The Battle of Coruscant was a large scale conflict between the forces of the Federation of Free Planets and Dark Reach over the planet Coruscant in 145 ABY. It was a catastrophic loss for the Federation, which lost, apart from its capital, many starships. Coruscant's infrastructure was destroyed, and it took a toll on its population as well.
After Darth Cyrus' adjustments following his defeat over Cybe, Cyrus drafted a plan to destroy Coruscant. Cyrus initially called only upon the Dark Reach members, but later decided to include the Predecessors as well.
Hundreds of Dark Reach vessels left hyperspace over Coruscant, immediately engaging the many space defenses, most notably the CDS-1 defense systems, as well as several orbital defense satellites. Federation ships immediately hastened to the defense lines, but were however not fast enough to even hope and try to save the defenses, for they were long destroyed by the massive Dark Reach fleet.
Having destroyed the orbital defenses, the Dark Reach warships moved on to engage the main Federation fleet, which immediately called for back up from several of its allies. Several of its allies responded, with the first to respond being the Varino Imperium, which quickly took action.
As many Federation ships were lost in fast pace, the Varino Imperium's navy arrived in aid of the Federation. Expecting this to be still insufficent, the Federation called upon the other members of its sphere of influence, which included the Hapes Consortium, the Trandoshan Hegemony and the Order of the Vergesse, most of which responded with small but fast fleets hyperspacing to Coruscant within several minutes.
As the battle raged on, the Dark Reach, having a surprise at their sleeve, decided to call upon the Predecessors now. Darth Cyrus' vessel fired a beam of light, signaling the Predecessors to arrive. Hundreds of Predecessor war vessels arrived over Coruscant, which instilled fear in many of the Federations' sphere of influence members, causing several to flee the battle.
Several hundreds of ships remained on the Federation side, while Dark Reach ships ran into the thousands of vessels, counting the Predecessor ships as well. Federation ships rallied in formation to try and inflict as much damage as they could, figuring they can't win, attempting to make a last stand.
Several warships were boarded, including the flagship of the Arcarius Varino IV, kidnapping him in the process. Many more ships were lost in the process of the boarding on both sides, however, many more on the Federation side. With most of the Federation ships in full retreat, many Korr-model dropships went down with forces to drop forces and attack the ground.
Darth Cyrus and Darth Xaviun led the ground forces for Dark Reach. Xaviun's forces engaged the main Federation ground forces, while Xaviun's forces went secretly obliterate the Coruscant infrastructure. Cyrus' forces were joined by the ships in orbit, which started bombarding the planet's infrastructure.
A ground battle followed between the Federation and Dark Reach, with several hundreds of troops and vehicles facing off in a large scale battle between the forces of Darth Xaviun and commander Fyrus Avan. While somewhat evenly matched, Dark Reach managed to secure a victory pretty easily.
Shortly after the ground battle, Cyrus went to the Jedi Temple, fighting off several Jedi that were located within the Temple. Cyrus was later joined by his forces, which effectively joined Cyrus in destroying the Temple. Cyrus went on to destroy the Senate afterwards, with most of the other buildings by then having been destroyed by the orbiting war fleet.
The Federation evacuated its remaining forces on the planet, preparing to withdraw from the battle, only to see many transports be destroyed in the process. The remaining transports managed to dock with the warships and withdrawn from Coruscant, with several ships being destroyed before retreating. The Federation's allies withdrawn from the battle as well.
The Federation of Free Planets lost its capital, but appointed Foron as its new capital later on. The Federation lost many more forces during the battle, causing their army and navy both to become very scarce.