The two massive neighbouring nations of China and Russia have a shared history of distrust, annexation fears and ethnic differences. They share long borders and a Communist past, but in the late 1960s nearly came to blows, in which Russia threatened to use tactical nuclear weapons. China’s new wealth is becoming an attraction for retirees in the former Soviet nation, and they’re moving their roubles across the border – breaking tradition and creating new issues for a nation with it’s own migration problems.