After his father, Butsuma Senju, died, his older brother Hashirama became the leader of the Senju Clan. During the Warring States Period, under Hashirama's leadership, the Senju Clan fought countless battles against Uchiha Clan shinobi. Tobirama was a powerful warrior on the front lines. Facing thousands of Uchiha shinobi, he used his self-developed Flying Thunder God Technique to move between battlefields and cut down opponent after opponent, earning countless merits for the Senju Clan. Tobirama thus became famous throughout the shinobi world and was hailed as the fastest shinobi alive.
Afterward, the two great clans fought countless battles, yet neither could gain the upper hand. Until, in a later battle, Tobirama Senju seized the instant Uchiha Izuna thought he had won. Wielding a katana, Tobirama used the Flying Thunder God Slash, piercing Izuna's body with a strike too swift to evade. Izuna, who had never before been defeated, was severely wounded by Tobirama due to his carelessness. When Hashirama proposed that the two clans cooperate, Madara's younger brother Izuna vehemently opposed it. Madara therefore rejected Hashirama's proposal, then retreated with Izuna. The Uchiha shinobi present consequently surrendered their weapons to Hashirama and Tobirama.
In that battle, Tobirama shifted the evenly matched conflict between the two great clans into a situation where the Uchiha Clan was outnumbered and outmatched, laying the foundation for the Senju Clan's victory.
Not long afterward, the two strongest clans joined forces to establish Konohagakure. The other four nations followed the Land of Fire's example and formed their own shinobi organizations, ushering in an era in which the five great nations dominated the shinobi world. From the Warring States Period, when two shinobi clans fought to the death as bitter enemies, to the alliance between the Uchiha and Senju, they built a paradise for shinobi—a shinobi village