Battle of the Drina begins

On 8 September 1914, after night crossings of the border river Drina, Austro-Hungarian troops began the fight for the hills of western Serbia. So began the Battle of the Drina, a series of bloody clashes in the mountains above the river which lasted almost four weeks and turned into trench warfare. The British chronology of the war records its beginning under this date. The Austro-Hungarian 5th Army made its first attempts to cross as early as 7 September, and the Polish Wikipedia dates the battle from 6 September, including in it the Serbian offensive in Syrmia.

The crossings

General Oskar Potiorek began the second invasion of Serbia with two armies. On the lower Drina, opposite the lowland Mačva, the 5th Army of General Liborius von Frank attacked. Further south, on the middle course of the river, the 6th Army, commanded by Potiorek himself, attacked.

In the northern sector the crossings went badly for the Austro-Hungarians. In early autumn the Drina was shallow in many places and the soldiers waded across, but the Serbian 2nd Army of General Stepa Stepanović was waiting for them in trenches on the other bank. According to various estimates the 5th Army lost about 4,000 men in the first clashes, and some of its units had to withdraw. It held only small bridgeheads.

In the south, on 8 September, the XV and XVI Corps of the 6th Army crossed the Drina on the stretch from Zvornik to Ljubovija (PL). The mountain brigades, accustomed to fighting in such terrain, surprised the weaker Serbian 3rd Army of General Pavle Jurišić Šturm. Within a few days the Austro-Hungarians had forced their way onto the mountain ridges running along the river: Gučevo above Loznica, Boranja and Jagodnja. From them roads led into the interior, towards Krupanj and Valjevo.

Mountains instead of plains

The fighting on the Drina looked different from the August battle on Mount Cer. It took place in steep, wooded mountains cut by deep valleys, where it was difficult to move artillery and supplies. Every ridge and every peak became a battlefield of its own. Both sides quickly began to dig trenches, and in some sectors they were only a few dozen, or even a few, metres apart.

The chief of staff of the Serbian army, Vojvoda Radomir Putnik, judged that the threat from the west outweighed the gains of the expedition into Syrmia then under way. On 11 September he ordered a withdrawal behind the Sava, and sent the troops of the 1st Army of General Petar Bojović on a forced march to the Drina, against the 6th Army.

Mačkov Kamen and trench warfare

From mid-September the Serbs counter-attacked. They retook some of the lost hills, but failed to push the enemy back into the river. The climax of the fighting was the battle of several days for Mačkov Kamen, a peak in the Jagodnja range, which changed hands many times on 20–22 September. On the evening of 22 September the Serbs withdrew from the peak. According to Serbian figures about 2,000 dead of both sides were left on the battlefield, later buried in the ossuary by the church in Krupanj, and the losses of the Serbian divisions in killed and wounded ran into thousands.

After these clashes the front stabilised on the mountain ridges above the Drina. The Serbs fought without enough ammunition, often in civilian clothes and opanci instead of boots. At the same time Serbian and Montenegrin troops struck into eastern Bosnia and on 14 September took Višegrad, but did not hold it for long. The end of the Battle of the Drina is usually put at 4 October. Trench warfare in these mountains, however, went on until November, when Potiorek launched his third offensive.

Significance

The Battle of the Drina brought neither side a decision. Austria-Hungary halted the Serbian offensive in Syrmia and kept its bridgeheads on the Serbian bank, but did not break the defence. Serbia held out, but paid for it with enormous losses and exhausted its stocks of ammunition, which weighed heavily on the course of the fighting in the autumn. The Serbs call the fighting on Gučevo the first trench battle of the First World War. Traces of trenches and mine craters can be seen on these mountains to this day.