The three daimyo who unified Japan were Oda Nobunaga, Hideyoshi, and Tokugawa Ieyasu.
The unification of Japan at the turn of the seventeenth century was a crucial event. It brought an end to a hundred years of warfare and to the constant military struggles among the feudal lords or daimyo.
Three famous daimyo spearheaded the unification in the late sixteenth century--and then, after the great Battle of Sekigahara in 1600, one man took control of all Japan. He was Tokugawa Ieyasu who became shogun in 1603.
While the Tokugawa period is well known as a long era of peace, perhaps we better understand these 250 years by focusing on two themes: order and change. Both sides of the Tokugawa years were crucial to the later making of modern Japan.
The Tokugawa period in itself, if I were to sum it up, would be characterized first by the word "order" and stability. The Tokugawa system had a penchant for order.
The central thought in the minds of the Tokugawa rulers was to prevent the country from lapsing into the kind of conflict that had existed.
There was more fighting in Japan during the sixteenth century than anywhere else in the world. The rulers of the Tokugawa were determined that that would not happen again.