From the 1850s until the mid-twentieth century, a period marked by global conflicts and anxiety about dwindling resources and closing opportunities after decades of expansion, the frontier became a mirror for historically and geographically specific hopes and fears. From Asia to Europe and the Americas, countries around the world engaged with new interpretations of empire and the deployment of science and technology to aid frontier development in extreme environments. Through a century of political turmoil and war, China nevertheless is the only nation to successfully navigate the twentieth century with its imperial territorial expanse largely intact. In Birth of the Geopolitical Age, Shellen Xiao Wu demonstrates how global examples of frontier settlements refracted through China's unique history and informed the making of the modern Chinese state. Wu weaves a narrative that moves through time and space, the lives of individuals, and empires' rise and fall and rebirth, to show how the subsequent reshaping of Chinese geopolitical ambitions in the twentieth century, and the global transformation of frontiers into colonial laboratories, continues to reorder global power dynamics in East Asia and the wider world to this day.