Hosnian Cataclysm

Following the Galactic Civil War, the Galactic Empire suffered defeat at the hands of the New Republic, the governing body established by the Alliance to Restore the Republic after the Emperor's death during the Battle of Endor. The Empire formally ratified the Galactic Concordance with the Republic, which restricted the remaining Imperial forces to their territories within the Core Worlds and the Inner Rim. However, the surviving elements of the Imperial Starfleet retreated into the Unknown Regions, eventually coalescing into the First Order. This successor organization aimed to dismantle the New Republic and impose order upon the galaxy. As part of their strategy, the First Order secretly assembled a fleet in the Unknown Regions and developed a new superweapon known as Starkiller Base. This weapon, capable of destroying entire star systems, was designed to strike from a concealed and clandestine location. The creation of Starkiller represented the culmination of the Old Empire's research into dark energy translations and hyperspace tunneling, serving as a successor to the earlier DS-1 Death Star Mobile Battle Station and DS-2 Death Star II Mobile Battle Station superweapons.

During the nascent conflict between the First Order and the Resistance, Supreme Leader Snoke, the leader of the First Order, viewed Luke Skywalker as a significant threat to the First Order's objectives. Snoke feared that Skywalker, the last Jedi, might return from his self-imposed exile following the destruction of his new generation of Jedi and assist the Resistance, potentially leading to the resurgence of a new Jedi Order that could challenge his power. Kylo Ren, Snoke's apprentice, initially failed in his attempts to locate the final piece of a map needed to find Skywalker. Meanwhile, General Armitage Hux, the commander of Starkiller Base, advocated for using the weapon to destroy the Republic and eliminate what he considered an illegitimate and ineffective government. Hux argued that without the Republic, the Resistance would cease to be a threat. Snoke concurred and authorized the weapon's use.

Following Snoke's orders, Hux made preparations for Starkiller to fire upon the Hosnian system, located in the Core Worlds and serving as the capital of the New Republic. Once the weapon was ready, Hux delivered what amounted to a Neo-Imperial declaration to the assembled legions of stormtroopers under his command, who had gathered to witness the weapon's destructive power. Hux proclaimed that this day would mark the end of the New Republic and, ultimately, the Resistance, representing the culmination of the troops' efforts. He then ordered the weapon to be fired, unleashing massive energy beams across the galaxy towards the Hosnian system. Upon arrival, these beams obliterated the system's celestial bodies, including Hosnian Prime. The destruction of Hosnian Prime, the Republic's capital planet, also resulted in the destruction of the Galactic Senate and the Home Fleet of the New Republic Defense Fleet. Casualties on Hosnian Prime included Chancellor Lanever Villecham and Korr Sella, a Resistance envoy sent by General Leia Organa to warn the Senate about the First Order—a warning that arrived too late.

The destruction of the Hosnian system was visible throughout the galaxy, causing widespread terror and shock among countless worlds unaware of the unfolding events. The renowned smugglers Han Solo and Chewbacca, along with the defecting stormtrooper Finn, witnessed the system's destruction from Takodana in the Mid Rim. This sight caused confusion on Takodana, but Finn explained to Solo and Chewbacca that the First Order was using Starkiller to destroy the Republic capital. Iden Versio, a former Imperial and member of Inferno Squad, also observed the event from her home planet of Vardos. Resistance member Shriv Suurgav, who was also present, immediately recognized the First Order's involvement but struggled to understand their actions until he and Versio were captured by First Order officer Gideon Hask. While Shriv was horrified, Hask described the destruction as a thing of beauty.

On Castilon, Kazuda Xiono and Torra Doza watched a First Order broadcast of the event. As a native of Hosnian Prime, Xiono was devastated, fearing the loss of his family and friends. However, his family was off-planet and survived the attack. Xiono's father and mother attempted to contact him for days.

The destruction of the Hosnian system created a significant disturbance in the Force, which Organa immediately sensed on D'Qar, nearly collapsing from the overwhelming volume of deaths.

Following the obliteration of the Hosnian system, the war intensified, prompting the Resistance to conduct a reconnaissance mission on Starkiller Base to gather information about the First Order's weapon. By tracing the path of the phantom energy beam, the Resistance located Starkiller, and Organa tasked Black Squadron with devising a method for launching a reconnaissance mission on the base.

Jessika Pava designed a stealthy recon pod that would be towed into the Starkiller Base system by a T-70 X-wing starfighter. The pod would passively skim the base's atmosphere, collect data, and then be retrieved by the X-wing. While Pava intended to pilot the pod, Temmin Wexley volunteered, with his wife Karé Kun piloting the X-wing. The recently married couple wanted to spend as much time together as possible, fearing the potential annihilation of the Resistance.

The reconnaissance mission was successful, although Wexley barely escaped Starkiller Base's atmosphere, sustaining damage and transmitting the data to his wife, revealing his location to the First Order. Despite this, she managed to recover his damaged pod by securing it between the S-foils of her X-wing, bringing it back to D'Qar. However, this also allowed the First Order to discover the location of the Resistance base.

With the Resistance base located, a plan was devised to destroy Starkiller before it could target D'Qar. Finn, Solo, and Chewbacca were sent to disable the shields, while Commander Poe Dameron led a starfighter assault on the base's thermal oscillator, which contained the energy drained from stars to power the weapon. The Resistance successfully destroyed the weapon, but at the cost of several lives, including Solo and numerous starfighter pilots.

The Hosnian Cataclysm triggered a complete transformation of the galactic order, effectively ending the New Republic's existence or functionality. Although the New Republic never achieved the size or influence of the Galactic Republic at its peak, it had been the dominant power since the Battle of Jakku. With its political structure and primary fleet destroyed, the First Order established itself as the leading power in the galaxy, possessing the resources to conquer it. Systems and planets tempted by the First Order's promises of security quickly surrendered, while others were taken by force. Some senators, such as Hosnian Prime's Hamato Xiono, survived the destruction of the Senate, as did several military units. However, the remaining task forces were disbanded by the senators, who redirected the last of the Republic fleet to protect their homeworlds from the First Order.

Before the cataclysm, historian Chalm Plesk had traveled to Hosnian Prime to advocate for the publication of The Last War Against the Galactic Empire: On Deployment with the New Republic Fleet, which covered the return of Grand Admiral Thrawn to the galaxy. The book had been blocked by military figures, and Plesk's death left it unpublished.

At least one group of former New Republic senators who survived the Cataclysm were captured by the First Order and held on a First Order space station, along with pirates and smugglers. During a Resistance mission, Poe Dameron and Finn discovered these captured senators while escaping the station. Finn decided that prioritizing their mission and informing Leia about the senators upon their return was more important.

More than a year after the Cataclysm, the Resistance defeated the First Order and the Sith Eternal with the help of a Citizens' Fleet.

The destruction of the Hosnian system was portrayed in the 2015 film Star Wars: Episode VII The Force Awakens, the initial installment of the Star Wars sequel trilogy.

Director J.J. Abrams believed that including the scenes of Maisie Richardson-Sellers's Korr Sella could have improved the sequence and elicited a stronger emotional response. Abrams initially filmed a scene where Leia Organa tasked Sella with warning the Galactic Senate about the First Order, but deleted it from the final cut, agreeing with writer Michael Arndt that Leia's reintroduction would be more impactful through Han Solo's perspective on Takodana.

Pablo Hidalgo, creative executive of the Lucasfilm Story Group, suggested that the immediate visibility of the Starkiller Base blast from Takodana was due to a "sub-hyperspace rip side-effect" created by Starkiller.