Second Great Shinobi War (Earth-2165)

The Second Great Shinobi War was the second great war between the majority of the shinobi nations on Earth. Born from the scars and catasthrope of Fire Lord Sōzin instigated |first incited conflict, the Second Great Shinobi War proved to be the worst conflict in history, claiming hundreds of millions of lives. They mostly took place in minor nations, such as the Land of Storms, which left them devastated and effectively broken after the end of the war. Although no official winner was declared, the Land of Fire was the most favored and least affected among the five great nations.

Background
The First Great Shinobi War ended in 122 AG with the death of Fire Lord Sōzin and an armistice treaty, but left the five great nations extremely weakened and economically broken. The treaty ensured an uneasy period of relative peace, but thirty years later, the economic and social disparity between the nations became violent. Factions were formed, and under the pretext of expending rights, the countries started to form their own militaries to expand to neighbour territories, starting a new war which, like the first, would last a total of one hundred years.

It was during this time that the Land of Fire and the Land of Earth upgraded and increased their military force to become the present war machines they are known to be.

Aftermath
Staying true to the worst fears of the nations, the Second Great Shinobi War brought the deaths of even more individuals and the birth of new heroes; it was during the war that the legendary Sannin were formed, a nickname they received from Hanzō the Salamander during a skirmish on Amegakure. Tsunade, the future Fifth Hokage, became widely known as the greatest healer in the world, where she countered all poisons created by Chiyo, and her discoveries and ideas in the field of medicine revolutionized the way shinobi could use bending abilities in battle, with special forces she herself trained, which proved to be a success with an increase of survival rates and mission effectiveness.

The war saw a large number of deaths; Tsunade's lover, Dan Katō, died in battle, as well as the parents of Sasori, prompting him to eventually leave his home at the Sunagakure and become a member of the Akatsuki. Chiyo swore vengeance on the infamous Sakumo Hatake, the White Fang of the Leaf, who took the lives of Sasori's parents. Sakumo failed during a mission and eventually commited suicide, which shaped his son Kakashi in the years to come. Nagato and Konan, two children from the Hidden Rain, were left orphaned after the war, leading Iroh to take care of them for some time. Nagato grew to disdain the war for the suffering it caused, and so he and Konan grew to found the Akatsuki, bent on ending all conflicts in the world.