After the Battle of Jakku, a significant faction of the Galactic Empire, secretly reassembling in the Unknown Regions under the command of Grand Admiral Rae Sloane, would later serve as the foundation for the First Order's military. Its establishment had been meticulously planned decades earlier as part of Darth Sidious' Contingency strategy, which mandated the escape of crucial assets and personnel to the Unknown Regions, while the remaining portion of the Empire faced destruction. The groundwork for an Imperial resurgence was laid within the Unknown Regions, which the Galactic Empire had covertly explored and prepared.
Following Darth Sidious' demise at the Battle of Endor in 4 ABY, the Contingency, overseen by the Emperor's apprentice, Gallius Rax, initiated preparations for the retreat to the Unknown Regions. Rax amassed the majority of the Imperial Navy at Jakku, intending to lure the New Republic into an ambush and annihilate both sides.
However, Sloane killed Rax during the Battle of Jakku, and, spurred on by the dying Rax, who designated her as his successor, went into hiding with surviving Imperial vessels, along with other select personnel, into the Unknown Regions to regroup and rebuild a new Empire. By 21 ABY, the remnant had transformed into the First Order, a fascist military dictatorship determined to obliterate the New Republic. The First Order was ultimately crushed by a series of rebellions in 35 ABY.
In 19 BBY, Darth Sidious proclaimed the establishment of a new Galactic Empire to govern the galaxy. To prepare for the possibility of his death, Sidious developed a Contingency plan that would enable him to attempt to reclaim power. The Contingency dictated that the Emperor's protégé, Gallius Rax, should eliminate the weaker elements within the Empire and then withdraw to the Unknown Regions. In preparation, the Sith Lord strategically placed shipyards, laboratories, and storage facilities throughout the Unknown Regions, a monumental task that spanned decades. This undertaking was known only to Sidious' chosen few. Alongside the infrastructure, hyperspace lanes and secretly documented worlds were also established.
Immediately following Sidious' death at the Battle of Endor in 4 ABY, his Contingency plan was activated. Counselor Rax, the de facto leader of the Galactic Empire, endeavored to gather as many Imperials as possible at Jakku, successfully assembling the majority of the Imperial Navy there, with the objective of destroying as many Imperial and New Republic forces as he could.
The demise of Rax at the Battle of Jakku in 5 ABY resulted in Grand Admiral Rae Sloane assuming command of the Imperial loyalist forces. Following the Empire's defeat by the New Republic on Jakku, Imperial officials and military vessels from the Imperial fleet were compelled to retreat into the galaxy's Unknown Regions, which the Empire had secretly been exploring in accordance with the Emperor's Contingency. Sloane, along with other Imperial leaders such as Commandant Brendol Hux, guided these former Imperial officers, aristocrats, scientists, warlords, and armadas in establishing a substantial remnant of the Empire within the Unknown Regions, inadvertently fulfilling Sidious' Contingency plan by creating a clandestine stronghold there.
The loss of numerous promising commanders to the Unknown Regions contributed to Grand Vizier Mas Amedda's decision to formally cede the Empire to the New Republic and ratify the Galactic Concordance, which dissolved the Imperial government and reduced the Empire to a small state in the inner systems. Besides the inner systems' remnant, various other remnants that refused to adhere to the Galactic Concordance emerged in the known galaxy, including Gideon's Imperial remnant, Gilad Pellaeon's delegation and the Morak Imperial remnants. Grand Moff Randd also oversaw an Imperial remnant in the Unknown Regions Queluhan Nebula, where he controlled several Star Destroyers.
Having met with the Eclipse and anyone who had already arrived in the months following the Battle of Jakku, Sloane and Hux played pivotal roles in the creation of this new regime. Sloane, in particular, bore greater responsibility for perpetuating Imperial ideology than anyone else. They ensured that it would be structured along Imperial principles while also striving to avoid repeating past errors, which set them on a course toward Neo-Imperialism. The New Republic remained oblivious to the remnant in the Unknown Regions, despite circulating rumors of an Imperial-inspired menace there.
From 5 to 15 ABY, the remnant subdued the Unknown Regions as it colonized the vast expanses of uncharted space. Following years of adversity in the wilderness of the Unknown Regions, navigating through sparsely mapped star systems, the remnant eventually established a secure presence on planets that had been previously secretly charted by the Empire. The expertise of Grand Admiral Mitth'raw'nuruodo "Thrawn," a Chiss indigenous to the Unknown Regions, coupled with the assistance of hyperspace routes charted by the Attendants, aided the Empire in mapping the Unknown Regions to serve as a sanctuary for the former Imperials. Without the support of the hyperspace routes established by the Attendants, the Imperial survivors would have perished in the untamed regions of the Unknown Regions. In addition to navigational assistance, the remnant encountered secret Imperial reinforcements that had been previously stationed there by the Emperor.
The security of the Unknown Regions enabled the remnant to expand over time. Concealed behind the obscurity of the Unknown Regions and thus shielded from the watchful eyes of the New Republic, they plotted their return to power, initiating a movement to secretly rebuild their forces and fleets, financed by major corporations and utilizing hidden shipyards. In particular, the Vulpinus Nebula served as a refuge for Imperial survivors for decades after the fall of the Empire.
By 21 ABY, a clandestine alliance formed between the Unknown Regions Imperial remnant and the Corporate Sector Authority in the New Republic Era. Cooperation with the CSA provided secret funding to the remnant, and its leadership assigned High Colonel Enric Pryde to collaborate with the company. A former officer in the Imperial Navy, Pryde survived the Battle of Jakku and dedicated himself to the restoration of the Galactic Empire, although he viewed his assignment with the CSA as beneath an officer of his caliber. The codename Steadfast was assigned to him to maintain the secrecy of the remnant's connection to the CSA.
In 21 ABY, the Sith Eternal sect instructed the Jedi hunter Ochi of Bestoon to seek out their agent, Steadfast, for assistance in locating Rey, the grandchild of the Dark Lord of the Sith Darth Sidious. Despite his disdain for his assignment with the CSA and the quality of their paramilitary police, the high officer granted Ochi's request, providing the hunter with a unit of CSA troopers despite objections from his second-in-command, Viceprex Coromun. Later that year, the First Order, a military junta and successor state to the Empire, was established by the Unknown Regions Imperial remnant. Its military branch originated from elements of the Unknown Regions Imperial remnant.
The Unknown Regions proved to be a successful sanctuary for the First Order military, enabling it to amass its strength undetected by the New Republic. The First Order ultimately succeeded in conquering vast territories within the galaxy by 34 ABY but was eventually overthrown by a series of revolts following the Resistance's triumph at the Battle of Exegol in 35 ABY.