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.
Particular attention must be paid to the fact that, in case of a declaration of war, the war, as between the belligerents, is considered to have commenced with the date of its declaration, although actual hostilities may not have been commenced until a much later date. On the other hand, as regards relations between the belligerents and neutrals, a war is not considered to have commenced until its outbreak has either been notified to the neutrals or has otherwise become unmistakably known to them. For this reason, article 2 of Convention III. enacts that the belligerents must at once after the outbreak of war notify[177] the neutrals, even if only by telegraph, and that the state of war shall not take effect with regard to neutrals until after they have received notification, unless it be established beyond doubt that they were in fact aware of the condition of war.