From Wikipedia, the free encyclopedia

A tozama daimyo (外様大名) was a daimyo who was considered an outsider by the rulers of Japan. The term came into use in the Kamakura period and continued until the end of the Edo period.

The daimyo who submitted to the Tokugawa shogunate after the Battle of Sekigahara were classified as tozama. Many of the largest fiefs were ruled by tozama. The biggest was the Maeda clan of Kaga with a value of 1,000,000 koku. Others included the Shimazu family of Satsuma, the Mori, the Date, Hachisuka, and the Uesugi.

Tokugawa Ieyasu had treated the great tozama vassals amicably but later, between 1623 and 1626, Tokugawa Iemitsu was tolerant of them. Particularly in western Japan, the tozama daimyo heavily profited from foreign trade in the mid 17th century. Their growing success was a threat to the shogunate, which responded by preventing the ports of western Japan and Kyūshū from trading.

To keep the tozama in check, the shogunate stationed fudai daimyo in strategic locations, including along major roads and near important cities. The shogunate ordinarily did not appoint tozama to high positions within the government. These went instead to the fudai daimyo.

Tozama daimyo from Satsuma and Choshu (Shimazu and Mori clans respectively) were responsible for the fall of Tokugawa Shogunate during Bakumatsu era. They were not loyal to shogunate and saw opportunity to seize power during this time. Shimazu and Mori both united behind the Emperor of Japan to renew and westernize japan in the face of Western dangers. Afterwards, Shimazu and Mori clans had the most influence in military and government of Japan until after World War II.

The Aizu clan was much more loyal to Tokugawa Bakufu and fought to the end of the Boshin War against Satsuma-Choshu backed imperial forces. Aizu was defeated and pushed into Hokkaido to resist, so they were considered to be disloyal to Japan's emperor. However, in the 1920s, Aizu clan was pardoned by emperor and restored to honor.