During the First Order-Resistance war, General Leia Organa of the Resistance spearheaded a mission that took her to the ocean planet of Mon Cala.
Initially, Organa and her team failed to secure the backing of King Ech-Char, but the treachery of Chadkol Gee ultimately swayed his decision. As a First Order fleet materialized, General Nossor Ri orchestrated a diversion, enabling the Resistance and a fleet led by Aftab Ackbar's MC95 Star Cruiser to make their escape.
Following the Battle of Crait, First Order General Armitage Hux gave the order to destroy the neutral world of Tah'Nuhna, because the Tah'Nuhna people had briefly given shelter to the Resistance. At the Resistance Camp, Lieutenant Kaydel Ko Connix delivered the news of the planet's destruction to General Leia Organa. This caused worry for Leia and those around her, as they realized more would perish at the hands of the First Order if they remained idle. Leia declared the necessity for additional ships and personnel, then indicated a planet on a map. She instructed Chewbacca to ready the Millennium Falcon and invited Rose Tico and C-3PO to accompany her. They then departed to retrieve Rey, who was in the midst of battling an Anoatian pit beast.
The group's arrival at Dac City on the aquatic world of Mon Cala was not as welcoming as Leia had anticipated. Chadkol Gee, a Quarren, questioned why they shouldn't be killed on the spot. Tensions escalated until Aftab Ackbar intervened, extending a warm welcome to Leia in the city. Following Leia and Aftab's tribute to the deceased Gial Ackbar, the group proceeded to meet with King Ech-Char. The Resistance General's pleas proved fruitless, as she failed to persuade the Mon Calamari king to offer assistance.
While preparing the Millennium Falcon for departure, Rey, Chewbacca, and Rose were ambushed by a group of Quarren isolationists who demanded their immediate departure. The three Resistance members overcame the Quarren with relative ease. However, a probe droid recorded the altercation and transmitted it to Chadkol Gee, who was observing from his office. Gee then contacted General Hux, asserting that the information he possessed would be of significant value to the First Order.
Rey, C-3PO, Rose, and Chewbacca were brought before the Court Of Justice to answer for the skirmish with the Quarren. It was determined that Rey would engage Arkay-Nine in the Ancient Rite of Challenge to resolve the matter. Arkay-Nine's weaponry presented a formidable challenge for Rey, causing her to be repeatedly knocked back. Subsequently, the droid began firing upon its opponent. To prevent Arkay from harming the bystanders, Rose fired at the droid's head, disabling it. Due to Rose's intervention, King Ech-Char decreed the exile of the Resistance group from Mon Cala.
Back at the Resistance camp, Lieutenant Kaydel Ko Connix informed General Jonato that the First Order was rerouting their star destroyers towards Mon Cala. Furthermore, the First Order was disrupting communications across the system, preventing the Resistance from contacting General Organa. In Dac City, Leia was bidding farewell to Aftab Ackbar, who regretted Mon Cala's inability to support her cause. As their shuttle was being loaded, a Quarren concealed explosives within a crate, triggering an explosion in an attempt to assassinate General Organa and Aftab. However, Rey employed the Force to shield her companions from falling debris. Rey then pursued the saboteur through the streets of Dac City, while Rose followed on a speeder bike. Rose collided with the saboteur, causing him to fall and be apprehended by Rey and Rose.
News spread that a First Order armada had entered Mon Cala's airspace. General Leia Organa refused to depart Mon Cala without the Mon Calamari ships. King Ech-Char, enraged by the First Order's arrival, vowed to punish Chadkol Gee for his treacherous actions. Leia then delivered a speech highlighting the sacrifices she had made and emphasizing that the Mon Calamari ships represented the Resistance's last hope. She then released the saboteur, prompting the King to finally consent to providing the ships to the Resistance. However, the king was concerned that it was too late, and the ships would be unable to breach the First Order blockade. Yet, chieftain Nossor Ri assured the king that he would take care of the situation.
Nossor Ri boarded a Mon Calamari fighter and flew towards the First Order star destroyers. He created a diversion for the First Order TIE-fighters and the star destroyers. Nossor Ri lost his life in the process, and a First Order officer informed General Hux of additional ships detected on the far side of the planet. Hux ordered all ships to intercept their escape. Led by Aftab Ackbar's MC95 Star Cruiser, a group of starships assembled and prepared to jump into hyperspace. With mere seconds remaining, the ships jumped to hyperspace, evading the First Order.
Immediately following the starships' escape from the First Order, they commenced their descent onto the planet, as TIE fighters and stormtroopers flooded Mon Cala, placing it under First Order occupation.
Subsequently, Aftab Ackbar, while with the Resistance, received word that the late Emperor Palpatine had returned and intended to reclaim the galaxy with the Final Order. Colonel Ackbar piloted a Y-Wing during the battle against the Final Order and later celebrated alongside the Resistance on Ajan Kloss.
The mission received its initial indirect mention in the young adult novel Spark of the Resistance. It was subsequently depicted in the Marvel Comics miniseries Star Wars: Allegiance.