It is one of the ironies of the First World War that the conflict began with the tensions between Austria-Hungary and Serbia, but that the bitter fighting in the trenches of the Western Front should eclipse everything else, while the Austrian invasion of Serbia would largely be forgotten. The campaigns were fought over the course of a year and a half, but about half of that time was spent in relative quiet due to manpower and supply shortages on both sides. In 1914, the Austrians made two invasions of Serbia, both of which were repulsed; in 1915, the Austrians returned with support from Germany and Bulgaria, eventually placing Serbia under occupation and driving the remnants of the Serbian Army into exile.
On paper, Austria-Hungary’s greater size offered it a substantial advantage over Serbia when it declared war. It regular army would number 1.3 million after the reserves were summoned, with an additional million in the Landsturm reserve. While the Imperial and Royal Army only numbered some 450,000 active service personnel at the beginning of the crisis, its commanders considered its numbers large enough to defeat Serbia, which mustered only 360,000 men after mobilizing for war. The Austrians expected an easy victory.
Several errors hid within this logic. The first did not escape the eye of Austrian planners: Austria would not be free to fight Serbia at its leisure. The Dual Monarchy would face two threats, the Serbs in the south and the Russians in the east. Given the threat posed by the Russians, even with the rosiest assumptions about German help, the Austrians could afford to detach only three armies from their main body to carry out the invasion of Serbia. When Russian mobilization proved much more rapid than anyone had anticipated, this required the transfer of additional units to the east. While Fifth and Sixth Armies remained in the operation, Second Army was reduced to just two corps, with the remainder being pulled to the east.
This would be troublesome enough for any realistic commander, but the Austrians failed to assess their opponents in qualitative terms. The war had caught the Serbs in the midst of a military modernization drive; the incomplete nature of these preparations ensured that the Serbian Army would have inadequate stockpiles of weapons and ammunition, especially artillery ammunition. This fact did not serve to offer the Austrians any great advantage, however, as the same could be said of the Imperial and Royal Army. Linguistically and culturally, the Serbian Army was much more cohesive than the multinational Imperial and Royal Army, and just as importantly, it was a more experienced force. Serbia and fought in two previous Balkan wars in 1912 and 1913, and the core of its military could draw upon this experience, offering the Serbs certain advantages even after the ranks were filled with fresh recruits.
Finally, the Serbs were vastly more fortunate in their supreme commander than the Austrians. The Serbs were led by the wily General Radomir Putnik, who as Chief of Staff had been busy with the modernization of the Serbian Army when the war began. The Austrian forces in the Serbian theater of war boasted General Oskar Potiorek, instead; significantly, he was the same man who had coordinated security in Sarajevo on the day that the Archduke Franz Ferdinand had been assassinated. His performance in war would remain consistent.
Austria’s declaration of war was delivered by telegraph on July 28. On the 29th, active hostilities began Austrian gunboats shelling the Serbian capital, Belgrade, from the river Danube. For two weeks, this was the limit of the fighting while both sides arranged their forces. The Austrians massed their three armies to the north and west of Serbia, while the Serbs held theirs in reserve in the northern half of the country, ready to respond to any of several threats.
The slow pace of the Austrian attack, when it came on August 12, allowed the Serbs to concentrate their forces in response to the threat. Regardless of the point of insertion, the Austrians needed to cross one or both of the rivers Sava and Drina. Potiorek decided not to cross the river Sava too near the Serbian capital, and so he was left with a western crossing over the Drina, with supplemental forces crossing the Sava where the two rivers meet. When Putnik realized that no additional forces would cross the Sava further east, he was free to bring his entire force together to meet the Austrians.
