On 25 July 1914, the Austro-Hungarian Ambassador to Serbia, Baron Wladimir Giesl (pictured), sent a coded telegram to the Austro-Hungarian Minister of Foreign Affairs, Leopold Count Berchtold. In his telegram, Giesl informs Berchtold of the mood in Belgrade as the Austro-Hungarian ultimatum to Serbia is about to expire. Giesl describes the perceived evacuation of Belgrade in preparation for war.
Baron von Giesl to Count Berchtold. Belgrade-Semlin, 25 July 1914.
[The Serbian] Council of Ministers met last night and again early this morning. There are several reports that the answer to our Note [i.e. the Austro-Hungarian ultimatum to Serbia] will be given to me before the term has expired. I hear that a Court-train is being put together. Money from the National Bank and from the railways, as also the documents of the Ministry of Foreign Affairs are to be sent to the interior of the country. Some of my diplomatic colleagues are of opinion that they must follow the Servian government. In the Russian legation, packing is busily going on.
The garrison has left the city in field equipment. The ammunition depots of the fortress were evacuated. The sanitary columns have left Belgrade in a southern direction. In accordance with the instructions received, we will, in case of a rupture, leave Belgrade with the 18:30 train and will send instructions to the consulates, as directed.
Source: 1919 Austro-Hungarian Red Book, with minor edits.