The Shogun-less Age
During the Epoch of the Warring Countries the Japanese state almost disintegrated, as the Daimyo (= great name) became hereditary princes and fought each other in civil wars. But during the sixteenth century three powerful Daimyo emerged to recreate the Japanese Empire :

Oda Nobunga (1534 - 82), who occupied Kyoto and eliminated the last Ashikaga Shogun.

Hideyoshi Toyotomi (1537 - 1598), Japan's most brilliant commander who broke the reign of the Daimyo.
By 1590 he had conquered the whole of Japan and he found himself suddenly with a superabundance of professional warriors who knew nothing but warfare. Partly to drain off their excess fighting spirit Hideyoshi decided to conquer the world, which for him meant the conquest of China.
In 1592 he invaded Korea, his passage to China. His armies overran almost all of Korea, but were stopped when they met the armies of China, which had come to the aid of its Korean satellite.

Ieyasu Tokugawa who defeated Hideyoshi's successor, set up a police state, transfered his capital to Edo (Tokyo), and initiated the Tokugawa Shogunate which ruled Japan peacefully for over two hundred years.

www link :
Unification of Japan Comprehensive web site about Nobunga and Hideyoshi.