
Koga Domain

 was a feudal domain under the Tokugawa shogunate of Edo period Japan. It is located in Shimōsa Province, Honshū. The domain was centered at Koga Castle, located in what is the city of Koga in Ibaraki Prefecture.
History.
During the Muromachi period, Koga was the seat of the Kantō kubō, under the Ashikaga clan, who vied with the Uesugi clan and with the Later Hōjō clan for control of eastern Japan. Ashikaga Ujinohime was the last Koga-kubo and owner of Koga domain of the Ashikaga lineage.
When Toyotomi Hideyoshi defeated the Hōjō at the Siege of Odawara, the area fell into his hands, and was subsequently assigned (along with the rest of the Kantō region) to Tokugawa Ieyasu. Ieyasu assigned Koga Castle to his grandson-in-law, Ogasawara Hidemasa as "daimyō" of Koga Domain, with assessed "kokudaka" of 30,000 "koku".
Afterwards, the domain was reassigned every couple of generations to a large number of "fudai daimyō" clans, spending the longest time under the control of the Doi clan (1633–1681, 1762–1871).
During the Boshin War, the Tokugawa shogunate ordered the domain to provide guards on the foreign settlement at Yokohama. However, the domain capitulated almost immediately on the approach of the imperial forces. The final "daimyō" of Koga, Doi Toshitomo, served as domain governor until 1871, and was awarded the title of "shishaku" (marquis) under the "kazoku" peerage system. Koga Domain subsequently became part of Ibaraki Prefecture.
Bakumatsu period holdings.
As with most domains in the han system, Koga Domain consisted of several discontinuous territories calculated to provide the assigned "kokudaka", based on periodic cadastral surveys and projected agricultural yields.