The Mandalorian occupation refers to the Galactic Empire's control over the planet of Mandalore. Although the Empire's predecessor, the Galactic Republic, aided the Mandalorian resistance in reclaiming their homeworld, the continued presence of Republic forces on Mandalore facilitated the Empire's subsequent takeover.
During this period, the Empire established an Imperial Academy within the former Royal Academy of Government situated in the capital city, Sundari. Many Mandalorians chose to serve the Empire, with Clan Saxon explicitly pledging their allegiance to the Imperial regime. Numerous individuals enlisted in the Imperial Military, becoming Imperial Super Commandos.
Bo-Katan Kryze, initially installed as regent of Mandalore after Maul's capture, resisted Imperial authority. Consequently, she was ousted from power by Clan Saxon and replaced by Gar Saxon, who governed Mandalore as the Empire's appointed governor. Following her removal, Bo-Katan spearheaded a resistance movement aimed at liberating Mandalore from Imperial rule, receiving support from the rest of Clan Kryze.
By 2 BBY, Mandalore was embroiled in a civil war between the Mandalorian resistance and the Empire. Clan Wren joined the resistance, while Tiber Saxon succeeded Gar as governor after the latter's demise on Krownest during a skirmish there. A year later, Tiber successfully replicated the Arc Pulse Generator, a superweapon created by Sabine Wren before her involvement with the Spectres. He intended to utilize it to quell the rebellion and solidify Imperial control, but his plans were thwarted by the Mandalorian rebels, backed by the newly formed Alliance to Restore the Republic, resulting in the weapon's destruction and Tiber Saxon's death.
Towards the conclusion of the Galactic Civil War, the Empire, seeking retribution against Mandalore for its rebellion and aiming to prevent any faction from gaining control of the planet, initiated the Great Purge of Mandalore, a campaign of genocide against the Mandalorian population. Led by Moff Gideon, Imperial forces devastated Mandalore in an event known as the Night of a Thousand Tears, decimating Mandalorian recruits and destroying their military strength. In an attempt to minimize further casualties, Bo-Katan surrendered to Moff Gideon, handing over the Darksaber in exchange for the cessation of hostilities. However, this was a deception, and the purge continued, transforming Mandalore into a desolate wasteland.
During the Clone Wars, the Mandalorian terrorist group Death Watch, under the leadership of Pre Vizsla, repeatedly tried to overthrow the pacifistic New Mandalorian government headed by Duchess Satine Kryze with the intention of restoring Mandalore's warrior traditions. Under Pre Vizsla's leadership, Death Watch allied themselves with the Confederacy of Independent Systems to assist in overthrowing the New Mandalorians, who had declared Mandalore neutral during the Clone Wars. By 21 BBY, Death Watch drew the attention of the Galactic Republic following an attack on a Republic cruiser by a saboteur which, coupled with rumors that Mandalore was considering siding with the Confederacy, prompted Jedi Master Obi-Wan Kenobi to travel to Mandalore to investigate Death Watch. During his investigation, both Obi-Wan and Satine discovered the Death Watch camp, with Vizla revealing himself following an investigation to the moon of Concordia. As part of their schemes, Death Watch made two attempts on Satine's life, with an attack on the Coronet with the support of super battle droids and then on Coruscant where a Death Watch assassin was dispatched to assassinate her to ensure that the Republic would occupy Mandalore and give the needed public support to ensure the Death Watch can take over, but this also failed.
By 19 BBY, Death Watch remained steadfast in their goal to overthrow Duchess Satine, even while exiled on the moon of Carlac. There, they encountered an escape pod containing the Sith Lords Maul and his brother Savage Opress. They were taken to the Death Watch camp on Zanbar where, after recovering, Maul managed to convince Death Watch to join forces to eliminate their mutual enemies, forming an alliance that would become the Shadow Collective that would go on to include several crime syndicates; the Black Sun, the Pyke Syndicate, and later the Hutt Clan. Together, the Shadow Collective orchestrated a successful takeover of the planet, leading to Satine's imprisonment and Pre Vizsla's ascension as Mandalore's new leader, although he was later killed by Maul in a duel for leadership. Following Vizsla's death, Death Watch fractured into factions loyal to Maul and those opposing his rule, with the latter group rallying around Bo-Katan Kryze, who established a resistance movement to oust Maul.
Mandalore quickly descended into a state of civil war, pitting the Mandalorian resistance against the Mandalorian Supercommandos loyal to Maul. Fighting erupted in the capital city of Sundari, initially during a failed attempt to rescue Satine, but escalated into full-scale warfare by nightfall. During the battle, Obi-Wan, who had been captured during his attempt to rescue Satine, was freed and instructed by Bo-Katan to alert the Republic of Maul's takeover, anticipating a Republic invasion that she hoped would lead to Maul's demise. Maul remained in control of Mandalore, and the Republic eventually invaded Mandalore during the final days of the Clone Wars. The Mandalorian rebels, supported by the newly formed 332nd Division of the 501st Legion commanded by Clone Commander Rex and former Padawan/Advisor Ahsoka Tano, invaded and besieged the planet. After a prolonged battle, Maul's forces were defeated, and he was successfully captured on the eve of the execution of Order 66.