Nine-Tailed Demon Fox's Attack

Twelve years before the start of the series, after the end of the Third Great Shinobi World War, the Nine-Tailed Demon Fox attacked the village of Konohagakure.

The attack coincided with Kushina Uzumaki, the second jinchūriki of the Nine-Tails, giving birth to Naruto. It was mentioned that the jinchūriki's seal was at its weakest when giving birth, thus, it was carried out in secret, with Biwako Sarutobi, the Third Hokage's wife, as her midwife, a few ANBU as security, and with Minato keeping the Four Symbols Seal holding the Nine-Tails secure. The location was eventually tracked by a man in a mask, who resembles Madara Uchiha, killing the ANBU and Biwako, and holding the newborn Naruto hostage, ordering Minato to walk away from Kushina. Presumptively, it was at this moment that he released the Nine-Tails to wreak havoc in Konoha.

Nobody was able to stop the Nine-Tails until Minato Namikaze, the Fourth Hokage, arrived to apply the seal on the Nine-Tails and sealed the Yang portion of the Nine-Tails' chakra into his newborn son, Naruto Uzumaki while keeping the Yin portion within the Death God. Kushina somehow suvived the unsealing process because of her clan's longveity, however was severely weaked. The village suffered heavy casualties during the attack, such that few of the villagers would forgive Naruto (who they viewed as the fox) for its actions despite the fact that he was the one who contained the beast.

Though the Nine-Tails had attacked many settlements regularly throughout history for no apparent reason, Jiraiya, Minato Namikaze, and Itachi Uchiha speculate that Madara Uchiha was behind the attack on Konoha. Madara denies this and attributes its rampage as a natural occurence: however, Minato claims to have fought him on the night of the attack.

As the Uchiha clan's Sharingan is able control the Nine-Tails, the elders of the village suspected them of being responsible of unleashing the attack. It was this spite that led them to attempt a rebellion, which ended with their mass assassination before it could happen.

In the anime, the Nine-Tails is revealed to have left behind large amounts of its chakra during the attack that, when gathered by Kazuma, allowing him to turn Sora into a pseudo-jinchūriki.

The Ninetails was so powerful that, even at a young age, Itachi was able to sense the power of the Ninetails