[2] The birth of the fudai daimyō class began as Tokugawa Ieyasu (徳川家康) rose to power in Japan in the 16th century.
Ieyasu became the most powerful lord in Japan following victory at the Battle of Sekigahara in October 1600, displacing the Toyotomi clan and unofficially founding the Tokugawa Shogunate as his de facto military government with himself as the Shōgun.
The fudai, in contrast to the tozama, typically ruled small domains in strategic locations along Japan's principal roads or in the Kantō region near Edo.
[3] High-ranking posts in the shogunate government (Bakufu) such as the rōjū, the wakadoshiyori, and the Kyoto Shoshidai normally went to fudai.
Two such men of fudai daimyō background were Ogasawara Nagamichi[7] and Itakura Katsukiyo,[8] who were two of the last rōjū, and actively worked for reform and strengthening of the ailing shogunate.
[9] Some remained neutral, while others (like the lords of Ōgaki and Tsu) switched allegiances and openly supported the new Imperial Japanese Army.
Ogasawara Nagamichi and Itakura Katsukiyo led small groups of their retainers during the fight against the Imperial forces.