On 8 July 1914, the Austro-Hungarian Minister of Foreign Affairs Count Leopold Berchtold wrote to the Hungarian Premier Istvan Tisza. In his letter Berchtold details his conversation with the German Ambassador to Austria-Hungary.
Letter from Count Berchtold to Count Tisza. Vienna, 8 July 1914.
Tschirschky [the German Ambassador] has just left me, he told me that he had received a telegram from Berlin, by which his Imperial master instructs him to declare emphatically that in Berlin an action of the monarchy against Servia is fully expected and that Germany would not understand why Ave should neglect this opportunity of dealing a blow.
My remark that in taking a decisive resolution we should consider it of the greatest importance to know how far we could rely upon Germany’s influence being used in Roumania, and what result we might hope for, was answered by the ambassador to the effect that Berlin thinks it is altogether out of question that Roumania would in this case act against the monarchy. Emperor William has already addressed a letter on the subject to King Carol and we might be very sure that it left nothing to be desired in plainness of speech!
The ambassador’s further remarks showed me that Germany would consider further negotiating with Servia a confession of weakness on our part, and this would damage our position in the Triple Alliance and might influence Germany’s future policy.
Tschirschky’s remarks impressed me so much, that I thought they might in some degree influence your ultimate decisions, and for this reason I am informing you without delay and begging you, if you are of the same mind, to telegraph me (in cypher) while I am at Ischl, where I stay all tomorrow and shall be glad to be your interpreter with His Majesty.
Source: 1919 Austro-Hungarian Red Book, with minor edits