This conversion was probably due to the fact that he had in his own mind worked out, as one of the essential bases of peace, to which he was then giving much thought, a mutual guaranty of territorial integrity and political independence, which had been the chief article of a proposed Pan-American Treaty prepared early in 1915 and to which he referred in his address before the League to Enforce Peace.

He appears to have reached the conclusion that a guaranty of this sort would be of little value unless supported by the threatened, and, if necessary, the actual, employment of force.
The President was entirely logical in this attitude.

A guaranty against physical aggression would be practically worthless if it did not rest on an agreement to protect with physical force.

An undertaking to protect carried with it the idea of using effectual measures to insure protection.

They were inseparable; and the President, having adopted an affirmative guaranty against aggression as a cardinal provision--perhaps I should say _the_ cardinal provision--of the anticipated peace treaty, could not avoid becoming the advocate of the use of force in making good the guaranty.
During the year 1918 the general idea of the formation of an international organization to prevent war was increasingly discussed in the press of the United States and Europe and engaged the thought of the Governments of the Powers at war with the German Empire.