The war has converted the belligerent world to that kind of pacifism which consists in a grim determination that the present Armageddon shall never be repeated, however long it may be necessary to fight in order to ensure this outcome. To perpetuate the peace, however, a strong League of Nations is indispensable, and various plans for such a league are forming. Some of these rely on an extension of treaties of arbitration and conciliation, some would fortify these treaties by giving to the league a power to coerce recalcitrant members, and still others would create a world State with a central government, an army and a navy. The first question to be answered is, What kind of international union can be secured? since, in the case of any new league of this kind, the more ambitious the plan, the less probable it is that nations will adopt it. In many minds grave doubt exists whether even a modest plan will be carried into execution. In the face of this doubt I wish to express the audacious opinion that something having the characteristics of a league of peace is rapidly evolving and in all probability will, at the close of the war, require only a small modification to enable it to prevent, so long as it lasts, the recurrence of a great war on the Continent of Europe. It is not necessary to create a league of peace _de novo_ and without reference to combinations which now exist. Two great leagues have been formed, each embracing powerful States and each so firmly held together that it acts toward the outer world much as a single great empire would do. Since they are now waging against each other the greatest war in history, the conclusion is much too lightly reached that such unions are, _by their nature_, war-breeders. Defensive unions, however, are in line with the whole trend of political evolution. Great nations, created by combining smaller ones, are in the order of the day, and so are federations of a looser kind, such as those which preceded the German Empire and our own Federal State. [Sidenote: Even alliances tend to prevent war.] Every such consolidation involves a risk that, if a war occurs, it will be larger than it might otherwise be; but it reduces the frequency with which wars occur. Peace between great States continues through longer periods than it does between warring districts which later unite in such States. The prospect that peace shall ever be universal depends on its tendency to establish itself within larger and larger areas till it shall end by embracing the world. European wars have occurred in spite of alliances rather than because of them and the general effect even of imperfect unions has been to lengthen the intervals of peace. It is an even century since a war akin to this one was waging in Europe, and it is forty-four years since a war between any two great nations has taken place on that continent. The consolidating tendency in itself makes for peace.