How did Tokugawa unite Japan?

Tokugawa Ieyasu united Japan by establishing the Tokugawa shogunate in 1603, following his victory at the Battle of Sekigahara in 1600. He centralized power by creating a rigid social hierarchy and enforcing a strict policy of isolationism, which reduced the influence of foreign powers and internal conflict. The shogunate implemented a system of alternate attendance (sankin-kotai), requiring daimyo to spend time in Edo (modern-day Tokyo), which helped to control the regional lords and promote loyalty to the shogunate. This period of peace and stability, known as the Edo period, lasted over 250 years, solidifying Tokugawa's unification of Japan.