On 4 July 1914, Count Szogyeny, the Austro-Hungarian Ambassador to Germany (pictured), sent a message to Count Berchtold, the Austro-Hungarian Minister of Foreign Affairs. The Ambassador details his conversation with the German Undersecretary of State Arthur Zimmerman.
Count Szogyeny to Count Berchtold. Vienna, 4 July 1914.
Today, the Undersecretary of State casually asked me if I know anything of a step undertaken in Belgrade by the Imperial and Royal government reported by the papers. I gave an answer in the negative.
Herr Zimmerman assured me that he considered energetic action on the part of the monarchy, with whom the entire civilised world sympathised, perfectly justified, still he would advise great discretion and would not like to see that humiliating conditions were proposed to Servia.
Source: 1919 Austro-Hungarian Red Book, with minor edits.