II clone trooper armor, which was black with a green visor on the helmet. He carried a DC-15A blaster carbine for combat.
ES-01 debuted in "Replacements," the third episode of the first season of the animated television series Star Wars: The Bad Batch, which aired on May 14, 2021. Emilio Garcia-Sanchez is credited as the voice actor for the character.