Today's North Atlantic Treaty Organization, with nearly thirty members and a global reach, differs strikingly from the alliance of twelve created in 1949 to -keep the Americans in, the Russians out, and the Germans down.- These differences are not simply the result of the Cold War's end, 9/11, or recent twenty-first-century developments but represent a more general pattern of adaptability first seen in the incorporation of Germany as a full member of the alliance in the early 1950s. Unlike other enduring post-World War II institutions that continue to reflect the international politics of...