Third Shinobi World War

The has been rarely shown in the series outside the Kakashi Gaiden arc. It is suggested that it began with the disappearance of the Third Kazekage. Sunagakure went to such lengths to find its Kazekage that it provoked intervention from neighboring countries. Konohagakure and Iwagakure eventually began fighting across Kusagakure. It was not until the destruction of the Kannabi Bridge that the war began turning in Konoha's favor.

Minato Namikaze became a hero during the war and received his nickname, "Konoha's Yellow Flash". Kakashi Hatake, having gained his Sharingan from Obito Uchiha during the mission to destroy the Kannabi Bridge, also gained fame as "Copy Ninja Kakashi". Itachi Uchiha was traumatized by the violence of the war and grew to crave peace at any cost because of it. The rest of his life would be greatly affected by this experience.

In Amegakure, Yahiko, Nagato, Konan, and many other shinobi formed a group that fought the rule of Hanzō. Hanzō called in the assistance of Danzō and his Root ANBU, but failed to suppress the group. The confrontation between the two sides did lead to a slaughter of all Amegakure and Root shinobi present, except for Hanzō, and to the death of Yahiko. In the anime, Hiruzen Sarutobi made a peace treaty with the Tsuchigumo clan sometime during the war.

Trivia

 * It was claimed in Naruto Shippūden 3: Inheritors of the Will of Fire that, during this war, the missing-nin Hiruko was actively working to finishing his Chimera Technique and have tracked Kakashi in order to brand him with his Puppet Curse. He claimed that, eventually, the Third Hokage ordered his assassination carried out by his former friends, the Sannin.