In 1555, King Bayinnaung dislodged Shan king Sithu Kyawhtin from Ava. By 1557 he went on to conquer all of what would become known as the Burmese Shan states under his rule, from the Assamese border in the northwest to those in Kachin Hills and Shan Hills, including the two most powerful Shan states, Mohnyin and Mogaung. The Shan states were reduced to the status of governorships, but the Saophas were permitted to retain their royal regalia and their feudal rights over their own subjects. Bayinnaung introduced Burmese customary law and prohibited all human and animal sacrifices. He also required the sons of Saophas to reside in the Burmese king's palace, essentially hostages, in order to ensure the good conduct of their fathers and to receive training in Burmese court life. Burmese kings continued this policy until 1885 when the kingdom fell to the British. (The northernmost Shan states, in Yunnan, had already fallen to the Chinese Ming dynasty by the middle of the 15th century.)