Minamoto no Yoritomo was appointed as the first Shogun of the Kamakura Shogunate, an event that marked a pivotal transformation in governance in Japan. Following the Genpei War, which was fought between the Minamoto and Taira clans, Yoritomo emerged victorious, solidifying his power and authority. The title of Sei-i Taishōgun translated to 'barbarian-quelling generalissimo' and was historically given to military leaders tasked with defending the borders of Japan. This event catalyzed the end of the Heian era and the beginning of the Kamakura period, ushering in a new leadership structure dominated by the samurai class.

With Yoritomo’s ascension, the political landscape shifted dramatically. The imperial court, once the symbol of authority, found itself diminished as the military rulers, or shoguns, began to dictate the country’s trajectory. Yoritomo's governance entailed the establishment of a shogunate, where he instituted a system of feudalism, delegation of power, and local governance that allowed samurai to rule over the provinces. In establishing a capital in Kamakura, Yoritomo laid the foundational stones for the development of Japan's military governance and set precedents for future shogunates.

The implications of Yoritomo's appointment extended far beyond his lifetime, as it established a political order that would dominate Japan for centuries. This shogunate would influence socio-political structures, cultural developments, and the interaction between the ruling class and the imperial family, which would foster the samurai identity and shape Japanese society profoundly.