The British government recognised and guaranteed the independence of the Karenni States in an 1875 treaty with Burmese King Mindon Min, by which both parties recognised the area as belonging neither to Burma nor to Great Britain. Consequently, the Karenni States were never fully incorporated into British Burma. The Karenni states formed for a time the "Kayah State" in post-independent Burma, but on 29 April 1959 both the Shan and the Kayah rulers formally surrendered their ruling powers to the Burmese government.