In 1189, Minamoto no Yoritomo led a massive army into Oshu to destroy the Fujiwara clan. The Yanaginogosho site is believed to be the ruins of "Hiraizumi-no-tate," the administrative center from which four generations of the Fujiwara governed Oshu for roughly a century. Yoritomo's campaign brought down the fourth lord, Yasuhira, extinguishing Hiraizumi's political power forever.