Ultimatum[178] is the technical term for a written communication of one State to another which ends amicable negotiations respecting a difference, and formulates, for the last time and categorically, the demands to be fulfilled if other measures are to be averted. An ultimatum may be simple or qualified. It is simple in case it does not include an indication of the measures contemplated by the Power sending it; such measures may be acts of retorsion or reprisals, or hostilities. It is qualified if it includes an indication of the measures contemplated by the Power sending it, for instance a pacific blockade, occupation of a certain territory, or war. Now the ultimatum stipulated by article 1 of Convention III. must be a qualified one, for it must be so worded that the recipient can have no doubt about the commencement of war in case he does not comply with the demands of the ultimatum. For this reason, if a State has sent a simple ultimatum to another, or a qualified ultimatum threatening a measure other than war, it is not, in case of non-compliance, justified in at once commencing hostilities without a previous declaration of war. For this reason, Italy sent a declaration of war to Turkey in 1911, although an ultimatum threatening the occupation of Tripoli had preceded it.
Nothing is enacted by article 1 of Convention III. concerning the minimum length of time which an ultimatum must grant before the commencement of hostilities; this period may, therefore, be only very short, as, for instance, a number of hours. All the more is it necessary here likewise 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 an ultimatum without previously having tried to settle the difference concerned by negotiation.
It must be specially observed that the state of war following an ultimatum must likewise be notified to neutrals, for article 2 of Convention III. applies to this case also. And it must further be observed that, for the same reason as in the case of a declaration of war, an ultimatum containing a conditional declaration of war must be communicated to the other party by a written document.
Initiative hostile Acts of War.
§ 96. There is no doubt that, in consequence of Convention III. of the Second Peace Conference, the recourse to hostilities without a previous declaration of war or qualified ultimatum is forbidden. But the fact must not be overlooked that a war can nevertheless break out without these preliminaries. Thus a State might deliberately order hostilities to be commenced without a previous declaration of war or qualified ultimatum. Further, the armed forces of two States having a grievance against one another might engage in hostilities without having been authorised thereto and without the respective Governments ordering them to desist from further hostilities. Again, acts of force by way of reprisals or during a pacific blockade or an intervention might be forcibly resisted by the other party, hostilities breaking out in this way.
It is certain that States which deliberately order the commencement of hostilities without a previous declaration of war or qualified ultimatum, commit an international delinquency, but they are nevertheless engaged in war. Further, it is certain that States which allow themselves to be dragged into a condition of war through unauthorised hostile acts of their armed forces, commit an international delinquency, but they are nevertheless engaged in war. Again, war is actually in existence if the other party forcibly resists acts of force undertaken by a State by way of reprisals, or during a pacific blockade or an intervention. Now in all these and similar cases, although war has broken out without a previous declaration or qualified ultimatum, all the laws of warfare must find application, for a war is still war in the eyes of International Law even though it has been illegally commenced, or has automatically arisen from acts of force which were not intended to be acts of war.
However that may be, article 2 of Convention III. also applies to wars which have broken out without a previous declaration or qualified ultimatum, and the belligerents must without delay send a notification to neutral Powers so that these may be compelled to fulfil the duties of neutrality. But, of course, neutral Powers must in this case likewise, even without notification, fulfil the duties of neutrality if they are unmistakably aware of the outbreak of war.
II EFFECTS OF THE OUTBREAK OF WAR
Vattel, III. § 63—Hall, §§ 124-126—Westlake, II. pp. 29-32—Lawrence, §§ 143-146—Manning, pp. 163-165—Phillimore, III. §§ 67-91—Twiss, II. §§ 41-61—Halleck, I. pp. 526-552, and II. pp. 124-140—Taylor, §§ 461-468—Walker, §§ 44-50—Wharton, III. §§ 336-337A—Wheaton, §§ 298-319—Moore, V. § 779, and VII. §§ 1135-1142—Heffter, §§ 121-123—Lueder in Holtzendorff, IV. pp. 347-363—Gareis, § 81—Liszt, § 39, V.—Ullmann, § 173—Bonfils, Nos. 1044-1065—Despagnet, Nos. 517-519—Pradier-Fodéré, VI. Nos. 2694-2720—Nys, III. pp. 134-150—Rivier, II. pp. 228-237—Calvo, IV. §§ 1911-1931—Fiore, III. Nos. 1290-1301, and Code, Nos. 1439-1445—Martens, II. § 109—Longuet, §§ 8-15—Mérignhac, pp. 72-84—Pillet, pp. 42-59—Bordwell, pp. 200-211—Spaight, pp. 25-33—Ariga, §§ 13-15—Takahashi, pp. 26-88—Lawrence, War, pp. 45-55—Sainte-Croix, La Déclaration de guerre et ses effets immédiats (1892), pp. 166-207—Meyer, De l'interdiction du commerce entre les belligérants (1902)—Jaconnet, La guerre et les traités (1909)—Politis in Annuaire XXIII. (1910), pp. 251-282, and XXIV. (1911), pp. 200-223.