The Danube in the First World War

The Danube flows from Germany through Austria, Hungary and the Balkans to the Black Sea. During the war its middle and lower course was one of the axes of the Balkan front. At Belgrade the river separated Austria-Hungary from Serbia, and further down, all the way to the delta, Romania from Bulgaria. Flotillas of river monitors fought on it, battles were fought for its banks, and whole armies crossed its current. From the autumn of 1915 it was also the route by which the Central Powers carried ammunition and supplies to Bulgaria and Turkey.

The border with Serbia (1914–1915)

The war was opened by the Danube Flotilla. According to a collector’s study of its field post, Austria-Hungary had 10 monitors during the war, a few patrol boats and auxiliary vessels. Shortly after midnight on 28–29 July 1914 three of them, Bodrog, Temes and Szamos, opened fire on Belgrade. For the following year the city lay on the front line, and the river served both sides. In the autumn of 1914 a Russian shipment of ammunition for the Serbs came down the Danube to the port of Prahovo. When, after the Battle of the Kolubara, a relative calm settled on the border, the Russians organised the transport of military equipment from the Entente countries through Serbia and its Danube ports to Russia.

In the autumn of 1915 the Central Powers came back to the river. On the night of 6–7 October German and Austro-Hungarian troops began crossing the Sava and the Danube, which at Belgrade was more than a kilometre wide. The landing in the city was supported by monitors, while the defenders of Belgrade were helped by the guns of a British naval mission. East of the city the 11th Army of General Max von Gallwitz was crossing, hampered from 12 October by the košava, a violent autumn wind from the east.

After a failed attempt on 22 October, the Austrians crossed at Orsova the next day, and on 26 October at Brza Palanka they joined up with the Bulgarians. The whole Serbian bank was now in the hands of the Central Powers. Minesweepers cleared the fairway through the Iron Gate, and on 5 November the first ships carrying ammunition reached the Bulgarian ports of Svishtov and Ruse; from there it went on by rail to Turkey, which was holding out at Gallipoli.

A river between Romania and Bulgaria (1916–1917)

When Romania entered the war, the river became a front again. On the night of 27–28 August 1916 Romanian boats attacked with torpedoes the Austro-Hungarian flotilla lying off Ruse, but sank only a barge. As early as 27 August the first Russian detachment crossed the Danube into the Dobruja, and on 4 September in the west the Romanians took Orsova, from where they could close navigation through the Iron Gate.

But the river proved a trap for the defenders of the right bank. The garrison of the fortress of Turtucaia had the wide, unbridged Danube at its back, and when on 6 September the Bulgarians and Germans broke through its defences, hundreds of soldiers drowned in the river. On 1 October the Romanians themselves crossed to the Bulgarian bank at Flămânda, but a storm broke the pontoon bridge, Austro-Hungarian monitors arrived, and after two days the crossing was called off. On 25 October the Bulgarians entered Cernavodă, the site of the great railway bridge over the Danube.

Finally, on 23 November, in fog, the troops of Field Marshal August von Mackensen crossed from Svishtov to the Romanian bank at Zimnicea, covered by the Danube Flotilla. The bridgehead opened the road to Bucharest. On 5 January 1917 the Central Powers took Brăila, the great grain port on the Danube, and the front came to rest on the lower Siret. The Armistice of Focșani of December 1917 halted the fighting on the river too, because it covered the Danube flotillas.

Treaties and the return of the Entente (1918)

The Peace of Bucharest of 7 May 1918 gave the Dobruja up to the Danube to the Central Powers and left Romania the delta. The European Commission of the Danube, which since 1856 had supervised navigation at the river’s mouth, was henceforth to consist only of the riparian and Black Sea states. Some of the Austro-Hungarian monitors sailed across the Black Sea to Odessa and Kherson to support the Austro-Hungarian troops in Ukraine.

In the autumn the river changed hands again. After the breaking of the Macedonian front and Bulgaria’s capitulation, the Serbian First Army entered Belgrade on 1 November, and the troops of the Central Powers fell back across the Danube and the Sava. On 10 November battalions of the French Army of the Danube crossed the river at Ruse and Romania re-entered the war. The Habsburg monarchy handed its navy over to the new state of the South Slavs, while the Danube Flotilla went to Hungary. Under the Belgrade convention, however, Hungary had to hand over its ships and monitors to the Allies and point out the mines in the Danube.