- "With Roku gone, and the great comet returning, the timing was perfect to change the world. Fire Lord Sozin knew the next Avatar would be born an Air Nomad, so he, with the First Hokage's help, wiped out the air temples. Unknown to the Fire Lord, the First Hokage kept the surviving Air Nomad lineage hidden in Konoha. Sozin wasted the remainder of his life searching in vain, as the Second Great Shinobi War waged on. The greatest hope of the shinobi world."
- ―- Third Hokage Hiruzen Sarutobi narrating the memoirs of the genocide
The Air Nomad Genocide was an enormous massacre carried out by the Land of Fire and Konohagakure against the Air Nomad clan, nearly resulting in the extinction of the entire clan, as well as the fauna that lived in their air temples. Among the very few survivors of the massacre were the family of Kushina Uzumaki, mother of the future Avatar Naruto Uzumaki, which were ironically the prime target. The outrage over this destruction of an entire culture led the other four of the five great nations to declare war against the Land of Fire, leading to the First Great Shinobi War.
After Lord Sozin left Avatar Roku to die by inhaling the toxic fumes during the volcanic eruption of his island shortly after the end of the Warring States Period, Sozin started his plans to "spread the Land of Fire's peace and wealth to the rest of the world", and transforming the five great nations into a single nation that would ensure peace and prosperity for the generations to come.
Sozin knew that, as per the Avatar Cycle, Roku's successor would be reborn as an Air Nomad. Recruiting the help of an unwilling First Hokage Hashirama Senju and Konohagakure's co-founder Madara Uchiha, Sozin planned an initial surprise attack against the Air Nomad clan. This attack was strategically planned to occur during the arrival of the Great Comet, later renamed "Sozin's Comet", where the firebending of the Uchiha Clan and the Land of Fire Royal Family would grant them more power than usual.
With the threat of an oncoming war, the Air Nomads' Council of Elders, believing Mito Uzumaki to be the Avatar, told her of her supposed identity at the age of twelve, when under normal circumstances their identity is told to them at age sixteen. Nevertheless, Gyatso believed that Mito should have a normal childhood, and continued to engage with her in fun and games. Contrary to Gyatso, Pasang and the rest of the Council of Elders agreed to seal the spirit of the Nine-Tails within Mito to protect the Air Nomads from the Land of Fire and Konohagakure, sending her to the Eastern Air Temple so she could complete her airbending training. After the sealing procedure was over, Mito overheard the Council's plan to her, and, unable to deal with the burden she carried, abandoned the temple with a female flying bison and her calves. This inadvertently saved her from Sozin's imminent assault against the Air Nomads.
Despite their pacifistic culture, the Air Nomads violently fought back against their attackers, with varying degrees of success. Ultimately, however, they were no match for the sheer number and firepower of Konoha's shinobi.
A small number of Air Nomads managed to escape the initial attack on the temples, and were able to hide from Konoha and the Land of Fire's military. Some of these included the ancestors to Suchin's family, who later became the mother of Karin as well as the family of Tenzin, who founded the Air Acolytes in order to preserve Air Nomad culture.
Fire Lord Sozin changed his tactics, removing relics from the temples and building small settlements in the mountains furnished with these relics in order to give the appearance they were inhabited by Air Nomad refugees. Using Konoha spies to spread lies and rumors about these safe houses across the five great nations, Sozin was able to lure and kill most of the Nomads who managed to escape the genocide.
One of the only known Air Nomads who managed to survive was the one the Land of Fire and Konoha sought to eradicate, Mito, progenitor of the next Avatar, Naruto Uzumaki. By running away from the temple, she managed to save herself and fall under the hands of the First Hokage Hashirama, who, as an avid believer of the Avatar, broke protocol and loyalty to his own nation, and his Mito's identity from Sozin by helping her to hide within his hidden village of Konoha.
Sozin spent the next twenty years of his life in search of whom he believed to be the Avatar, unaware that his most trusted military leader was hiding her the whole time. Sozin eventually died at the age of 102 without ever finding Mito, leaving a legacy of war and death to the world. Mito eventually became the mother to Kushina Uzumaki, whom she believed to be the Avatar. After discovering she was not, Mito was relieved to know her daughter avoided what she saw as a cursed fate, but upon her death, the Nine-Tails had to be sealed within Kushina herself. Afterwards, Kushina married Minato Namikaze, the Fourth Hokage, whom she had a son with, Naruto. Naruto would become both the Avatar and the Jinchuriki of the Nine-Tails, being the first Avatar in history to possess both the spirit of Raava and a tailed beast within him.
The Air Nomad Genocide was followed by a propaganda boost from the Land of Fire. By 114 AG, children in Konoha were taught that Sozin and Hashirama battled "Land of Air Army", mixing the Air Nomads with the Land of Wind at large and omitting the facts that not only the Air Nomads were a peaceful clan, but that the Land of Air only fought back after the genocide. This event made the Land of Air uneasy and disgruntled with the Land of Fire for the next centuries; Sunagakure shinobi despised Konohagakure shinobi for the massacre, and both remained vocal enemies during both the Second and Third Great Shinobi Wars until peace was restored after the Konoha Crush in 115 AG. While Fire Lord Azulon and the Third Hokage Hiruzen Sarutobi attempted to correct the mistakes of their past leaders, the warped sense of reality was already massively prevalent in society, and figures such as Ozai, Azulon's own son, still cherished these events. The nations mostly lost knowledge over the Air Nomads, leading them and the flying bison to be considered ancient myths and legends akin to the Sage of Six Paths. Intellectuals and elders were the ones who generally knew about the Air Nomads, but to them it was an ancient clan and a dead culture.
One hundred and fourteen years after the genocide, Naruto learned of the fate of the Air Nomads after discovering he was the Avatar. After Ozai took over the Land of Fire, Naruto revisited his grandmother's former home at the Southern Air Temple, where he discovered countless of shinobi and monk corpses next to the skeleton of Gyatso. The images of what remained of the genocide came to forever plague Naruto.
Hoping to restore the culture and traditions of the Air Nomad clan, Tenzin founded the Air Acolytes in 90 AG at the Fire Temple. An international group of monks and nuns, the Acolytes carried over the few cultural records of the Air Nomads through practice, despite all of them but Tenzin being nonbenders themselves.
However, not all air temples were abandoned after the shinobi wars; the Northern Air Temple was rediscovered by Land of Earth refugees in 101 AG. Because they were forced from their homes duo to a flood years earlier, they stumbled upon the abandoned structure and made it their new home. The Mechanist, their leader, used his technological prowess to modify segments of the temple and create a safe haven for his people. When Team Kakashi arrived at the Northern Air Temple during their journey to save Konoha, Naruto became angry over the temple's new inhabitants for "vandalizing" the home of his clan. He relented, however, after he witnessed Teo, a mere nonbender, demonstrating the "shinobi spirit" and how he fought to keep his people together even in the face of adversity after they fended off Ozai's loyalists.