On what date did Britain declare war on Germany following an " unsatisfactory reply " to the British ultimatum that Belgium must be kept neutral ?
It will claim that that Austrian action has been just of much of a surprise to it as to the other Powers , pointing out the fact that the Emperor is on his northern journey , and that the Prussian Minister of War , as well as the Chief of the Grand General Staff are away on leave of absence . ” However , on July 19th — four days before the ultimatum was presented — Jagow had asked all German Ambassadors the world over ( except for Austria - Hungary ) to state to their host governments that : “ If the Austro - Hungarian government is not going to abdicate forever as a great power , she has no choice but to enforce acceptance by the Serbian government of her demands by strong pressure and , if necessary , by resort to military measures . ” Subsequently , Jagow realized that his statement was incompatible with his claims of ignorance , thus leading to a hasty second dispatch claiming total ignorance of the Austrian ultimatum , but threatening “ incalculable consequences ” if any power tried to stop Austria - Hungary from attacking Serbia if the ultimatum were rejected .