Nine-Tailed Demon Fox's Attack

The Nine-Tails attacked the shinobi village of Konohagakure on the night of October 10, twelve years before the start of the series. After causing untold death and destruction, the Nine-Tails was stopped by the village's leader, the Fourth Hokage, who gave his life to seal the Nine-Tails into the newborn Naruto Uzumaki.

Prelude
The recently-appointed Hokage, Minato Namikaze, was married to Kushina Uzumaki, the jinchūriki of the Nine-Tails. When Kushina became pregnant and the birth of their son drew near, special precautions had to be taken due to the fact that the seal keeping the Nine-Tails within her would weaken during childbirth, thus carrying the risk it might escape. News of Kushina's pregnancy was kept a secret from the general population and the delivery itself would take place in a remote cave away from the village. Minato's predecessor, Hiruzen Sarutobi, organized security: the site would be protected by a barrier, several Anbu would guard the area, and another Anbu (Taji) and Hiruzen's wife (Biwako) would be midwives. Minato, meanwhile, would monitor the seal, keeping it stable during the delivery and restoring it to its original strength as soon as their son was born.

Despite all the secrecy, news of Kushina's pregnancy was discovered by Tobi, who overheard it from Kakashi Hatake, Minato's student, while he spoke to Rin Nohara's grave at the Konoha Cemetery. Tobi located where the birth was taking place, infiltrated the barrier, killed the Anbu stationed outside, and arrived inside the cave mere moments after the child, Naruto, was born. Tobi killed the midwives and took Naruto hostage, threatening to kill him if Minato attempted to restore the Nine-Tails' seal. Minato was able to take Naruto back, only to discover explosive tags planted on him. Minato was forced to teleport away with the Flying Thunder God Technique to keep Naruto safe, leaving Kushina behind with Tobi.

Tobi moved Kushina to a new location and placed her under restraint while he took steps to further weaken the seal. As the seal was about to break, he used his Sharingan to enter Kushina's subconscious and place the Nine-Tails under his control. The Nine-Tails was extracted, a process that Kushina survived due to her Uzumaki heritage. Tobi attempted to have the Nine-Tails kill her, but Minato tracked them down in time to save her and escape to a safe-house where he left Naruto. Unconcerned by them, Tobi led the Nine-Tails back to the village.

Attack
Even before the Nine-Tails arrived in the village, some sensed its approach: the young Itachi Uchiha felt something ominous and his infant brother, Sasuke, began to cry; Kakashi detected a change in the air as he spoke with Might Guy, though he did not know the cause; Hiruzen sensed the Nine-Tails while he worked in his office, aghast by the implication. Tobi snuck back in to the village and summoned the Nine-Tails to his location, using it to launch an immediate attack. An Anbu reported the Nine-Tails' appearance to Hiruzen, who had already changed into his combat uniform to lead the village's defense.

Minato teleported to the Hokage Rock to lend his assistance. The Nine-Tails immediately noticed his presence and attacked with a Tailed Beast Ball, which he sent away with his Flying Thunder God: Guiding Thunder, a contribution noticed by the Ino–Shika–Chō as they headed into battle. Minato attempted to locate Hiruzen so that he could tell him what happened, but he was stopped by Tobi. Tobi started to teleport Minato away, but Minato used his own teleportation to escape. Tobi followed. From Tobi's actions, Minato speculated that Tobi was in fact Madara Uchiha, who had decades earlier tried to use the Nine-Tails to destroy Konoha. Tobi didn't deny Minato's claim, but he did allude to having some purpose behind the attack. Minato and Tobi clashed, with Minato, after some difficulty, finally managing to strike Tobi with the Rasengan.

During his attack, Minato was able to brand Tobi with the Flying Thunder God formula, allowing him to teleport to Tobi's location whenever he wanted. He immediately did do to strike again, this time to place a Contract Seal on Tobi that removed the Nine-Tails from his control. Injured and deprived of his best weapon, Tobi fled, vowing that it was only a temporary setback. In Konoha, meanwhile, many of the village's children had been taken away from the village and confined behind a barrier so that they would not be killed trying to protect the village. Others weren't so fortunate: Iruka Umino's parents, Kohari and Ikkaku, died protecting him from the Nine-Tails' attacks; in the anime, Itachi ran through the village with Sasuke in his arms, trying to find their own parents.

