Oda Nobunaga’s surprise victory over Imagawa Yoshimoto shattered a major regional power. Tokugawa Ieyasu (then Matsudaira Motoyasu) had fought under the Imagawa, so the Imagawa collapse opened space for him to shift alliances and pursue independence in Mikawa.
After the Imagawa setback, Ieyasu aligned with Oda Nobunaga, creating a durable partnership. The alliance let Ieyasu focus on consolidating Mikawa while Nobunaga expanded toward central Japan.
Ieyasu secured imperial court approval to use the surname “Tokugawa,” strengthening his political legitimacy. Claiming prestigious lineage mattered in a period when warlords competed not only by force, but also by status and recognition.
Takeda Shingen’s army beat Ieyasu’s forces, forcing Ieyasu to retreat and exposing the danger posed by powerful neighbors. The loss pushed Ieyasu to refine his defenses and coordinate more closely with allies.
Ieyasu and Nobunaga defeated Takeda Katsuyori at Nagashino, a major turning point in regional power. The win checked the Takeda threat and helped Ieyasu stabilize his position in central Japan.
After Toyotomi campaigns in the Kantō region, Ieyasu was moved there and made Edo Castle his headquarters. This shift gave him a large, strategically placed power base and set Edo on the path to becoming the political center of Japan.
Toyotomi Hideyoshi’s death reopened rivalry among leading warlords. Ieyasu emerged as a central figure in the contest over who would dominate the Toyotomi legacy and the national government.
At Sekigahara, forces aligned with Ieyasu defeated a coalition of Toyotomi loyalists led by Ishida Mitsunari. The victory made Ieyasu the strongest military and political leader in Japan, clearing the way for a new shogunate.
Emperor Go-Yōzei granted Ieyasu the title of shōgun, formally establishing Tokugawa rule at the national level. The new bakufu (military government) anchored authority in Edo while the emperor remained in Kyoto.
Ieyasu stepped down as shōgun and passed the title to his son Tokugawa Hidetada. This kept real power within the family while reducing the risk that rivals could exploit an uncertain transition.
Tensions with Toyotomi Hideyori, the heir of Hideyoshi, led Ieyasu to attack Osaka, the Toyotomi stronghold. The winter campaign initiated the decisive effort to eliminate the last major alternative center of national authority.
In the summer campaign, Tokugawa forces defeated Toyotomi troops near Osaka, bringing the conflict to a close. The Toyotomi leadership was destroyed, removing the main political and military challenge to Tokugawa rule.
Soon after Osaka, the shogunate issued the Buke Shohatto (Laws for the Military Houses), rules intended to limit daimyō behavior and reduce the risk of rebellion. These regulations helped turn Tokugawa victory into a stable governing system that could last beyond Ieyasu’s lifetime.
Ieyasu died after seeing the Toyotomi eliminated and the Tokugawa system firmly in place. His successors inherited a functioning shogunate centered on Edo, shaping the early Edo period’s long era of military peace under Tokugawa leadership.
Tokugawa Ieyasu's rise and the founding of the Tokugawa shogunate (1560–1615)