The subject of this volume is medieval Japan, spanning the three and a half centuries between the final decades of the twelfth century when the Kamakura bakufu was founded and the mid-sixteenth century during which civil wars raged following the effective demise of the Muromachi bakufu. The historical events and developments of these colorful centuries depict medieval Japan's polity, economy, society, and culture, as well as its relations with its Asian neighbors. The major events and the most significant developments are not difficult to summarize.

This was the period of warriors. Throughout these centuries, the power of the warrior class continued to rise, and one political result of this development was the formation of two warrior governments, or bakufu. The first, the Kamakura bakufu, founded in the 1180s, was not able to govern the nation single-handedly. In several important respects, it had to share power with the civil authority of the tennō – usually translated as the emperor – and the court. But under the second warrior government – the Ashikaga bakufu that came into being in 1336 and was firmly established by the end of the fourteenth century – the warrior class was able to erode the power of the civil authority. During the first half of the fifteenth century, when the bakufu's power was at its zenith, the warrior class governed the nation in substantive ways. Although the civil authority did not lose all its power and continued to help legitimize the bakufu, it was manipulated and used to serve the bakufu's own political needs almost at will.