Over the past few months, we have been exploring the ideas of global leadership and of the U.S. role in the international system. We've also been examining the emergence of China as, by some accounts, a competitor to the United States in that role. We have sought to remain observers rather than advocates, trying to understand through a study of history and an assessment of current political, economic, security and social factors, how the structure of the global system has evolved, and in what direction it is likely headed. Our attempt has been to explore this broad theme not through the lens of "should," but of "was" and "is."...