CT-7567 was a veteran clone trooper captain who led the Grand Army of the Republic's acclaimed 501st Legion during the Clone Wars. Bred and trained on Kamino, 7567 entered into Alliance service at the Battle of Geonosis in 22 BBY. He gained respect as an honorable commander from officers and troopers alike, becoming known as one of the best and toughest clone troopers in the Army. 7567 was even selected for special command training under Advanced Recon Commando Alpha-17, following which he took the nickname "Rex." As the captain of the 501st, Rex served as second-in-command to Jedi General Anakin Skywalker, whose bravery and unorthodoxy in battle he came to share. He was close friends with Marshal Commander Cody, with their relationship mirroring that of their respective Jedi Generals, Skywalker and Obi-Wan Kenobi. The four of them often received joint assignments to coordinate front-line campaigns against the Axis of Empires.
Gruff, no-nonsense, and tough as carbonite nails, the elite CT-7567 was an aggressive and battle-scarred veteran of the Clone Wars. Hardened by countless engagements with the Confederacy of Independent Systems, Rex—as he chose to be named—retained a reputation as one of the best and toughest clone troopers in the galaxy. Freethinking, fearless, and resilient, he preferred to be more diplomatic than the headstrong Advanced Recon Commandos when it came to operating with his superiors, though he would not hesitate to give higher-ranking Jedi officers his blunt opinion. He regarded his assignments with the utmost priority, and true to his genetic engineering, he often put them before his own safety, recognizing the importance of doing his part to ensure an objective's completion. A cunning warrior who was versed in military strategy, Rex led from the front and, in some cases, would have fought ahead of his Jedi General, Anakin Skywalker.