Bitchū Province in the context of "San'yōdō"

Bizen Province (備前国, Bizen no Kuni; Japanese pronunciation: [bʲiꜜ.(d)zeɴ, bʲiꜜ.(d)zen no kɯ.ɲi]) was a province of Japan in the area that is eastern Okayama Prefecture in the Chūgoku region of western Japan. Bizen bordered Bitchū, Mimasaka, and Harima Provinces. Its abbreviated form name was Bishū (備州). In terms of the Gokishichidō system, Bizen was one of the provinces of the San'yō circuit. Under the Engishiki classification system, Bizen was ranked as one of the 35 "superior countries" (上国) in terms of importance, and one of the "near countries" (近国) in terms of distance from the capital. The provincial capital was located in what is now the city of Okayama.

Mimasaka Province (美作国, Mimasaka no Kuni; Japanese pronunciation: [mʲi.maꜜ.sa.ka (no kɯ.ɲi)]) was a province of Japan in the area that is northern Okayama Prefecture in the Chūgoku region of western Japan. Mimasaka bordered Bitchū, Bizen, Harima, Hōki, and Inaba Provinces. Its abbreviated form name was Sakushū (作州). In terms of the Gokishichidō system, Mimasaka was one of the provinces of the San'yō circuit.

Under the Engishiki classification system, Mimasaka was ranked as one of the 35 "superior countries" (上国) in terms of importance, and one of the "near countries" (近国) in terms of distance from the capital. The provincial capital was located in what is now the city of Tsuyama.

The Ogasawara clan (Japanese: 小笠原氏, Hepburn: Ogasawara-shi) was a Japanese samurai clan descended from the Seiwa Genji. The Ogasawara acted as shugo (governors) of Shinano Province during the Sengoku period (c. 1185–1600), and as daimyō (feudal lords) of territories on Kyūshū during the Edo period (1600–1867).

During the Kamakura and Muromachi periods, the clan controlled Shinano province, while related clans controlled the provinces of Awa, Bizen, Bitchū, Iwami, Mikawa, Tōtōmi and Mutsu. According to some theories, the Miyoshi clan and the Mizukami clan were descendants of the Ogasawara clan.