However, if, in the course of events, the maintenance of the status quo in the regions of the Balkans or of the Ottoman coasts and islands in the Adriatic and in the Aegean Sea should become impossible, and if, whether in consequence of the action of a third Power or otherwise, Austria-Hungary or Italy should find themselves under the necessity of modifying it by a temporary or permanent occupation on their part, this occupation shall take place only after a previous agreement between the two Powers, based upon the principle of a reciprocal compensation for every advantage, territorial or other, which each of them might obtain.