Through the Cold War and beyond, Japan has been able to pursue a foreign policy centered on economic competition and cooperation rather than defense and security. External allies like the United States protected both the home islands and Japanese economic interests overseas. But things are changing, and Japan's mercantilist foreign policy will soon be insufficient to meet its strategic needs. China, of course, is the new factor. Since the end of the Cold War, Japan's neighbor has transformed from an isolated and impoverished pariah state into the world's second-biggest economy and Asia's largest. China has been the demographic center of East Asia for millennia and, for most of its history, it was also the regional hegemon. However, in the middle of the 19th century, internal and external pressures drove China into one of its periodic cycles of political fragmentation, social upheaval and introversion.