Hosnian Cataclysm

"Today is the end of the Republic! The end of a regime that acquiesces to disorder! At this very moment, in a system far from here the New Republic lies to the galaxy while secretly supporting the treachery of the loathsome Resistance. This fierce machine which you have built, upon which we stand, will bring an end to the Senate! To their cherished fleet! All remaining systems will bow to the First Order! And will remember this... as the last day of the Republic!"

- General Artimage Hux moments before destroying the Hosnian System The Hosnian Cataclysm was a major event that occured sometime during the First Order-Resistance Conflict in Star Wars: Episode VII The Force Awakens. It was the active destruction of the Hosnian System, the capitol of the New Republic, at the hands of the First Order with their superweapon Starkiller Base which has the potential to destroy entire star systems.

The event shocked the galaxy as the entire Hosnian System was destroyed in one single strike destroying the Galactic Senate and a large portion of the New Republic Starfleet as well. The destruction was seen from all over the galaxy such as the planet of Takodana.

Background
Towards the end of the Galactic Civil War, the Galactic Empire was on the verge of defeat as the Alliance to Restore the Republic had reformed into the New Republic and began to bring down the empire following the death of the emperor at the Battle of Endor. Eventually following the end of the Battle of Jakku, the Galactic Empire had signed the Galactic Concordance with the Republic limiting the remnants of the empire to the Core Worlds and Inner Rim and would eventually dissolve shortly afterwards. Remnants of the Imperial navy however, had refused to accept the concordance and instead fled into the Unknown Regions and established the First Order, a successor faction with the goal of destroying the New Republic and restoring the empire once more.

Following the formation of the First Order, they would eventually go one to construct Starkiller Base, a superweapon capable of destroying whole star systems and was the successor to the Death Star and the Death Star II. Following the beginning between the First Order and the New Republic-backed Resistance, Supreme Leader Snoke had feared that Luke Skywalker, who was living in exile, could potentially return to fight on behalf of the New Republic and avenge his fallen Jedi and initiate the return of the Jedi to the galaxy. To prevent this from happening, General Hux had suggested that the First Order use Starkiller base to destroy the New Republic citing that they're too weak to govern the galaxy and he was given permission to do so.

The Cataclysm
After getting permission to do so, General Hux had began to mobilize the weapona and aimed it towards the Hosnian System, the capitol of the New Republic. He then adressed the armies of the First Order gathered to witness the full power of the weapon and announced that the Republic would be destroyed and that all systems woukd bow to the First Order before giving out the order to fire the weapon. A massive energy beam was then fire and headed straight towards the Hosnian System. There, the system's planets would all be destroyed one by one until Hosnian Prime was hit last. The laser was seen by the people of Republic City, the planet's capitol, and they stared in horror as they were all obliterated as the planet was destroyed along with both the senate and much of the New Republic starfleet.

The destruction was witnessed by many off world, including famed smugglers Han Solo and Chewbacca as well as ex-stormtrooper defector Finn on Takodana. Finn then went to Solo and told him that it was the Republic that was hit and destroyed. Amongst the many that were killed in the cataclysm were Korr Sella, and envoy of General Leia Organa to warn the senate of the First Order and Lanever Villechham, the Chancellor of the New Republic.

Aftermath
Following the destruction of the Hosnian System, the Resistance had began to mobilize their forces and prepare for further conflict knowing that their base was soon to be the next target. Finn, Solo, and Chewbacca went on a solo mission to infiltrate the shut down the shields protecting Starkiller Base and save Rey from First Order captivity. After their mission was a success, Commander Poe Dameron lead an assault against the base and eventually was able to destroy the planet and end the threat of planetary annihilation once more.