Toyotomi Hideyoshi learned of his lord’s death while he was besieging Takamatsu Castle, a Mori stronghold. He concluded piece with them before rushing back to subdue Mitsuhide’s forces who were trying to gain legitimacy from the Emperor and support from other daimyos. Toyotomi Hideyoshi defeated Mitsuhide’s forces in the Battle of Yamazaki. Mitsuhide fled the battlefield and was said to have been killed by a bandit.
Toyotomi became a de facto leader of his lord’s forces after successfully avenging his lord’s death. However, another senior Oda general, Shibata Katsuei opposed him by championing Oda Nobutaka, Nobunaga’s second son.
In the battle of Shizugatake in the year 1583, Toyotomi forces utterly defeated Shibata Katsuei’s men. Katsuei and Oda Nobutaka were forced to commit suicide after Toyotomi’s victory. After this victory, Toyotomi Hideyoshi virtually became the undisputed leader of the late Nobunaga’s forces.
However, Tokugawa Ieyasu tried to challenge Hideyoshi’s authority. In 1584, Tokugawa and Toyotomi forces fought at the Battle of Komaki-Nagakute. The commander of Toyotomi forces, Ikeda Tsuneoki was killed by a certain Nagai Denpachiro, a common foot soldier of Tokugawa army. This battle was considered to have ended in a draw as neither side won. Ieyasu reluctantly submitted to Toyotomi Hideyoshi after he realized he could not win this battle.
Toyotomi continued the reunification of the country that was initiated by Oda Nobunaga. He subdued the Chosokabe clan in Shikoku island and the Shimazu clan in Kyushu island. In 1590, Toyotomi and Tokugawa forces attacked Odawara, the capital of the Hojo clan in Kanto. After besieging Odawara for months, Hojo Ujimasa, the head of the Hojo clan surrendered. While the defenders were spared, Hojo Ujimasa and his younger brother, Hojo Ujiteru was forced to commit seppuku. Ujimasa’s son, Ujinao was spared as he was married to a daughter of Tokugawa Ieyasu.
Tokugawa Ieyasu was offered 8 provinces in Kanto that encompassed former Hojo domains in exchange for the 5 provinces that was under him. Ieyasu accepted the offer and built Edo Castle in Edo (Tokyo today). Ieyasu now controlled vast area in Kanto, a strategic region of Japan.