|"Earth King Kuei, look at who you're fighting! Fire Nation, yes, but also Earth Kingdom, Water Tribe, and now, Air Nomad."|
|— Aang to Earth King Kuei.|
After the newly crowned Fire Lord Zuko withdrew his support for the Harmony Restoration Movement, Avatar Aang and Katara met up with Earth King Kuei to discuss the current situation in Yu Dao. The Earth King, wanting to stand up for himself instead of being weak as he had been before, declared that he was going to organize his troops to "enforce harmony" in Yu Dao. Aang pleaded him not to take such drastic action, but Kuei responded that by not agreeing with him, Aang now was against him.
Meanwhile, at the Fire Nation Royal Palace, Zuko was informed about the Earth King's planned invasion of Yu Dao. In order to protect the people of his nation, the Fire Lord responded by readying his fleet to fight Kuei's army for the sake of preventing the Fire Nation citizens from being forced to leave the colony.
At the Beifong Metalbending Academy, Suki, riding a war balloon, stopped to gather Toph and Sokka and alerted them about the Fire Nation and Earth Kingdom armies headed toward Yu Dao. Toph and Sokka agreed to help try to stop Zuko's army from reaching the colony, and the three set off to find the approaching Fire Nation Army.
At this time, because Aang failed to secure a deal to remove the Fire Nation, Smellerbee ordered her mob to attack Yu Dao, and they broke through the walls of the colony. She and Longshot discovered upon walking into the colony that Sneers had been in a relationship with Kori Morishita, angering Smellerbee. Sneers explained that Yu Dao was a part of both the Earth Kingdom or Fire Nation, but before things could be settled completely, a protester began attacking them. The Yu Dao Resistance, led by Kori, and Smellerbee's mob started to fight, but before long, the Earth Kingdom Army arrived.
Meanwhile, Toph, Sokka, and Suki sneaked underground below the invading Fire Nation Army. From below, Toph metalbent her way into one of the tundra tanks, and the three secured control over it. Sokka subsequently came up with an idea to disable all of the tundra tanks and asked Suki to pull them up to be next to as many tanks as possible.
Back at the colony, the Official Avatar Aang Fan Club from Yu Dao arrived to assist Aang, but he rejected their support. General How read a decree stating that the colony of Yu Dao was to be reclaimed by the Earth Kingdom. The Fire Nation Army arrived after the decree was read, and How implored for Aang to end the battle by killing Zuko. However, Aang did not want to take such action and tried to reason with How. Sokka and Toph appeared from one of the nearby tanks, and upon Sokka's command, Toph metalbent all the screws from the tundra tanks around them, essentially disabling them. This caused the two armies to start fighting on foot, prompting Aang to enter the Avatar State to stop the violence. Katara snaps him out of it, bringing him away from the battle. Here, Katara confessed to Aang that when she saw the Morishita family, she also saw their future as a multicultural family and asked him to find somewhere where he can have the clarity of mind to make the right decision.
In the battle area, the members of the Official Avatar Aang Fan Club prevented the armies from killing each other. Upon viewing this, Katara came up with a plan to do the same: Sokka and Toph would disarm Fire Nation troops while she worked on the Earth Kingdom troops. After they agreed to do so, all of them descended onto the battlefield. Suki and Toph were quickly outnumbered by the amount of Fire Nation soldiers attacking them, but just when it seemed that they were going to be taken down, Ho Tun, Penga, and The Dark One suddenly appeared, defeating all of the soldiers by metalbending their helmets.
Katara began to attack Earth Kingdom troops with waterbending, but when she saw the Earth King's war balloon floating overhead, she quickly waterbent an ice spiral to propel herself into the balloon. She arrived to see Kuei sitting alone inside, saying that he wanted to prove that he was brave enough to fight on the battlefield with his troops. After a bit of conversation, Katara convinced him to come down from his war balloon in order to meet the people his decisions affected.
As the fighting below escalated, a beam of light suddenly broke out in the distance. Aang had entered the Avatar State, and he fled down toward the colony. In a massive display of earthbending, he divided the colony from the battlefield. However, in the process, Fire Lord Zuko fell into the chasm and began plummeting to his death, but Aang grabbed his hand, saving him from doom. As Aang exited the Avatar State, Katara and the Earth King arrived. Aang began explaining to Kuei that he was not just fighting the Fire Nation, but the other nations as well, including Aang's, going on to say that he was battling a whole new type of world and the colonies did not need to be separated. Kuei realized that his actions were wrong, and conversely, Zuko realized that his own actions were justified, causing him to collapse and the battle to end.
Four days later, Aang confronted Roku's spirit and explained that there was nothing more he could learn from him now that the world had changed so much. In tears, Aang tore off the firebending emblem from his meditation beads, causing Roku's apparition to vanish.
When Zuko woke up, the Fire Lord realized that he had to make decisions for himself and apologized for having put pressure on Aang by having forced him to promise to take Zuko's life if he went down the wrong path. In order to be better at peace, Zuko outed his desire to connect with his mother's side of the family, a journey which would eventually lead him to find her at Hira'a.
With the peace between the Earth Kingdom and the Fire Nation restored, a meeting between the respective leaders was later arranged under supervision of the Avatar. They agreed upon a coalition government, with two representatives each from the Earth Kingdom and Fire Nation. Many colonies followed suit, ultimately leading to the creation of the United Republic of Nations.
Aang held a meeting with members of both the Yu Dao and Ba Sing Se chapters of the Official Avatar Aang Fan Club. He explained that he wanted them to continue the culture of his people and dubbed them the first Air Acolytes.
- DiMartino, Michael Dante; Konietzko, Bryan; Yang, Gene Luen (writer), Sasaki of Gurihiru (penciling, inking), Kawano of Gurihiru (colorist), Heisler, Michael; Comicraft (letterer). The Promise Part Three (September 26, 2012), Dark Horse Comics.
- DiMartino, Michael Dante; Konietzko, Bryan; Yang, Gene Luen (writer), Sasaki of Gurihiru (penciling, inking), Kawano of Gurihiru (colorist), Heisler, Michael; Comicraft (letterer). The Promise Part Two (May 30, 2012), Dark Horse Comics.
- DiMartino, Michael Dante; Konietzko, Bryan; Yang, Gene Luen (writer), Sasaki of Gurihiru (penciling, inking), Kawano of Gurihiru (colorist), Heisler, Michael; Comicraft (letterer). The Search Part Three (October 30, 2013), Dark Horse Comics.