Naruto Goes Back In time
Naruto (Canon) by Masashi Kishimoto
Chapter 2: Uchiha and Senju Alliance
Indra Otsutsuki was the oldest son of the Sage of Six paths. It was through him that the Uchiha clan had inherited the Sage eyes powers, granting them powerful spiritual energy and chakra. The way to activate this eye is to understand ones emotions such as hate, anger, and so on. It began by the curse of hatred; this was first seen in Indra at a young age and soon began to become a prodigy in the arts of the shinobi. This eye power was called the Sharingan (the copy wheel eye). It's been a genetic trait called dojutsu or kekkei genkai of the Uchiha clan that appears to certain members of the clan. The way it activates is by experiencing a powerful emotional condition. Their brain release a special form of chakra that affects the optic nerves transforming the eye into the copy wheel eye, also known as sharingan. This eye power is best described as the eye that reflects the heart.
On one hand we have the Uchiha clan descendants of Indra Otstutsuki and their inheritance the sharingan. While on the other hand, we have Asura, the younger son of the sage of six paths. He is the younger brother of Indra and ancestor of both the Senju clan as well as the Uzumaki. In his early childhood Asura was living on the big brothers shadows Indra the genius. Later on he realize the value of others and the power of his friends and allies he made, and eventually he awakened his own power which equaled that of his brothers (Indra).
It was on his death that Hagoromo (the original sage of six paths) had selected the younger brother Asura, to carry out his dream of peace and understanding in the world. Due to the reasoning of his father's choice, Indra raged and angry that he wasn't chosen to lead was manipulated into fighting Asura. And thus we come to the conclustion of the clan wars between the descendants of Indra, or the descendants of the Senju clan (Asura's descendants)…
It was sometime after that the wars had been more repetitive, this time of period was called Warring States Period. The countries of the world were small, if any there were called villages, clans to be exact. One fight after another, the ultimate rivals, senju and uchiha clans, were consider to be both the strongest. This was until one man named Madara Uchiha came forth and was born, along from the Senju clan Hashirama Senju. Both men had met once upon a time when they were younger, unaware of each other identities; they quickly became friends, bonding over the deaths of the siblings because of war. They both desire to protect the rest of the siblings, without doubt or fear, it was a dream to create a world of peace where the children would not need to fight. It was some time later, that they both had learned each others identities and both became aware of the danger they were putting themselves in. And thus they stop with their meetings, eventually meeting on the battlefield for more than a few years. Some time later each became a leader of the clan, with Madara having the Mangekyo Sharingan, and advance copy of the original sharingan. While Hashirama had become one with nature, a sage if so be it. It was some time later, that Izuna (Madara's younger brother), had told him to continue the fight and thus gave his sharingan to his older brother, through a powerful procedure, and thus the Mangekyo Sharingan was born. It was through their last fight that Madara and the rest of he Uchiha they had become tired of their wars, and soon a treaty was born.
It was due to this day, the village of the hidden leafs was born. Soon other clans wanted to join the hidden leaf, such as the Sarutobi clan, Nara clan, Yamanaka clan and so forth. And thus this country became known as the land of fire. It was some time later, other clans started to copy the hidden leafs village system. And soon there were to be the iron land (Neutral), the hidden leaf village, the land of rock, the land of fire, the land of water, and least the land of earth.