In a 1996 essay in Foreign Affairs, the conservative authors William Kristol and Robert Kagan proposed a U.S. foreign policy of “benevolent global hegemony.” Scoffing at former President John Quincy Adams’s maxim that America “goes not abroad, in search of monsters to destroy,” they asked, “But why not? The alternative is to leave monsters on the loose, ravaging and pillaging to their hearts’ content, as Americans stand by and watch.” In Kristol and Kagan’s view, it was the United States’ responsibility to sally forth and slay—an argument they reprised years later as two of the biggest advocates for the Iraq war…