The Expansion Region defined a galactic zone in the galaxy, situated between the Inner Rim and the Mid Rim. This region encompassed the Ghost Nebula sector, which held the Umbara system, along with Cvetaen and Sumitra star systems. It also featured the planets Aquaris, Kerkoidia, Thustra, and Sibensko.
The Clone Wars saw the Expansion Region's planets become battle zones, a consequence of the region's positioning between the Inner Rim and the Mid Rim. On Mimban, a planet within the Expansion Region, the Mud Jumpers of the 224th Division from the Grand Army of the Republic engaged with Separatist forces. They also equipped and instructed the local Mimbanese Liberation Army, promising them liberation upon the repelled of the Separatist Droid Army.
In the year 20 BBY, [Umbara](/article/umbara], a planet within the Expansion Region, became the location of a prolonged battle involving the Grand Army of the Republic and the native Umbarans, who had allied themselves with the Confederacy of Independent Systems. Many clone troopers and Umbaran soldiers died in this conflict. Pong Krell, a Besalisk Jedi Master, led the 501st Legion during this battle, but his command was unpopular among his troops. After Krell's treason was uncovered, Dogma, a trooper, executed the disgraced Jedi for his betrayal of the Galactic Republic. Following the battle, the Republic took control of Umbara.
During the Imperial Era, the Galactic Empire, a new regime that had replaced the Republic, extended its authority over much of the Expansion Region. After the theft of Moff Wilhuff Tarkin's personal starship, the Carrion Spike, an Imperial comms officer determined that the Expansion Region planets of Aquaris and Thustra were the nearest to the ship's last known location within the sector designated LCC-4-4-7. This same officer also calculated that LCC-4-4-7 was an equal distance from the Sumitra and Cvetaen systems. Vice Admiral Dodd Rancit also proposed that the Imperial facility located on Cartao, a planet within the Expansion Region, would be the next target of Berch Teller's rebel cell.
In 10 BBY, Diles Anevi held the position of governor of the Expansion Region, while Moff Bin Essada governed the Circarpous sector from Gyndine, its administrative center. Essada gave the order for Imperial forces to strip Mimban of all its resources. In the same year, the Mimbanese Liberation Army fought against Imperial forces, who sought to exploit Mimban's energy mining resources. Han Solo served as a swamp trooper within the Imperial Army's 224th Imperial Armored Division before he deserted, freeing the Wookiee slave Chewbacca and joining Tobias Beckett's gang.
In 0 BBY, Cassian Andor, an intelligence officer from the Rebel Alliance, visited the Ring of Kafrene, a trading post located in the Expansion Region. His goal was to understand why Imperial shipments of kyber crystals were being transported across the galaxy. There, Andor met Tivik, a rebel informant, who told him that Bodhi Rook, an Imperial pilot, had defected with details about a planet-killing superweapon. Andor was then compelled to kill Tivik following the latter's injury during a clash with stormtroopers.
Following the destruction of Alderaan and the Battle of Yavin, Ciena Ree, an Imperial officer, advised Thane Kyrell, a disillusioned TIE fighter pilot, to seek employment in the Expansion Region and Outer Rim Territories after she failed to persuade him to return to the Empire. Thane later became a member of the Rebel Alliance.
In 28 ABY, the watery planet Sibensko gained a reputation as a haven for criminal activity throughout the New Republic. Its underwater city served as the base of operations for the Amaxine warriors, a militia group funded by the First Order, a surviving faction from the old Empire. This city was subsequently destroyed during a skirmish, resulting in the elimination of the majority of the Amaxine warriors.
In 35 ABY, Rey, Finn, Poe Dameron, Chewbacca, C-3PO, and BB-8 journeyed to the Forbidden Valley on the planet Pasaana in search of a Sith wayfinder that could guide them to the planet Exegol. There, they encountered Lando Calrissian, a hero of the Rebellion, who assisted them in locating Ochi's dagger, a Sith assassin, within the Shifting Mires. This dagger held information regarding the Wayfinder. However, the Resistance team was pursued by the Knights of Ren and First Order forces under the command of Kylo Ren, the Supreme Leader, who captured Chewbacca, Ochi's dagger, and the Millennium Falcon.
The Expansion Region was divided into several sectors. These sectors included the Circarpous sector, the Ghost Nebula sector, LCC-4-4-7, the Narvath sector, the Ombakond sector, and the Thand sector.