Eastern Frontier Civil War

The Eastern Frontier Civil War (東国内戦, Tōgoku Naisen) was a war started after the death of the Gokage Sennin in the Eastern Frontier. Because the sage hadn't chosen a successor, the continent, and its many nations, erupted in war over who would bear the title of Gokage Sennin.

Prelude
Around the time the Sage of Six Path's was traveling the Five Great Nations, spreading his teachings of ninjutsu, a man arose in the Frontier spreading the same teachings as the sage. He would come to be known as the Gokage Sennin (五影聖人, Five Shadow Sage), and he was believed to have been related to the Sage in the west due to their similar dōjutsu. The Gokage preached the use of chakra, spurring the creation of ninja, samurai, and other chakra-using groups that followed his ideals. He had no successors upon his death, so the nations went to war over who should be the next Gokage Sennin. That war is still ongoing today.