Four centuries before Tokugawa Ieyasu arrived at Edo, a fierce band of mounted warriors had already fortified the hill where Ieyasu would build his magnificent Edo Castle, and on which the Imperial Palace now stands.

In the late 12th century, the Edo clan, as these warriors called themselves, had moved south from Chichibu in present-day Saitama Prefecture led by their patriarch, Edo Shigetsugu. Seizing Edo, they rapidly built up their military presence in the southern Kanto Plain to such a point that, in 1180, Shigenaga, the second clan head, was asked by Minamoto Yoritomo (1147-99) to cooperate in his uprising against the great Taira family in Kyoto.

Shigenaga was not easily persuaded, but eventually lent his power to Yoritomo in overthrowing Taira rule. In appreciation, Yoritomo granted Shigenaga seven new estates in Musashi Province, including Kitami in what is now Tokyo's western Setagaya Ward.