They are most notable for their massive size and overwhelming fire power, capable of overpowering enemy ships forcing them to either surrender or be destroyed with no alternatives. At 1,600 meters (5,200 ft) long, Imperial Star Destroyers were armed with turbolasers, ion cannons, and tractor beam projectors. They could carry over a fleet of Imperial TIE Fighters and numerous ground forces, such as Stormtroopers, Walkers, and Shuttles.
The Empire's awesome wedge-shaped Imperial-class Star Destroyers formed the core of the Imperial Navy. True marvels of starship engineering, Star Destroyers were 1,600 meters and had over one hundred weapon emplacements for deep space combat.
The ship class began life as the Imperator-class Star Destroyer, introduced in limited numbers by the Galactic Republic in the last months of the Clone Wars. Upon Imperialization, the Imperator widely replaced the older Venator-class Star Destroyer that had been the Republic's prime capitol ship during the Clone Wars.
The mere presence of such a vessel in orbit was often enough to quell uprisings on Rebel sympathetic worlds, and Star Destroyer commanders could engage whole Rebel fleets and still expect victory.
Standard Imperial Star Destroyers had sixty turbolasers for ship-to-ship combat and planetary assault. A Star Destroyer's sixty ion cannons are used to disable enemy ships in preparation for boarding. The Star Destroyer's superstructure featured an immense command tower housing essential systems, computer controls and the bridge. The command tower was topped by a pair of deflector shield generator domes.
Imperial Star Destroyers had two ventral landing bays. The aft docking bay-the main launch and landing bay for shuttles, support and cargo ships, and TIE Fighters. It connected to forward interior bays and storage sections, all of which connect to immense lift shafts. Ahead of the storage sections was the forward launch bay.
The forward launch bay was used primarily to deploy assault shuttles, walker landing barges and ground force vehicles; it also could serve as an auxiliary launch or landing bay for TIE Fighters if the main docking bay was disabled.
In The Last Flight of the Harbinger, the rebels have taken control the Imperial I-class Star Destroyer Harbinger to destroy the blockade of Tureen VII.
In TIE Fighter comics 1-3, the Imperial II-class Star Destroyer Celebrity have been defected as the independent faction led by Admiral Gratloe.
In Star Wars: Squadrons, the Star Destroyer Victorum have been captured by the New Republic in the Battle above Yavin Prime.
Imperial Star Destroyers carried planetary assault teams, with landing barges, drop ships, twenty AT-AT walkers, thirty AT-ST scout walkers, and 9,700 ground troops. For a long-term planetary occupation, the Star Destroyer could deploy a prefabricated garrison base with eight hundred troops, ten AT-ATs, ten AT-STs, and forty TIE Fighters. Full planetary invasions often required a full fleet, normally six Star Destroyers, heavy and light cruisers and carrier ships.
Despite their imposing size and reputation, however, Star Destroyers were not invincible. Once the Rebels became more of a coherent fighting force, it quickly became known that the Star Destroyers were paper tigers, with many design flaws brought on by the Empire's arrogant assumption that any resistance would be light and easily dealt with exposed. Their turbolasers turned too slowly to track small moving objects such as starfighters, and had to rely on its starfighter complement and anti-starfighter screen ships to protect it from Rebel fighters such as the X-Wing and Y-Wing. This was easier said than done, though, as Rebel starfighters tended to have shielding, warheads, and more armor than a standard TIE Fighter (Y-Wings also had ion cannons that could disable enemy fighters, causing many Imperial pilots to underestimate Y-Wings as merely free target practice), and a Mon Calamari Star Cruiser could make mince-meat of the screens and escorts. In addition, although the standard MC80 design had less firepower than a standard Star Destroyer, the MC80s had a key advantage: its shields. Mon Cal ships not only had shields that constantly recharged, but also had multiple shield generators that were located inside the ship behind heavy armor; the Star Destroyer had its shield generators inconveniently located in two large geodesic spheres above its bridge that were easily exploited by Rebel bombers.
After the Empire's defeat, Imperial-class Star Destroyers were utilized alongside more advanced models such as the Resurgent-class Star Destroyer by the First Order.
In 35 ABY, the Sith Eternal constructed a massive fleet of Xyston-class Star Destroyers called the Final Order. Sith Star Destroyers were based on the design of older Imperial I-class Star Destroyers, with key differences including a larger size, red accents along the hull of the vessel, and a large axial superlaser capable of destroying planets, which took the place of a standard Imperial Star Destroyer's main hangar space.