Battle of Ōshū in the context of "Dewa Province"

The Genpei War (源平合戦, Genpei Kassen, Genpei-Gassen; 1180–1185) was a national civil war between the Taira and Minamoto clans during the late Heian period of Japan. It resulted in the downfall of the Taira and the establishment of the Kamakura shogunate under Minamoto no Yoritomo, who appointed himself as Shōgun in 1192, governing Japan as a military dictator from the eastern city of Kamakura.

It followed a coup d'état by the Taira in 1179 with the removal of rivals from all government posts, and subsequently banishing them, and a call to arms against the Taira, led by the Minamoto in 1180. The ensuing Battle of Uji took place just outside Kyoto, starting a five-year-long war, concluding with a decisive Minamoto victory in the naval Battle of Dan-no-ura. However, it has been pointed out that the Battle of Ōshū in 1189 was the last battle during this period of civil war, as it completed Yoritomo's nationwide domination through the annexation of Northeast Japan.

The Northern Fujiwara (奥州藤原氏 Ōshū Fujiwara-shi) were a Japanese noble family that ruled the Tōhoku region (the northeast of Honshū) of Japan during the 12th century, 1094-1104, as their own realm.

They succeeded the semi-independent Emishi families of the 11th century, who were gradually brought down by the Minamoto clan loyal to the Imperial Court in Kyoto. They ruled over an independent region that derived its wealth from gold mining, horse-trading and as middlemen in the trade in luxury items from continental Asian states and from the far northern Emishi and Ainu people. They were able to keep their independence vis-a-vis Kyoto by the strength of their warrior bands until they were ultimately conquered by the Kantō samurai clans led by Minamoto no Yoritomo, in the Battle of Ōshū in 1189.