Siward Cass was a human male bureaucrat and military officer who served as a major and chief under the Galactic Empire, the successor state of the Galactic Republic. By the early stages of the Galactic Civil War, Cass was stationed on the DS-1 Death Star Mobile Battle Station, the Empire's planet-killing superweapon, serving as an aide to the station's commander, Grand Moff Wilhuff Tarkin.
Around this time, Cass attended a meeting of the Joint Chiefs, in which various high-ranking military officers debated the purported threat that the Alliance to Restore the Republic posed. Shortly thereafter, the captive Princess Leia Organa of Alderaan lied and told Tarkin that the rebel's hidden base was on Dantooine. When it was discovered that, while there had been a base on Dantooine, it had been deserted for some time, Cass delivered the news to Tarkin.
Fifteen years into the Emperor's reign, the human male Siward Cass held the Imperial rank of major, and the officer served as an aide to Grand Moff Wilhuff Tarkin, governor of the Outer Rim Territories. At the time, there were rumors that Commandant Brendol Hux had created a secret society within the Arkanis Academy. On Tarkin's order, Cass transferred Lieutenant Chiron from the Academy for Young Imperials on Lothal to Arkanis so he could investigate the matter. The major notably made sure that Chiron's code cylinder would give him access to Area Null, a restricted part of the academy where the Empire ran a number of secret programs.
Siward Cass was still serving under Tarkin during the Galactic Civil War, which pitted the Empire against Alliance to Restore the Republic. At this time, he was a Chief. Shortly before the Battle of Yavin, the Imperial Army officer attended a meeting on board the Death Star in which he witnessed Admiral Conan Antonio Motti and General Cassio Tagge argue about the station's power, before the Sith Lord Darth Vader Force choked Motti. He later reported to Tarkin that the planet Dantooine was not the location of the main Rebel base. Not too long afterward, the Battle of Yavin commenced, with the Alliance destroying the Death Star battle station.
Cass's rank insignia
Siward Cass used the Imperial Military's standard-issue olive colored uniform consisting of an officer's tunic, a pair of flared pants, a black utility belt, and a pair of black durasteel-toed boots. He also wore a single row rank insignia plaque of four yellow tiles followed by two red tiles.
Siward Cass first appeared portrayed by English actor Patrick Jordan in the 1977 original Star Wars film Star Wars: Episode IV A New Hope, the first installment of the original trilogy. Though unnamed in the movie itself, he was referred as "Cass" in Alan Dean Foster's novelization. Jordan got the part of Cass in A New Hope through his friendship with Alec Guinness, who portrayed Obi-Wan Kenobi and whom had worked with Jordan for The Old Vic company in the 1940s. However, Jordan shared Guinness' contempt for the film, dubious about the film's prospects.
Although Cass was sometimes identified as a general by fan-created sources, he was initially only referred to in canon as "Imperial Officer Cass" or "Officer Cass," and his exact rank long remained unknown. Unlike most characters whose names are known in the script, Officer Cass did not have an entry in the StarWars.com official Databank.
In 2013, Cass was eventually given the first name "Siward" and the rank of "Chief" in both the Death Star Owner's Technical Manual and the article The Death Star Coup, written by Jason Fry for the Special Edition 2014 of the Star Wars Insider magazine. According to Chris Trevas, one of the co-authors of the Technical Manual, Cass was given that rank because his insignia plaque was the same one as Moradmin Bast's, who was first identified as "Chief Bast" in the Star Wars Customizable Card Game Premiere Limited expansion set. Fry chose the character's first name as a nod to William Shakespeare's play Macbeth, which featured the character of Siward, Earl of Northumberland, general of the English forces.