The Battle of Naboo was a major engagement between the Republic and the Fist of Justice near the end of the Clone War. It was also the last battle the Fist of Justice participating before isolating itself on Taldornadi and leaving the war.
Date: 19 BBY
Location: Throughout Naboo; primarily outside of Theed and in and around the Fist of Justice HQ.
In 20 BBY, not long before the Battle of Telmaros, the Fist of Justice set up a secondary base on Naboo, to be used should Telmaros fall, which it did shortly after. Overseeing the Naboo base was Darth Miikan, the Dark Jedi apprentice of Lord Nihalis. However, this base remained for a while a secret to the Naboo and thus to the Republic. In very early 19 BBY, rumors of it began to spread and Naboo was cut off from communication by the Fist of Justice via satellites orbiting the planet. Eventually word of this reached the Republic and Jedi Knight Maran Teesa was sent to investigate. Miikan attempted to stop him informing the Jedi Council of Naboo's situation but he failed and soon two Republic legions, led by Jedi Masters Cato Gisera and T'ra Saa, had reached the planet. Their landed was uninhibited for the Fist's fleet was still secretly gathered at Taldornadi, unbeknownst even to Miikan.
The Republic force gathered around Theed but could not immediately proceed further as the exact location of the Fist of Justice base remained unknown. Word soon reached them that the Gungans had been infiltrated and were near persuaded to go to war with the Republic and Naboo. An alliance between the Fist and the Gungans would be dangerous as the former could bolster its own small force by providing advanced weaponry to the large army of the latter. Master Gisera decided to travel to Otoh Gunga and sort the situation out. While he was away, the Fist of Justice moved its forces to attack Theed. Not wanting to risk the city, Teesa and Saa decided to hold the battle out on the fields, despite holding less of an advantage there. Even so, the battle was a decisive victory for the Republic.
In Otoh Gunga, Gisera was received by the Gungans, who appeared to have no connection to the Fist of Justice. After a failed assassination attempt, he learned otherwise. After more investigation, Cato tracked down FoJ agent Mardullin Bosiff, who had been tasked with setting the Gungans against the Naboo and getting them to ally with the FoJ. Bosiff proved no match for Gisera and was killed by him. The next day, Gungan leader Boss Nass was assassinated. A chase ensued between Gisera and the killer, who was the same assassin who had tried to eliminate him: Bestine Holvin. Gisera was unsuccessful this time and Holvin escaped and made it off-planet.
Shortly afterwards, the Fist of Justice main base was discovered and the Republic moved its forces to that area. Their first attack, however, was rushed and was completely unsuccessful, and in fact set them back several weeks. T'ra Saa was at the head of the main attacking force but her group was ambushed by a contingent from the Blood Corps and other soldiers, and Saa was captured and taken off-planet to Lord Nihalis on Tartania and was killed by him there. Meanwhile, the recently returned Gisera battled Miikan but was unable to kill him and Teesa's forces on the other side made little headway either.
The siege remained prolonged for some time, but eventually another attack was mounted, this one more successful. Gisera's troops successfully breached the compound and Miikan was killed by Teesa. The Fist of Justice headquarters on Naboo, its last outpost outside the Unknown Regions, had been eliminated. The Republic victory was marred some as Order 66 was initiated mere days after the battle ended and Master Gisera was killed and Teesa fled off-planet. Theed was quickly occupied by the new Imperial army.