30 years ago this May, Heir to the Empire, by Timothy Zahn, hit bookshelves. It was the first in what became known as the Thrawn trilogy, and represented a post-original trilogy adventure for Luke, Han and Leia. In the process, it created a sea of changes in the Star Wars franchise. Without it, not only would Legends content have been far sparser, but in-canon movies and TV shows might look very different as well.

Zahn’s work wasn’t the first of its kind, nor did it introduce what came to be known as the Extended Universe. What it did was achieve a form of mainstream popular success at a time when Star Wars was focusing more on niche markets, such as comic books and role-playing games. It did so by acting as a catalyst for material from previous properties, which created an intense amount of synergy in the process. The result was a shared creative universe on a scale large enough to draw mainstream attention.

Related: Star Wars: How Heir to the Empire Brought the Thrawn Trilogy to Comics

It Was The Right Project at the Right Time

Thrawn and Darth Vader in Star Wars: Thrawn Alliances

Star Wars was in something of a fallow period in the late 1980s. The original movie trilogy had come and gone, and George Lucas was tentative about when and where he might develop more chapters to the saga. A few novels had been released early in the franchise's life, while TV shows were limited to Saturday morning fare and family-oriented specials like Ewoks: The Battle for Endor. None of these were on the pop culture radar by the time the Thrawn novels were released.

Fans instead looked for licensed properties that had sprung out of the film’s hugely successful toy lines. West End Games released a tabletop role-playing game in 1987, while Dark Horse Comics began a successful series of comic book adaptations in 1981. Each of them did something that expanded the potential of the Star Wars universe, a potential that Zahn was able to take full advantage of.

The RPG facilitated a further fleshing out of the universe, not just in terms of history and specific locations, but also in the kinds of characters it represented. Suddenly, fans could imagine Star Wars stories that didn’t involve Luke and Leia and exploring planets like Dantooine and Sullust that never appeared in the films. The game required Lucasfilm’s approval on all content, so it never left Lucas’s creative control, but the details it provided served as a de facto world bible, including names, cultures and biological specifics that had yet to be defined.

From the Dark Horse Comics came the notion of moving the canon characters forward in time. Earlier novelizations and comics had largely focused on the period of the original movie trilogy itself. The comics jumped ahead a few years and made it clear that just because the Emperor was dead, it didn’t mean the story was over. And like the RPG, the comics could develop in-universe ideas that the movies couldn’t, such as the idea of clones, which had been limited to a cryptic single line in Star Wars: Episode IV – A New Hope.

Zahn’s work was cut from the same cloth. When he first began writing the novels, he famously received a collection of the West End Games supplements to use as reference. He subsequently utilized a good deal of the existing in-universe content, and while his story was original, it followed the basic template of the comics in order to move beyond the events of the original trilogy. The success of the comics, which could be released more quickly than the novels, provided leeway for him to explore such notions more vigorously.

Related: Star Wars: Why Mandalorians Hate the Jedi

A Shared Universe Became More Concrete

Zahn's platform established commonality and a shared universe in ways that Star Wars simply hadn’t seen before. Ideas and terms became cemented over multiple texts. Rodians were called Rodians in the RPG and novels alike, for instance, while Mon Calamari ships carried the same cultural reasons for their distinctive shapes regardless of which franchise covered them. Zahn also found ways to let the main characters grow and change while opening the door for new figures like Thrawn and Talon Kardde to exist alongside them. Perhaps most importantly, they were strong, well-written stories that captured the spirit of the movies aptly. With Star Wars as a whole comparatively quiet, they found an audience ready to return to a galaxy far, far away.

Heir to the Empire reached #1 on the New York Times Bestseller List when it was released, and the novels became massive publishing successes. That in turn opened the door for more novels and adaptations that used the same common references to further build upon the shared universe. Some have even suggested that the renewed interest in the franchise engendered by the novels prompted Lucas to begin the development of the prequels.

Regardless of the veracity of such rumors, Zahn’s creative input was felt in subsequent franchise efforts both large and small. Fans first saw the galactic capital of Coruscant in Heir to the Empire, for instance, and Zahn’s descriptions eventually made their way to full realization in Star Wars: Episode I – The Phantom Menace. Some components, such as Thrawn himself, were ported into canon wholesale, and even ideas that had to be abandoned or changed still exerted influence. The whereabouts of Luke’s original lightsaber, for instance, was a key plot point in the Thrawn trilogy long before it arrived in Star Wars: Episode VII – The Force Awakens.

Perhaps most importantly, the books helped inspire the next generation of Star Wars creators who saw in it all the possibilities that the franchise could take. They have heavily influenced The Mandalorian, which is set during the same time period and covers a nascent Republic still battling the remnants of the Empire. Dave Filoni was also a major factor in Thrawn’s entrance in Star Wars: Rebels. Stepping outside of canon, the trilogy paved the way for Legends concepts like Star Wars: Shadows of the Empire and Darth Bane, as well as a workable means of intersecting canon and Legends content. Like A New Hope itself, the novel trilogy came along at just the right time to shake things up and remind everyone that Star Wars didn’t have to end with a single trio of movies.

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