How was the unification of japan achieved?

Oda Nobunaga, Toyotomi Hideyoshi and Tokugawa Ieyasu were the shoguns that were credited for unifying Japan in the late 1500's. Oda Nobunaga reduced influence of Buddhist control over Japan politics and started unifying Japan. Toyotomi Hideyoshi continued to unify Japan, changed tax payments from money to rice, created a standing army and made a rule stating that you can't be part farmer or part samurai. Tokugawa Ieyasu established his government base in Edo and finalized the unification of Japan.