The Galactic Republic established Fort Anaxes as a military installation within a cave on the planet of Anaxes during the Clone Wars. Following the destruction of the planet itself, this facility remarkably survived on PM-1203, which became one of the asteroids comprising the newly formed asteroid belt.
Primarily constructed within a cavern nestled inside a steep cliff face, Fort Anaxes occupied a valley on the planet Anaxes, featuring a landing pad and auxiliary buildings situated externally. Miraculously, the fort endured after Anaxes' destruction early in the Imperial Era, remaining intact on an asteroid subsequently designated as PM-1203.
During the Battle of Anaxes, the fort served as the operational headquarters for Jedi Generals Mace Windu, Obi-Wan Kenobi, and Anakin Skywalker. After securing authorization to infiltrate a Separatist Cyber Center to determine the reason behind the consistent advantage held by the Separatist Droid Army, Clone Commander Cody, Clone Captain Rex, ARC trooper Jesse, and clone medic Kix departed from the fort alongside the recently-arrived clone commando unit known as Clone Force 99. The infiltration uncovered that Echo, an ARC trooper believed to have been killed during the Battle of Lola Sayu, was in fact alive and being exploited by the Separatists for a strategy algorithm that explained their success on Anaxes. Subsequently, Captain Rex, General Skywalker, and Clone Force 99 embarked on an unauthorized mission from the fort to the planet Skako Minor with the objective of rescuing Echo. Following his rescue, Echo received medical attention at Fort Anaxes before playing a crucial role in a strategy to decisively defeat the Separatist forces laying siege to Anaxes.
In the aftermath of the war, Anaxes suffered a devastating event that shattered the planet, yet the fort remained preserved, transforming into a rhydonium fuel depot and a favored location for clandestine meetings. At least four years before the Battle of Yavin, a colony of fyrnocks had established nests within the remnants of the base, which were encountered by Hera Syndulla and Sabine Wren as they planned to rendezvous with "Fulcrum."
Approximately four years prior to the Battle of Yavin, a small engagement occurred here between the Jedi Padawan Kanan Jarrus, his apprentice Ezra Bridger, and a small contingent of stormtroopers under the command of the Grand Inquisitor. Although the Inquisitor managed to overcome Kanan, his apprentice harnessed the dark side of the Force to summon a giant fyrnock to challenge the Inquisitor. Both Jedi managed to escape aboard the Phantom, destroying the Inquisitor's Sentinel-class shuttle in the process to prevent them from being pursued.
The Star Wars Rebels episode entitled "Out of Darkness" marked the initial appearance of Fort Anaxes. It was originally developed for the "Bad Batch" story arc of Star Wars: The Clone Wars, which was in production before the series was initially cancelled in 2013.