Kokang had been historically part of China for several centuries and is still claimed by the Republic of China to this day, but was largely left alone by successive governments due to its remote location. The region formed a "de facto" buffer zone between Yunnan province and the Shan States. The Yang clan, originally Ming loyalists from Nanjing, consolidated the area into a single polity. In 1840, the Yunnan governor granted the Yang clan the hereditary rights as a vassal of the Qing dynasty. After the British conquest of Upper Burma in 1885, Kokang was initially placed in China under the 1894 Sino-British boundary convention. It was ceded to British Burma in a supplementary agreement signed in February 1897.