He is the Commander of the Torrent Company within the 501st Legion of the Grand Army of the Republic and Clone of Bounty Hunter Jango Fett. Commander Rex is a clone trooper of the Lucas Film Star Wars series and claims designation number CT-7567. Wearing the iconic white battle suit this new generation of Stormtrooper Leader can be seen in movies such as "Attack of the Clones" (2002), "Revenge of the Sith" (2005) and "The Clone Wars" (2008).
He is described as a reliable and exemplary soldier, considered by Anakin to be his "first-in-command". Rex is characterized as believing it his duty to not only carry out orders but also to protect the men under his command, but his belief in the Republic wavers over the course of the series.