Alpha – a designation originating from his designation Alpha-17, which could be shortened to A-17 – served as an Alpha-class Advanced Recon Commando within the Republic's clone army throughout the duration of the Clone Wars.
Jango Fett personally selected Alpha, alongside other clones, for specialized training intended for the most challenging operations. Consequently, the ARCs received customized gear and exhibited a degree of Jango's individual personality and independence. Due to their perceived threat, the Kaminoans placed all the ARC troopers in suspended animation.
Alpha, like the other ARCs, initially engaged in combat during the Separatist invasion of Kamino. As the droid forces of the Confederacy advanced towards the core of Tipoca City, Lama Su, the Kaminoan Prime Minister, activated the ARCs. He authorized their deployment to critical locations across Kamino in a final attempt to safeguard the planet's vital cloning facilities.
During the struggle to expel the droids from Tipoca's main armory, Alpha joined forces with Jedi Master Shaak Ti, Jedi Knight Obi-Wan Kenobi, and Anakin Skywalker, Kenobi's Padawan. When the city's clone supplies were at risk, Alpha, much to the Jedi's dismay, set the lab to self-destruct. His remark, "They grow up loyal to the Republic, or they don't grow up at all," made it clear to the Jedi that he was not a typical clone trooper. Ti expressed her wish for an alternative, and Alpha devised a plan for Obi-Wan and Anakin to collapse the transparisteel walls connecting the facility while Ti held back the ocean before they sealed the area. After the plan succeeded and the attack was successfully thwarted, Alpha deactivated the detonation sequence.
When contact was lost between Naboo and the Gungan colony moon of Ohma-D'un, a Separatist assault was feared, prompting the dispatch of Generals Kenobi and Skywalker to investigate. Kenobi, recalling Alpha's deadly effectiveness on Kamino, brought him along. Upon arriving on the surface, the trio discovered the Gungan colony in ruins, with bodies scattered as far as they could see. Before they could fully investigate the cause of the genocidal massacre, they were ambushed by the bounty hunter Durge and the Dark Jedi Asajj Ventress. Following Kenobi's instructions, Alpha accompanied Anakin to locate and destroy the bio-weapon responsible for the destruction of Ohma-D'un before it could be unleashed in Theed. It was at this time that Anakin, feeling uncomfortable simply calling him "clone," after the ARC told him his designation, gave the trooper the name "Alpha."
They not only succeeded in destroying the ships but also returned in time to rescue Obi-Wan, forcing Ventress to retreat.
Following the Ohma-D'un mission, Alpha was once more selected by Kenobi and Anakin to join them on another crucial assignment. This time, the three were tasked with leading the assault on Jabiim, an obscure world in the Outer Rim that had recently pledged allegiance to Count Dooku's Confederacy. The initial stages of the assault saw a string of victories for the Republic. However, as the relentless rain persisted, their assault vehicles became mired in the mud, turning them into easy targets for the Jabiimi guerrillas. As Republic casualties rose, the rebels, now reinforced with Separatist battle droids, intensified their attacks. The Republic suffered a major setback with the presumed deaths of Obi-Wan and Alpha while they were clearing a downed All Terrain Armored Transport.
However, neither Obi-Wan nor Alpha perished in the explosion that was thought to have killed them. In reality, Alpha had managed to rescue Obi-Wan, and subsequently, both were captured by the Separatists and taken to a secret prison on Rattatak. There, Asajj Ventress, the Dark Jedi from Ohma-D'un, attempted to extract sensitive information about Republic troop movements through physical abuse and torture, especially from Alpha. However, he only revealed his identification number, much to her frustration. Before she could obtain the information she sought, she threw him into Obi-Wan's cell. Working together, the two orchestrated an escape under the guise of a prison break. After fighting their way off Rattatak and evading Ventress with the help of Anakin and Master Ki-Adi-Mundi, they returned to the Republic and the Grand Army.
After enduring this ordeal and spending several weeks in a bacta tank, Alpha was reassigned to Kamino to train current and future generations of clone commanders. Following Anakin's earlier suggestion that he give them names, he was promoted to the rank of captain and became the lead instructor at the Tipoca City training facility. Commanders Cody of the 212th Attack Battalion, Neyo of the 91st Reconnaissance, Bacara of the 21st Nova Corps, Gree of the 41st Elite Corps, Appo of the 501st Legion, Rex of the 501st Legion, Bly of the 327th Star Corps, Faie, and numerous others were among the initial hundred to enroll in and graduate from his experimental training program, known as the ARC training program. From this first group, Alpha personally selected a few individuals and assigned them to Squad Seven, with Commanders Davijaan and Cody serving as its leaders.
Despite his responsibilities on Kamino, Alpha continued to serve in the field. He was chosen to accompany Senator Bail Organa on his tour of the Outer Rim Sieges aboard the Star Destroyer Intervention. When General Kenobi commandeered the Intervention to lead the assault on Boz Pity, Alpha prepared for another battle. During the conflict, General Grievous critically wounded Alpha, leaving him with injuries so severe that it was believed he would never walk again. As the fighting subsided, Alpha, along with the supposed corpse of Asajj Ventress, was loaded onto a medical transport and sent back to Coruscant for treatment. However, Ventress revealed herself to be alive during the journey, seizing control of the transport and ordering the pilots to take her into the unknown.
According to the commentary on the Star Wars: The Clone Wars DVD, the creators initially intended to feature Alpha-17 as the primary clone character in the Clone Wars series. However, George Lucas objected because his inclusion would result in excessive alliteration (Anakin, Artoo, Ahsoka, and now Alpha). Consequently, a different clone character, clone trooper captain Rex, was created instead.