The Japanese warrior chieftain Minamoto Yoritomo (1147-1199) founded Japan's first military government, or shogunate, in 1185 and thereby inaugurated the medieval period of Japanese history, which lasted until 1573.

In the 12th century, Japan was still ruled by the government of the imperial court in Kyoto and in particular by the courtier family of Fujiwara, which held the office of imperial regent and many other high ministerial positions at court. However, by regarding the provinces merely as a source of revenue from their private landed estates and by concerning themselves almost exclusively with life and affairs in the capital, the Kyoto courtiers sadly neglected provincial administration. The rise of a warrior class from about the 10th century stemmed directly from the need to provide order and control in the provinces.

By the 12th century, this emergent warrior class was dominated by two great clans, the Minamoto and the Taira, both...