In the middle decades of the nineteenth century Japan was obliged to abandon institutions it had adopted in the early seventeenth century for the regulation of society, politics, and foreign policy. Where once a hereditary samurai class had ruled, supported by stipends provided by feudal lords subordinate to the Tokugawa shogun, a new government headed by the traditional monarchy evened out, and then abandoned, those social divisions. Several hundred mini-states ruled by the daimyo gave way to fifty prefectures governed from the center by state-appointed governors. Contacts with other countries once limited almost entirely to traders at Nagasaki were broadened, initially to a few treaty ports, and then everywhere, as Japan took part in the international order.

These were momentous changes. When they began Japan was a remote and inaccessible island state on the edge of Asia. After they were completed Japan had won membership in the circle of powers and joined its recent oppressors as an imperialist state in Asia. Domestic institutional changes, first begun as defensive moves to maintain national sovereignty, led inexorably to other steps that ended by transforming first Japan and then the Asian and world systems.

The chapters that follow, excerpted from Volume 5 of The Cambridge History of Japan, discuss some of these changes to show the nature of Japan's transformation and to show that these changes had their origins in earlier Japanese society.