A captain serving the Galactic Empire as a sandtrooper was part of a sandtrooper regiment within the Imperial Army's Stormtrooper Corps. This trooper journeyed to the planet of Tatooine with the mission of finding the rebel droids R2-D2 and C-3PO, who carried the Death Star plans.
Within the Imperial Army's Stormtrooper Corps, a captain of the Galactic Empire functioned as a sandtrooper within a sandtrooper regiment. During the Rebel Alliance's secret mission to the planet Tatooine in 0 BBY, the Death Star plans were in the possession of the two rebel droids, R2-D2 and C-3PO. Darth Vader, the Dark Lord of the Sith, gave Commander Praji of the 501st Legion the task of using his elite sandtrooper regiment to locate the droids on Tatooine and take back the plans.
The captain led their troopers to the Lars Homestead after learning that the Lars family had the droids. They searched the home while the captain questioned Owen Lars and Beru Whitesun Lars. The captain then discovered that Luke Skywalker, Owen's nephew, had left that morning to take the droids to their workstations. The captain dispatched a detachment to look for the nephew, assuming that Skywalker was a rebel sympathizer, but believing they would not find him. After gathering all the necessary data, the captain and their soldiers went back to Mos Eisley, while the few troopers remaining killed the couple and set the homestead on fire.