Chipwi is a small town in northeastern Myanmar’s Kachin State, perched on a bend of the meandering N’Mai River. For decades its people subsisted on the sale of walnuts, apricots, sour cherries and other produce to China’s Yunnan province, some 40 miles to the east via treacherous mountain roads and the Burmese border town of Pang War. But from 2010, the area’s economy began to change dramatically, transforming Beijing’s interests — and eventually its diplomacy — in the area.