Once free from Tobi's control, the Nine-Tails tried to retreat from the village. It was pursued by Konoha's forces, led by Hiruzen, prompting it to retaliate with another Tailed Beast Ball. Minato returned to the village in time to stop it by summoning Gamabunta above it, having Gamabunta keep the Nine-Tails restrained while he gathered the chakra to teleport it away. Minato took the Nine-Tails to the safe-house where he'd left Kushina and Naruto, it being the furthest away from the village that he could get. Kushina retrained it and cut off access to the area with her Adamantine Sealing Chains while she and Minato decided what to do with it.

Already dying from her earlier ordeal, Kushina offered to have the Nine-Tails sealed back in her once again so that it would die with her. Believing the Nine-Tails' power would be needed in the future to face Tobi, Minato rejected this idea, deciding instead to seal the Nine-Tails into Naruto using the Eight Trigrams Seal. Because the Nine-Tails was too powerful to contain within the body of an infant, Minato used the Dead Demon Consuming Seal to cut its chakra in half, leaving only its yang chakra. When it realized what they were planning, the Nine-Tails tried to kill Naruto, forcing Minato and Kushina to use their own bodies to shield him. While Kushina had some final words with Naruto, Minato gave the key to the seal he was about to use to Gerotora and then sent him to Jiraiya.

Hiruzen followed Minato to their location, but could not break through Kushina's barrier. Minato didn't have the time necessary to tell Hiruzen what had happened, choosing instead to make a request of Konoha's villagers via Hiruzen: to regard Naruto as a hero for helping save the village and not hate him for containing the monster that had killed so many. With that, Minato sealed the Nine-Tails into Naruto, adding his and Kushina's chakra to the seal so that they could watch him grow up and someday help him gain control of the Nine-Tails.

Aftermath
Hiruzen brought Naruto back to Konoha. With Minato and Kushina dead, Hiruzen decided it would be best if nobody knew of Naruto's relation to Minato so that Minato's old enemies wouldn't come after him; to that end, he gave Naruto Kushina's family name. Hokage once again, Hiruzen shared Minato's final request with the survivors. Although some, predominately those who personally knew Minato, were willing to follow his instructions, most were not, since they were incapable of setting aside their grief and bitterness in the awake of the death and destruction of the attack. Hoping that future generations wouldn't hate Naruto in the same way that their parents did, Hiruzen forbade anyone from discussing the Nine-Tails. This largely failed, as those in Naruto's age group only copied their parents' hate, though they didn't understand why. Naruto, already an orphan, grew up lonely.

Because Minato was never able to explain what had happened, Konoha's villagers were left to come up with their own explanations for the Nine-Tails' attack. The Nine-Tails had historically attacked human settlements, drawn to large concentrations of humanity's dark nature. Accordingly, many assumed it was just a natural occurrence that nobody was responsible for. Konoha's leadership, however, believed an Uchiha was responsible, both because of the Sharingan's famed ability to control the Nine-Tails and the Uchiha's absence while defending the village. (In the anime, the Uchiha avoided direct engagement with the Nine-Tails on the orders of Danzō Shimura.) The Uchiha, having helped create Konoha decades earlier, were offended by this mistrust, setting in motion the events that would lead to the Uchiha Clan Downfall.

Jiraiya, as Minato's former teacher, believed there was more to the events of that night. He, like Minato, suspected Madara Uchiha's involvement, despite how old Madara would have had to be at the time. He also felt that Minato's decision to seal the Nine-Tails into his own son was significant, assuming he intended for Naruto to someday gain control of the Nine-Tails' power for some purpose Jiraiya couldn't guess. As such, Jiraiya took on Naruto as a disciple once he was old enough, training him to take advantage of the Nine-Tails' chakra and using the key Minato sent to him to accelerate the process. Tobi, the threat that Minato wanted Naruto to be prepared for, would ever-after deny any involvement in the attack, insisting it was the natural outcome of Konoha's years of benefiting off the misfortunes of others.

In the anime, the Nine-Tails left behind some residual chakra during its attack. Kazuma collected this chakra and sealed it within his own son, Sora, turning him into a pseudo-jinchūriki.