Alpha-17, as was the case with the rest of the ARCs, first saw action with the Separatists' invasion of Kamino. As the Confederacy's droid forces pushed towards the heart of Tipoca City, the Kaminoan Prime Minister, Lama Su, activated the ARCs and authorized their deployment to hot-spots across Kamino in a last-ditch effort to save the planet's precious cloning facilities.
During the fighting to push the droids from Tipoca's central armory, Alpha teamed up with Jedi Master Shaak Ti, Jedi Knight Obi-Wan Kenobi, and Kenobi's Padawan, Anakin Skywalker. When the city's clone stocks became compromised, Alpha rigged the lab to self-destruct, much to the dismay of the Jedi. After remarking, "They grow up loyal to the Republic, or they don't grow up at all," it was clear to the Jedi that they were not dealing with an average clone trooper. Ti wished there was another way, so Alpha made a strategy for Obi-Wan and Anakin to collapse the transparisteel walls linking the facility while Ti held back the ocean before they sealed the place off. When the plan worked and the attack was successfully repelled, Alpha then aborted the detonation sequence.
When the Naboo lost contact with the Gungan colony moon of Ohma-D'un, a Separatist attack was suspected, and General Kenobi and Skywalker were sent to investigate. Kenobi, having witnessed his lethal effectiveness on Kamino, took Alpha along for the ride. When the trio arrived on the surface, they found the Gungan colony in ruins and bodies for as far as the eye could see. Before they could complete their investigation into the cause of the genocidal slaughter, however, they fell under attack from the bounty hunter Durge and the Dark Jedi Asajj Ventress. Under Kenobi's orders, Alpha went with Anakin to find and destroy the bio-weapon responsible for Ohma-D'un's destruction before it could be let loose in Theed. It was then that Anakin, uncomfortable with calling him simply "clone," named the ARC trooper "Alpha".
Battle vs. Marcus Fenix (by Tomahawk23)
No battle written
Winner: Marcus Fenix
While Alpha-17 brought in Explosives and a Blaster Rifle which were major threats to Fenix, the latter's weaponry was more effective in close and long ranges, and his higher strength, physicality and experience allowed him to overcome the clone trooper.