This commentary was published in Foreign Policy on 04/04/2011
The United States started out as 13 small and vulnerable colonies clinging to the east coast of North America. Over the next century, those original 13 states expanded all the way across the continent, subjugating or exterminating the native population and wresting Texas, New Mexico, Arizona and California from Mexico. It fought a bitter civil war, acquired a modest set of overseas colonies, and came late to both world wars. But since becoming a great power around 1900, it has fought nearly a dozen genuine wars and engaged in countless military interventions.