“Ask big questions.” If there is one piece of advice I’ve taken to heart, this is it. Big questions concern important sub- jects; their answers profoundly shape how we understand the evolution and operation of the world around us. Furthermore, big questions end in big question marks. We genuinely don’t know the answers when first undertak- ing to study them. As a result, big questions offer both the opportunity to make a scholarly contribution and the intellectual motivation for a curious mind to persevere through an objectively daunting amount of research. This book was born from my nagging unease that the modern world would look very different if its first unrivaled superpower had continued pursuing con- quest instead of outlawing it. It stemmed as well from my curiosity about why the most powerful country in the history of the world had lost interest in something that many other great powers as well as its own early leaders
found so appealing.