The greatest of the Western Allies is now the United States of America, and the Americans have come into this war simply for an idea. Three years and a half ago a few of us were saying this was a war against the idea of imperialism, not German imperialism merely, but British and French and Russian imperialism, and we were saying this not because it was so, but because we hoped to see it become so. To-day we can say so, because now it is so. In those days, moreover, we said this is the "war to end war," and we still did not know clearly how. We thought in terms of treaties and alliances. It is largely the detachment and practical genius of the great English-speaking nation across the Atlantic that has carried the world on beyond and replaced that phrase by the phrase, "The League of Nations," a phrase suggesting plainly the organization of a sufficient instrument by which war may be ended for ever. In 1913 talk of a World League of Nations would have seemed, to the extremest pitch, "Utopian." To-day the project has an air not only of being so practicable, but of being so urgent and necessary and so manifestly the sane thing before mankind that not to be busied upon it, not to be making it more widely known and better understood, not to be working out its problems and bringing it about, is to be living outside of the contemporary life of the world. For a book upon any other subject at the present time some apology may be necessary, but a book upon this subject is as natural a thing to produce now as a pair of skates in winter when the ice begins to bear.