In the year 2 BBY, a mission was launched by Phoenix Cell members to the third moon orbiting Concord Dawn. This came about after Phoenix Cell lost communication with the Mandalorian Protectors. Consequently, Fenn Rau, Sabine Wren, Ezra Bridger, and Chopper journeyed to the moon in question to investigate. Their investigation revealed that Imperial Mandalorians commanded by Viceroy Gar Saxon had assaulted the Protectors' encampment, resulting in a massacre. Working in unison, they successfully evaded the Protectors and escaped off-world. This shared experience led Rau to make the decision to align himself with the rebellion.
Back in 3 BBY, Sabine Wren, Kanan Jarrus, along with the astromech droid Chopper, executed a kidnapping of Fenn Rau, the leader of the Mandalorian Protectors. This act followed Rau's attack on a rebel delegation within the Concord Dawn system. In exchange for keeping his capture a secret, Rau instructed his Protectors to grant the rebels safe passage through the system. During his captivity, Rau received considerate treatment from the rebels, leading to interactions with Sabine, who attempted to sway him to the rebel cause.
On Mandalore, Viceroy Gar Saxon, the ruling figure, and his Mandalorian super commandos collaborated with the Galactic Empire. They were of the belief that the Empire would restore Mandalore to greatness, fostering a strained relationship with the Concord Dawn Protectors. Upon discovering that the Protectors were permitting rebel ships to utilize the system as a shortcut to circumvent Imperial sector patrols, Saxon and his followers launched an assault on the Protectors Camp situated on the third moon of Concord Dawn. They proceeded to slaughter everyone present at the camp, failing, however, to locate Rau, who was their primary objective.
Following the loss of contact with the Protectors, Hera Syndulla and rebel commander Jun Sato convened Rau and Sabine for a briefing. While Sato and other rebel leaders suspected a trap by the Protectors, Rau suspected foul play against his followers and requested permission to investigate. Hera granted his request but dispatched Sabine, Ezra Bridger, and Chopper to monitor him. The rebels, accompanied by Rau, traveled to the Concord Dawn system aboard the repurposed Sheathipede-class shuttle Phantom II.
During their voyage to Concord Dawn, Fenn Rau managed to break free from his restraints and stunned both Sabine and Ezra. After securing them with cuffs, he left the ship and made his way to the Protectors' camp. There, he came upon the grim discovery that another Mandalorian faction had murdered his comrades and set fire to numerous structures. Chopper was able to free Sabine and Ezra. Together, they located Fenn, who was in a state of despair over the loss of his people. Following a brief exchange between Fenn and Sabine, Chopper detected a signal.
The rebels were then attacked by an Imperial probe droid, but Sabine successfully destroyed it. Before they could depart on the Phantom II, a contingent of Imperial super commandos, led by Gar Saxon, arrived. The rebels scattered throughout the complex, but Saxon and his forces managed to capture both Chopper and Ezra. Sabine and Fenn managed to evade capture and found a secure vantage point from which to observe the enemy.
In the meantime, Gar Saxon subjected Ezra and Chopper to interrogation. Ezra attempted to pass himself off as a scavenger, but Saxon was unconvinced and coerced him into cooperation by threatening Chopper. Despite Ezra's attempts to mislead Saxon, the Viceroy managed to extract information revealing that Fenn Rau had dispatched him. Elsewhere, Sabine and Fenn debated the advantages of rescuing Ezra and Chopper. Sabine was resolute in her determination to rescue her friends and successfully persuaded Fenn to retrieve the Phantom II to prevent it from falling into Imperial hands. Sabine was concerned that the Empire would discover the location of the Phoenix rebel base. Due to his animosity towards Saxon, Fenn agreed to a temporary alliance with Sabine.
Back in the hut, Saxon realized that Ezra was a Jedi after he managed to deflect Saxon's blaster fire away from Chopper. Sabine successfully rescued her companions by using smoke grenades to disorient Saxon and his guards. The rebels then attempted to escape aboard the Phoenix II only to discover that Fenn had absconded with the ship. Saxon and his super commandos then surrounded the rebels and confronted Sabine. Showing respect for Sabine's mother, he offered to spare Sabine's life if she assisted them in locating Fenn and pledged her allegiance to Saxon. Sabine refused and instructed Chopper to activate Frequency 337 on her helmet, which temporarily disoriented Saxon and his men.
Chopper activated his rocket boosters, while Sabine and Ezra shared a jetpack. The three rebels fled into a canyon but were pursued by Saxon's Mandalorian super commandos. Ezra managed to use his lightsaber to damage the jetpack of one of their pursuers, causing him to drop out of the chase. Sabine then deployed several grenades to obstruct the path of the super commandos. Saxon and his remaining forces caught up with the rebels. At one point, Ezra was compelled to ride on Chopper. Meanwhile, Sabine managed to shoot down another Mandalorian super commando and detonate his jetpack.
After a treacherous pursuit, the rebels arrived at Gar Saxon's starship, which was situated at the top of the plateau. The rebels devised a plan to steal it and escape off-world. However, Saxon and his remaining super commando caught up with them and managed to disarm Sabine. Just before they could execute the rebels, Rau had a change of heart and returned in the Phantom II. Fenn managed to shoot the remaining super commando and destroy Fenn's ship. This enabled Ezra and Chopper to escape aboard. Following a struggle, Sabine managed to fend off Saxon and escape aboard the Phantom II.
As a consequence of the second mission to Concord Dawn, the rebellion learned that the Protectors of Concord Dawn had been killed by Imperial super commandos under the command of Viceroy Saxon. Sabine's actions to save Ezra and Chopper, despite their non-Mandalorian status, earned her the respect of her former adversary Fenn Rau. With his followers dead and Saxon vowing to kill him, Rau chose to join the rebellion. This resulted in the rebels gaining the support of an experienced Mandalorian warrior and commander.