Mark Galeotti The Sino-Russian border demarcated in 2008 is not just 2,672 miles (4,300 km) long, making it one of the longest in the world, but it stretches back into history and national mythology, as a dividing line between equally imperial but otherwise very different cultures. As well as marking a geopolitical division, it represents a massive economic opportunity to many but also a potential future threat. In 2004, Bobo Lo called “the development of the relationship with China . . . arguably the greatest Russian foreign policy success of the post-Soviet period.”1 Many in Moscow would agree, and the relationship with Beijing remains both a foundation stone of Russia’s geopolitical architecture and also a vital economic partnership. This is nonetheless tempered by a deep unease about the border and the rising power that lies beyond it, a concern about the shifting balance of economic and even military power and a sense that Russia remains fundamentally the front line of Europe versus Asia.2 While selling advanced weapons to China, for example, Russia still retains formidable forces in the Far East and regularly wargames how it would fight a war along the common border.