A declaration of war is a communication of one State to another that the condition of peace between them has come to an end and a condition of war has taken its place. In former times declarations of war used to take place under greater or lesser solemnities, but during the last few centuries all these formalities have vanished, and a declaration of war nowadays may take place through a simple communication. The only two conditions with which, according to article 1, declarations of war must comply are, that they must be unmistakable, and that they must state the reason for the resort to arms. No delay between the declaration and the actual commencement of hostilities is stipulated, and it is, therefore, possible for a Power to open hostilities immediately after the communication of the declaration of war to the enemy. All the more is it necessary to emphasise that there could be no greater violation of the Law of Nations than that which would be committed by a State which sent a declaration to another without previously having tried to settle the difference concerned by negotiation. However this may be, the question as to the way in which the communication of the declaration of war is to be made requires attention. Since there is nowhere a rule expressly formulated according to which the declaration must be communicated in writing, it might be asserted that communication by any means, be it by a written document, by telegraph or by telephone message, or by direct word of mouth, is admissible. I believe that such an assertion cannot be supported. The essential importance of the declaration of war and the fact that according to article 1 of Convention III. it must be unmistakable and must state the reason for the resort to arms, would seem to require a written document which is to be handed over to the other party by an envoy. Further, the fact that article 2 of Convention III. expressly enacts that the notification of the outbreak of war to neutrals _may even be made by telegraph_, points the same way, for the conclusion is justified that the declaration of war stipulated as necessary by article I may _not_ be made by telegraph. And if a telegraph message is inadmissible, much more are telephone messages and communications by word of mouth. Moreover, the practice of the States throughout the last centuries has been to hand in a written declaration of war, when any declaration has been made.