As the dust settled after World War II, America controlled half the world’s manufacturing capacity. By the end of the Cold War it possessed nearly half the planet’s military forces, spread across eight hundred bases, and much of its wealth. Beyond what was on display, the United States had also built a formidable diplomatic and clandestine apparatus. Indeed, more than anything else, it is this secretive tier of global surveillance and covert operations that distinguishes the US from the great empires of the past.  But even as it has secured an unrivalled power network through satellites, drones and cyberwarfare, recent years have seen America’s share of the global economy diminish, its diplomatic alliances falter and its claim to moral leadership abandoned. Meanwhile, China is emerging as the world’s economic powerhouse, poised to integrate the ‘world island’ stretching from Shanghai to Madrid and lay claim to the South China Sea. The nineteenth century belonged to Britain and the twentieth to America. Will China take the twenty-first?