Why did Japan’s emperors lose political power to the shoguns?

Japan’s emperors gradually lost effective political power as authority shifted first to powerful aristocratic families and later to the samurai, or warrior, class. In the late 12th century, Minamoto Yoritomo established a military government at Kamakura and became shogun in 1192. For most of the next seven centuries, shoguns and other military leaders exercised effective political control, while the emperor held little direct governing authority. The monarchy nevertheless retained considerable religious, cultural, and symbolic prestige, and the emperor remained an important source of political legitimacy.