Uchiha Clan Downfall

The, also called the , was the massacre of the Uchiha clan by Itachi Uchiha.

Background
Following the Nine-Tails' attack on Konoha orchestrated by Tobi, Konoha's leadership began to suspect that an Uchiha was behind the attack as the Sharingan possessed the ability to control the Nine-Tailed Demon Fox and begun to look at them with suspicion from that point onwards.

According to Obito, the Uchiha were felt as thought they had grown distant from the rest of the village. This ultimately rekindled the clan's feelings of hatred towards the Senju-influenced government, and the belief that they deserved more power than what they had as the heads of the police force, which manifested in the paranoid belief that the position had been offered to them to "keep them away" from the position of leadership that they felt they were entitled to. In planning the coup d'état, they entrusted Itachi Uchiha who was an Anbu, to be their spy. However, a pacifist by nature, Itachi knew that if the Uchia betrayed the village, they would cause another Shinobi World War and instead provided Konoha with information on the Uchiha's plans. . The Third Hokage tried to negotiate a peaceful soultion, but, as time passed and that approach seemed to get them nowere, even Shishui was forced to admit to Itachi that "It doesn't look like we can stop the Uchia coupt d'etat".

The Uchiha clan, however, was not completely ignorant of Itachi's double-agent status and began to suspect him due to his strange behaviour since joining the Anbu, and asked his close friend Shisui Uchiha to keep an eye on him. However, Shisui was also against the coup d'etat like Itachi, but could see that it could not be stopped through diplomatic means, and couldn't envision any other way to avert it but to try to mentally enslave them with his Mangekyō Sharingan's strongest technique. However, Danzō Shimura did not trust him, and, unwilling to bet the village's future on such a risky plan, stole his right eye, bent on protecting the village in his own way. Shisui then entrusts it to Itachi, asking him to stop the rebellion. Soon after, covering up the nature of Shisui's death as a suicide, Itachi is accused of murder and loses the trust of several of its members. Itachi allowed them to believe that as he became more distant from his kin. Even Fugaku, the clan's leader, and Itachi's father who defended his son of being accused, seemingly washed his hands of Itachi, unable to understand his son anymore.

Though the Third Hokage Hiruzen Sarutobi, was aware of the threat posed by the Uchiha,[1][2] he was unwilling to confront them, as they had fought together in the last war, but, as Shishui had remarked -telling Itachi "It doesn't look like we can stop the Uchia coupt d'etat"-, the Uchia were unwilling to consider a diplomatic solution, a position shared by Homura, Koharu and Danzō Shimura. Despite that, as the latter admitted, when push came to shove the Hokage would have been willing to protect Konoha. This would have meant that, since the Coup d'etat was unavoidable, the Uchia being unwilling, as Shishui remarked, to match the Third Hokage's attempts to resolve the conflict diplomatically, the clan was destined to destruction. An outright confrontation would have let the betrayal out in the open, putting Sasuke on the opposite side of the village and therefore endangering his life. Contrary to Tobi/Obito's original assertion, it wasn't Itachi that decided to barter with the Council to spare Sasuke's life, after having been unable to kill him, but rather, Danzo himself offered Itachi the chance to save his brother's life, saving the village and by extension, the world from a war on a global scale[3], on the basis that they shared the same feeling for the village and, apparently, he seemed to trust him in a way he didn't trust Shishui.

According to Tobi's recounting to Sasuke, Itachi met with Tobi, whom he believed to be Madara Uchiha. As Madara was ostracised by the clan for causing unrest during the first days of Konoha's formation, Tobi claims that Itachi allowed him to aid in the slaughter in return to leave the rest of Konoha and Sasuke be.

Attack
On the night of the slaughter, with Tobi's help, Itachi proceeds to murder every member of the Uchiha clan until only his parents remain. Hesitating before killing them, Itachi learns his parents loved and respected him despite his choice to side with the village over his clan and that their final wish, was for Itachi to take care of Sasuke.

When Sasuke returned that night late from his own training, he finds his kin's corpses littering the streets, and Itachi standing over their parents' bodies and demands to know what he has done. Intending to have Sasuke kill him as punishment for his crime, Itachi used Tsukuyomi on Sasuke to make him think that he alone murdered their clan in cold blood. Claiming to have spared him as he was not worth killing, Itachi convinces Sasuke to live a life of vengeance. Sasuke activated his Sharingan for the first time and chased after Itachi, managing to knock off his forehead protector. Itachi, weeping as he picked it up, left Sasuke unconscious and departed from the village. Sasuke was greatly traumatised by the experience, and did not remember awakening his Sharingan.

Aftermath
Following the event, only three members of the Uchiha clan remained alive: Obito Uchiha, Itachi Uchiha, and Sasuke Uchiha. Later on, Itachi and Obito would pass on. Madara Uchiha was also resurrected later on, but eventually died again. Eventually, Sakura Haruno would marry into the clan by Sasuke and give birth to Sarada Uchiha — thus beginning the process of reforming the clan.

Before leaving Konoha, Itachi asked Hiruzen to protect Sasuke from Danzō and the other two elders Koharu and Homura, and to never disclose the truth of the events surrounding the massacre. He also made it a point to threaten Danzō as well with the threat of leaking information on Konoha to enemy villages, should he ever lay a hand on Sasuke. Soon after leaving, Itachi joined the Akatsuki to keep Konoha safe from the organisation until the day that Sasuke would come looking for him. Aside from Itachi and Konoha's elders knowing the truth, the official story the latter made up was that Itachi turned rogue due to losing faith in the clan.

The attack had a immense psychological effect on Sasuke, who woke up in the hospital with no memories after Itachi's speech and unable to utilise the Sharingan until five years later after becoming a member of Team 7. However, despite feeling that there was more to the event than what he knew, it only motivated him to strive to gather enough power to kill Itachi, ultimately leading him to Orochimaru whose guidance enabled Sasuke to obtain the means. However, after Itachi's death, Sasuke learns the truth of the massacre from Tobi. Crushed by this revelation, despite the fact that the Uchiha clan's actions would have destroyed the village, themselves and many others beyond village borders, and driven by his clan's hatred, Sasuke resolved to destroy Konoha to avenge the tragic lives both he and Itachi led, and to purify the clan's name by severing his ties with the village and the "corrupted shinobi world" that shunned it. The drive is furthered when Danzō admits his role in the massacre yet claimed to have no reason to hide it any longer if Sasuke found out the truth.

Tobi later revealed the truth of the Uchiha Massacre to Naruto Uzumaki, Kakashi Hatake, and Yamato. However, with no evidence behind Tobi's words, Kakashi suggested to Naruto and Yamato to keep the information to themselves so as not to hinder Konoha while being rebuilt after Pain's invasion. A reincarnated Itachi, upon learning that Naruto had also come to know the truth, asked him not to reveal the truth so that the Uchiha clan name can maintain its honour. Later on, Kabuto Yakushi, being an experienced deep-cover agent, revealed that he too knew the truth behind the incident.