The Imperial-class Star Destroyer (ISD), commonly called the Imperial Star Destroyer or Impstar, represented a line of enormous, dagger-shaped capital ships. These vessels served within the Imperial Navy of the Galactic Empire and, subsequently, the naval branch of the First Order. Designed as the next generation after the Venator-class and Imperator-class Star Destroyers, the line encompassed three distinct variants: the Imperial I-class, the Imperial II-class, and the Interdictor-class.
At its peak, the Empire maintained a fleet of 25,000 Star Destroyers, distributing twenty-four to each of the Empire's 1,024 Sector Groups. The Imperial-class became the mainstay of the Imperial Navy, tasked with pursuing Rebel Alliance forces, enforcing blockades on rebellious planets, and acting as mobile launch platforms for planetary invasions.
The Imperial-class Star Destroyer followed in the footsteps of both the Venator-class Star Destroyer and the Imperator-class Star Destroyer, both of which were utilized by the Galactic Republic during the Clone Wars.
As the initial version of the Imperial-class family, the Imperial I-class Star Destroyer was regarded as "the face of the Imperial Navy" and stood as one of its most formidable warships. As one of the most ubiquitous ships within the Empire's naval forces, a single Imperial I-class possessed the capability to bring an entire world to heel or devastate it through orbital bombardment. A single battle group featuring an Imperial I could effectively control an entire sector.
The Imperial II-class Star Destroyer represented an advancement over the original Imperial I-class. While visually very similar to its predecessor, the Imperial II-class incorporated several important improvements. These included a communications tower positioned between its two deflector shield generator domes instead of a tractor beam targeting array, a greater amount of weaponry, a strengthened hull, and more sophisticated deflector shields.
The Interdictor-class Star Destroyer was a specialized variant of the Imperial-class, designed for the role of an Interdictor. In contrast to the Imperial I-class and Imperial II-class, the Interdictor-class Star Destroyer featured a unique command structure and was equipped with four spherical gravity well projectors. These projectors were capable of generating a powerful artificial gravity well, creating an interdiction field. This field could prevent vessels from entering hyperspace and force ships out of hyperspace as well.
The Imperial-Star Destroyer superseded the smaller Venator-class utilized by the Galactic Republic during the Clone Wars and became the primary star cruiser of the Galactic Empire. Its design drew heavily from the Imperator-class Star Destroyer, which debuted towards the end of the Clone Wars, but saw only limited deployment before the end of the war.
During the height of its influence, the Empire had more than 25,000 Star Destroyers in service. The distinct shape of the Imperial-class struck fear into the soldiers of rebellious factions, and the name of a Star Destroyer was often preceded by the ship prefix ISD (representing Imperial Star Destroyer). In a communication to an admiral, Senior Commander Alecia Beck made reference to the ISD Vehement.
Approximately thirty years following the Battle of Endor, the First Order, the Empire's successor, introduced the new Resurgent-class Star Destroyers to replace the aging Imperial-class, incorporating design principles derived from the highly regarded and sought-after vessel.
According to J.J. Abrams, the director of Star Wars: Episode VII The Force Awakens, his original storyboarded concept involved opening the film with New Republic vessels towing a disabled Imperial-class Star Destroyer into the gravitational field of Jakku. These scenes were intentionally designed to mirror the famous opening sequence of A New Hope. The wreckage, after the crash, was intended to be scavenged by Rey. Although this sequence was removed and replaced with the attack on Tuanul, animator Tim Grey recreated the original opening sequence in a YouTube video that was uploaded on February 4, 2018.
While working on the Imperial-class Star Destroyers for Rogue One: A Star Wars Story, model maker John Knoll consulted Star Wars: Incredible Cross-Sections to ensure that the internal details visible to the audience were consistent with established Star Destroyer lore.