 Mito Castle changed hands several times after that; a "daimyō" named Satake Yoshinobu won it in the mid-16th century, but he was forced to surrender it to Tokugawa Ieyasu in 1603 after the Battle of Sekigahara.Ieyasu's son Tokugawa Yorifusa was then given Mito Castle, becoming head of one of the three "gosanke" branches of the clan qualified to provide a new shōgun should the main family line fail.During this period, Mito was the seat of the so-called Mito School, a congregation of nativist scholars of Confucian persuasion led by Aizawa Seishisai, who during the 18th and 19th centuries advocated Western learning as a means not only to further Japanese technological development and international strength, but as means to prove Japanese uniqueness and superiority among nations.