First contact between the two sides was on August 16, and from that date events transpired very quickly. In what became known as the Battle of Jadar River, the Serbs struck at both flanks of the Austrian advance, halting it by the 19th and pushing it back to the Drina by the 21st. Austrian flight had left the Serbs in possession of useful supplies. A combination of factors led the Serbs to a dangerous overextension of their forces, however. On the one hand, the western Allies urged the Serbs to follow up their victory with an invasion of Austrian territory, while on the other, a belief in their own superiority over the Austrians and a faith in the common cause of the Slavs under Austrian domination inspired the Serbs to undertake their own crusade in Austrian lands, trusting in their fellow Slavs to rally at once to the movement.
The effort produced no such results, and the Serbs were compelled to abandon it when Potiorek led a second crossing of the Drina on September 7. Their hand forced, the Serbs threw themselves at the invasion, but this time, in the Battle of the River Drina, they failed to dislodge the Austrians. On September 17, the Serbs withdrew and regrouped at the river Kolubara, temporarily leaving Belgrade vulnerable. For their part, the Austrians consolidated their positions until the beginning of November, when they opened a third offensive.
The third offensive seemed at first to be highly successful, driving the Serbs further south and permitting the Austrians to capture Belgrade on December 2. Putnik, however, was only buying time until fresh supplies from France could arrive, while Austrian forces gradually outpaced their own supply column. On December 3, Putnik launched an attack of his own, and in six days he again drove Austrian forces from Serbian territory. The Austrians had lost 227,000 men in the Serbian campaigns, a little more than half of the force that had begun them in August. Serbian losses were high, too, at 170,000, and typhus would prove devastating during the winter that followed. Neither side was in a hurry to return to battle in 1915.
Strategic considerations changed the role of Serbia in 1915. As Rumania began to distance itself from the Central Powers, Germany worried about its rail connection with Turkey. The alternative route was a train that passed near Belgrade and followed the river Morava before turning east at Nish, moving on to Turkey through Bulgaria. For the Germans, the securing of Serbia then assumed a vital importance, and with that change, Austrian control over their own sector of the war ended. When Bulgaria formally allied itself with the Central Powers on September 6, it became possible for the Germans to arrange a large and systematic offensive that was capable of defeating Putnik. Command of this operation was placed in the hands of one of Germany’s most effective Generals, August von Mackensen.
Germany and Austria began the new offensive on October 6, with the Austrian Third Army and the German Eleventh Army striking across the Sava and Danube rivers at the Serbian First and Third armies, respectively. The Germans captured Belgrade on the 9th, and then on the 11th, the Bulgarians opened their participation with an invasion from the east by two more armies, the First and Second. For his part, Putnik struggled to maintain a fighting retreat, hoping to buy time for an Allied intervention on his behalf, but this never happened.
Instead, the “Great Retreat” led the last vestiges of the Serbian Army out of Serbia and into the mountains of Montenegro and Albania. There, they came under attack by many local villages, and after losses due to all causes, only 150,000 men survived to be rescued by Allied navies. They were sent at first to Corfu, where starvation further winnowed down the Serbs. Eventually, 85,000 survived to be relocated to Salonika, where they served until the end of the war. Putnik, who suffered from asthma, was sent to France, where he died in 1917.
For their part, the Austrians followed up with the occupation of Montenegro, but this did little to secure their flank. 1915 saw the decision of Italy to enter the war on the side of the western Allies, while 1916 brought a Rumanian declaration of war and a fairly successful Russian offensive. Only with German oversight and regular intervention were the Austrians able to stave off their own collapse until 1918.
Sources:
Forty, Simon. World War I: A Visual Encyclopedia. PRC Publishing, 2002
Griess, Thomas E. The Great War: Strategies & Tactics of the First World War. West Point Military History Series, 2003
Livesey, Anthony. The Historical Atlas of World War I. Henry Holt, 1994
Neiberg, Michael S. et al. The History of World War I: The Eastern Front 1914-1920. Amber, 2012
Strachan, Hew. The Oxford Illustrated History of the First World War. Oxford, 2001
Westwell, Ian. The Complete Illustrated History of World War I. Anness Publishing, Ltd., 2008
Willmott, H.P. World War I. Covent Garden Books, 2003
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