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One cannot designate a "first" samurai unique, as the category gradually took shape between the 9th and 11th centuries. When referring to an imperial general, Sakanoue no Tamuramaro, who was active in the early Heian period, is the first famous name to bear the title of Sei-i Taishōgun and to lead the campaigns in the North. If we talk about the first ones bushi provincial leaders, who were political actors in their own right, Taira no Masakado, a rebel leader of the 10th century, represents a founding milestone, known thanks to the Shōmonki. Modern historiography, from Karl F. Friday to Cambridge History of Japan, emphasizes the gradual emergence of warriors, long referred to as bushi, tsuwamono or mononofu, before the word samurai from saburau ("to serve") really applies... In other words, Tamuramaro and Masakado embody two different "firsts," depending on the definition used.

On June 28, 1575, the Nagashino plain became the scene of a major strategic turning point in Japanese military history. Faced with the legendary cavalry of the Takeda clan, Oda Nobunaga and Tokugawa Ieyasu implemented an unprecedented defense strategy: organized firepower.
On the banks of the Rengogawa River, more than 3,000 ashigaru arquebusiers were lined up in three rows behind bamboo palisades. Each row fired in turn while the others reloaded, creating a continuous rain of lead. As a result, the Takeda cavalry's frontal charge, which had been invincible until then, was broken with devastating losses.
This battle marked the beginning of the end of the dominance of massive sword charges in favor of strategy and modern weaponry. It symbolized the rise of Oda Nobunaga and the decline of the great conservative feudal clans.