ULTIMATUM, a formal intimation by one state to another state that unless the latter complies with certain terms certain consequences will follow. These consequences may be war or measures short of war; see INTERNATIONAL LAW (PUBLIC) ; PACIFIC BLOCKADE; REPRISALS; LAWS OF WAR.
A declaration of war may be either absolute or conditional. Under the customary law of nations prevailing at the time of the Russo-Japanese War, 1904, hostilities might be commenced with out any formal notice. In this conflict Japan was charged by Rus sia with making a treacherous attack. Japan replied that she had already severed diplomatic relations before taking action. This controversy led to the provisions contained in The Hague Conven tion III., 1907, whereby hostilities must not commence without previous and explicit warning in the form either of a declaration of war, giving reasons, or of an ultimatum with a conditional declaration of war. Further the existence of a state of war must be notified to the neutral Powers without delay, and does not take effect in regard to them until after the receipt of notification, which may be given by telegram. Nevertheless, neutral Powers
cannot rely on the absence of notification if it is clearly estab lished that they were aware of the existence of a state of war. In the World War, Austria-Hungary and Germany declared war by telegram. Great Britain verbally informed the German Govern ment that unless it withdrew its troops from Belgium, she would take steps to secure its neutrality. The German minister accepted this as a declaration of war. Italy verbally informed the Austro Hungarian ambassador at Rome that she considered herself in a state of war, and telegraphed the Italian ambassador at Vienna to make a similar declaration. This declaration with a reasoned statement was dispatched to Italian representatives abroad and to foreign governments. The United States declared a state of war with Germany by a resolution of Congress, approved by the Pres ident. The majority of other states at war with Germany made no formal declarations of war against her allies. Some merely broke off diplomatic relations. (H. H. L. B.)