Austro-Hungarian artillery shells Belgrade

A few hours after Austria-Hungary declared war on Serbia, the first shots were fired. Shortly after midnight on the night of 28–29 July 1914 the river monitors of the Austro-Hungarian Danube Flotilla – Bodrog, Temes and Szamos – opened fire towards Belgrade. The salvoes from the deck of the Bodrog are regarded as the first shots of the First World War.

The capital of Serbia lay right on the border, at the confluence of the Sava and the Danube. On the other bank of the Sava stood Austro-Hungarian Zemun, and the two cities were linked by a railway bridge. The Serbs expected the enemy to try to use it. That same night a detachment under Major Vojislav Tankosić blew up the bridge before the Austrians could reach it. Tankosić was the very officer whose arrest had been demanded by the Austro-Hungarian ultimatum of 23 July, which accused him of taking part in preparing the Sarajevo assassination.

At dawn artillery batteries positioned in and around Zemun, including heavy howitzers and mortars, joined the bombardment. Shells struck schools, banks and hotels. Human losses that day were small, but the symbolic significance of the shelling was enormous: for the first time in this war, artillery fire fell on a European capital.

The shelling of Belgrade did not yet mean an invasion. The Austro-Hungarian army needed time to complete its mobilisation, and the actual offensive against Serbia began only on 12 August. The city, however, remained under fire for weeks to come. In December 1914 Austro-Hungarian troops briefly occupied Belgrade, but after their defeat at the Battle of the Kolubara they had to leave it after less than two weeks.

The night of 28–29 July closed the era of notes and ultimatums. From then on the Austro-Serbian conflict was a real war, and its further course was to be decided not only by the armies of Austria-Hungary and Serbia but also by decisions taken in St Petersburg, Berlin, Paris and London.