The first kingdom in Dehong was established by the ancestors of Dai ethnic minority in present Ruili City after 424BC. During the 4th Century BC, Sino-India economic trade began, benefiting from the opening of the Southwest Silk Road. After the Western Han Dynasty (206BC-24AD) exploited the southwest region of China, Dehong was brought into Yizhou Shire. During the Tang (618-907) and Song (907-1279) dynasties, it respectively belonged to the Nazhao State (738-937) and Dali State (937-1257). Dehong enjoys a subtropical monsoonal climate without winter chills nor intense summer heat. It has clear dry and humid seasons, with good rainfall.