"In the twenty-first century, the United States and China are destined to be the largest and strongest powers in the international system. China's rise has been proclaimed to be "peaceful," but in a prior century the American rise was scarcely pacific. The United States threatened war with Canada and Britain and actuallt fought against Mexico, annexing nearly half of that country in 1848. China was also vigilant and quick to react in its neighborhood. as U.S. forces neared the Yalu River in October 1950, China intervened in the Korean War, even though the United States possessed nuclear weapons and beijing did not. Neither state has been relaxed in the presence of challenging neighbors."