During the Clone Wars, Crosshair was a member of the Bad Batch, an elite group of clones called in for special missions for the Republic. On Skako Minor, Clone Force 99 helped Anakin Skywalker and Clone Captain Rex get behind enemy lines to rescue the clone called Echo, who was previously thought lost in the escape from the Citadel. But despite the successful mission, Crosshair was vocal about his dislike of regular clones, which he called "regs."

At the end of the war, Crosshair was the only member of Clone Force 99 to turn on the Jedi. On Kaller, he was prepared to kill a young Padawan named Caleb Dume for treason. His leader, Hunter, prevented the murder.

After an Imperial mission to eliminate an insurgency of Separatist droids on Onderon -- only to find organic beings just trying to survive -- the other members of the Bad Batch defected from the new Empire alongside a child called Omega. However, Crosshair remained behind to serve the Emperor and Admiral Tarkin, his inhibitor chip augmented to make him more compliant to following the orders of the new regime.

Crosshair soon became the leader of a new unit of conscripted soldiers as part of the Empire's pilot program to reduce the need for clones. Known as the Elite Squad, the small sampling of highly skilled, enlisted recruits traded their names for numbers and were tasked with neutralizing anti-Imperial insurgents throughout the galaxy. 

Crosshair caught up with his old squad on Bracca after scrappers there reported a power surge aboard a Jedi cruiser. The former Bad Batcher trapped his old friends and targeted Omega during a standoff inside the wreckage. Stalking his prey, Crosshair ordered the activation of the engines, nearly incinerating Clone Force 99 in the process. But the Batch escaped with a well-placed explosive while Crosshair and his soldiers were blown back by the energy wave.

Later, after capturing Hunter and taking him to lockup on Kamino, Crosshair lured the rest of Clone Force 99 to his aid. But the Empire had other plans. Together with his former team and Omega, Crosshair witnessed the planet's destruction by the order of Vice Admiral Rampart and his Star Destroyers. The Bad Batch were presumed dead, but together they escaped a watery grave, leaving Crosshair behind.

For several months after the disaster on Kamino, Crosshair continued to serve the Empire with unflinching loyalty. But Imperial leadership’s faith in the remaining clone soldiers was waning and on Barton IV, Crosshair became disillusioned with the Empire during a mission to secure cargo at a far-flung Imperial depot, where most of the clones assigned there had been killed. Under strict orders from Lt. Nolan, Crosshair and the depot's last surviving clone, Commander Mayday, ventured off into the cold on an ill-fated mission to recover cargo stolen by raiders. Returning to the depot without the cargo, Crosshair came to the grim realization that the clones of Barton IV had all given their lives protecting stormtrooper armor intended for their conscripted replacements. After Nolan refused to allow medical attention that could save Mayday's life, Crosshair took matters into his own hands and fired on his superior officer.

Imprisoned for his treason, Crosshair was arrested and sent to the Empire’s secret Mount Tantiss facility on Wayland. Although he managed to get an urgent message relayed to his squad, Crosshair’s resolve quickly crumbled. 

Subject to intense medical testing alongside countless other clones, Crosshair remained at the mercy of Doctor Royce Hemlock for many months, becoming more defeated with each passing day. When Omega first proposed her dreams of escape, Crosshair belligerently tried to convince her that he was a lost cause who would escape without her if given the chance. But Omega refused to give up hope, seeing through Crosshair’s tough exterior and securing the datapad that led them to freedom through the lurca hound tunnels. In a stolen shuttle, they escaped first to Lau then to the moon of Ryloth for a tense reunion with the remaining members of Clone Force 99: Hunter and Wrecker. In time, Crosshair and his brothers began mending their fractured relationship. But other clones, like the squad stationed on Teth working with Captain Rex, were less forgiving of Crosshair’s past infractions. And the experimentation on Tantiss continued to haunt him as he grappled with a tremor in his right hand that made it nearly impossible to continue his career as a sharpshooter.