Oda, Toyotomi and Tokugawa

Oda Nobunaga was the well-known lord of the Nagoya area (once called Owari Province) and an exceptional example of a samurai of the Sengoku Period. He came within a few years of, and laid down the path for his successors to follow, the reunification of Japan under a new Bakufu (Shogunate).

Oda Nobunaga made innovations in the fields of organization and war tactics, heavily used arquebuses, developed commerce and industry and treasured innovation. Consecutive victories enabled him to realize the termination of the Ashikaga Bakufu and the disarmament of the military powers of the Buddhist monks, which had inflamed futile struggles among the populace for centuries. Attacking from the "sanctuary" of Buddhist temples, they were constant headaches to any warlord and even the emperor who tried to control their actions. He died in 1582 when one of his generals, Akechi Mitsuhide, turned upon him with his army.

Importantly, Toyotomi Hideyoshi (see below) and Tokugawa Ieyasu, who founded the Tokugawa Shogunate, were loyal followers of Nobunaga. Hideyoshi was brought up from a nameless peasant to be one of Nobunaga's top generals and Ieyasu had shared his childhood with Nobunaga. Hideyoshi defeated Mitsuhide within a month and was regarded as the rightful successor of Nobunaga by avenging the treachery of Mitsuhide.

These two were gifted with Nobunaga's previous achievements on which build a unified Japan and there was a saying: "The reunification is a rice cake; Oda made it. Hashiba shaped it. At last, only Ieyasu tastes it."[citation needed] (Hashiba is the family name that Toyotomi Hideyoshi used while he was a follower of Nobunaga.)

Toyotomi Hideyoshi, who became a grand minister in 1586, himself the son of a poor peasant family, created a law that the samurai caste became codified as permanent and hereditary, and that non-samurai were forbidden to carry weapons, thereby ending the social mobility of Japan up until that point, which lasted until the dissolution of the Edo Shogunate by the Meiji revolutionaries.

It is important to note that the distinction between samurai and non-samurai was so obscure that during the 16th century, most male adults in any social class (even small farmers) belonged to at least one military organization of their own and served in wars before and during Hideyoshi's rule. It can be said that an "all against all" situation continued for a century.

The authorized samurai families after the 17th century were those that chose to follow Nobunaga, Hideyoshi and Ieyasu. Large battles occurred during the change between regimes, and a number of defeated samurai were destroyed, went ronin or were absorbed into the general populace.