"The transformation came on even more abruptly than is usually realized. World War I and the postwar revolutions still formed part of the nineteenth century. The conflict of 1914-18 merely precipitated and immeasurably aggravated a crisis that it had not created. But the roots of the dilemma could not be discerned at the time; and the horrors and devastations of the Great War seemed to the survivors the obvious source of the obstacles to international organization that had so unexpectedly emerged."