Question: What year was the trilogy, also known as the Heir to the Empire, from the Star Wars expanded universe written?

Context articles: Dark Force Rising
Thrawn trilogy
Star Wars: Republic
Star Wars expanded universe
Grand Admiral Thrawn
Star Wars: Darth Plagueis
Wookieepedia
James Luceno
Y-wing
Star Wars MUSH

Star Wars: Dark Force Rising is a 1992 "Star Wars" novel by Timothy Zahn, and the second book in the "Thrawn" trilogy.
The Thrawn" trilogy, also known as the Heir to the Empire" trilogy, is a series of best-selling science fiction novels written by Timothy Zahn.
 They are set in the "Star Wars" expanded universe approximately five years after the events depicted in the 1983 "Star Wars" film "Return of the Jedi".
 The series introduced several notable characters, including Mara Jade, Talon Karrde, and Grand Admiral Thrawn, one of the more notable villains in the expanded universe.
 The "Thrawn" trilogy was followed by "The Hand of Thrawn", a two-book series (1997 and 1998) also authored by Zahn.
Star Wars: Republic is an American comic book series set in the fictional "Star Wars" universe.
 The series was published by Dark Horse Comics from 1998 to February 2006.
 The series was originally titled simply "Star Wars", but acquired its "Republic" title at issue 46.
 The entire series comprises 83 issues.
 The "Star Wars: Republic" series is one of a number of comic book series set in the "Star Wars" expanded universe.
The "Star Wars" expanded universe (SWEU; formerly branded as Expanded Universe or EU) is a collective term for all "Star Wars" fictional material produced by Lucasfilm or officially licensed by it.
 This expanded universe includes an array of derivative "Star Wars" works produced in conjunction with, between, and after the original trilogy (1977–1983) and prequel trilogy (1999–2005) of films, and includes books, comic books, video games, and television series.
 Intended as an enhancement to and extension of the "Star Wars" theatrical films produced by George Lucas, the continuity of all "Expanded Universe" material was tracked by Lucasfilm, and Lucas reserved the right to both draw on it and contradict it in his own works.
Grand Admiral Thrawn (full name Mitth'raw'nuruodo) is a fictional character in the "Star Wars" franchise.
 Introduced in the 1991 Timothy Zahn novel "Heir to the Empire", he is an Imperial military commander who has taken control of the Galactic Empire's remaining forces five years after the events of the 1983 film "Return of the Jedi".
 Thrawn faces off against classic "Star Wars" characters Luke Skywalker, Princess Leia, Han Solo, Chewbacca, and Lando Calrissian in the "Thrawn" trilogy (1991–1993), but is ultimately defeated.
 He is seemingly resurrected in the "Hand of Thrawn" duology (1997–98), and his backstory is explored in various other novels, short stories, comics, and video games in the "Star Wars" Expanded Universe.
Star Wars: Darth Plagueis is a novel that is part of the "Star Wars" expanded universe.
 It was written by James Luceno, and released on January 10, 2012.
 The novel covers the later life and machinations of Sith lord Darth Plagueis, over a roughly fifty-year period pre-dating "Star Wars: The Phantom Menace".
 The novel details Plagueis' overthrow of his own master Darth Tenebrous, his work as head of a powerful banking consortium on the Muun homeworld, his discovery, recruitment and training of the teenaged Sheev Palpatine of Naboo, and the efforts of Plagueis to undermine the Galactic Republic and ensure the dominance of the Dark Side of the Force.
 The novel brings in scores of characters and locations already familiar in the "Star Wars" mythos, as well as introducing many others for the first time.
 Events depicted on-screen in "Star Wars Episode I: The Phantom Menace", are re-told in "Star Wars: Darth Plagueis", often from a perspective not shown in the 1999 motion picture.
Wookieepedia: The "Star Wars" Wiki is an online encyclopedia for information on the "Star Wars" fictional universe—including information on all the films, as well as "Clone Wars", "" and its , "Rebels", the "Star Wars" expanded universe, and any upcoming "Star Wars" material.
 It is a specialized wiki created to be an extensive encyclopedia of the "Star Wars" universe with some articles reaching up to 60,000 words, and is written almost entirely from an in-universe perspective.
 The name Wookieepedia is a portmanteau of Wookiee and encyclopedia, a pun on the name of "Wikipedia".
 The logo, too, is a visual pun showing the incomplete second Death Star as opposed to Wikipedia's incomplete "jigsaw logo".
James Luceno (born 1947) is a "New York Times" bestselling author, best known for his novels and reference books connected with the "Star Wars" franchise and the Star Wars Expanded Universe, and (with Brian Daley under the shared pseudonym Jack McKinney), novelisations of the "Robotech" animated television series.
 Luceno is also the author of several original novels along with film novelisations and other franchise tie-ins.
 He has also written for television cartoon series.
The Y-wing is a fictional Galactic Republic, Rebel Alliance and New Republic starfighter in the "Star Wars" franchise.
 They appear in "", "Star Wars Episode V: The Empire Strikes Back", "Star Wars Episode VI: Return of the Jedi", "Rogue One", , "Star Wars Rebels" TV series and the "Star Wars" expanded universe's books, comics, and games.
Star Wars MUSH (commonly referred to as SW1) is a text-based online role-playing game.
 "Star Wars MUSH" was created in May 1991 and was released to the public in January 1992.
 The game predates the majority of ""Star Wars" expanded universe" and as such largely deviates from the established "Star Wars" universe set after "Return of the Jedi".
 The game scenario system is based on the discontinued West End Games' .
 The game persisted throughout the '90s as one of the net's more successful "Star Wars"-themed MUSHes, earning a feature in "The Incredible Internet Guide to Star Wars".