Nine-Tailed Demon FoxEdit
13 years ago, the Hidden Leaf Village was attacked by the Nine-Tailed Demon Fox (Kyubi). Causing much destruction and killing many of the village's shinobi. It was eventually defeated and sealed into the newborn child Uzumaki Naruto by the village's most powerful shinobi and leader, the 4th Hokage. The 4th Hokage died soon after the battle ended, because of the Ninjutsu he used. Sacrificing his own ife and fulfilling his duty as the village's Hokage.
Since that time, power has returned to the 3rd Hokage, who is later on killed by Orochimaru during the combined attack of both the conspiring Hidden Sand and Orochimaru's Hidden Sound. Tsunade, one of the Legendary Sannin takes on the role of the Figth Hokage at that point