As war began, the. Austrians were optimistic. Their troops were fresh for battle, but those ol Serbia were already dog-eared from two recent Balkan campaigns. Austrian equipment was also superior. On the other hand, Serbian morale was also high as the tiny nation steeled itself to defend its hearths.
On 1 1 .August the Austrian. Second. Army crossed the Sava riser and easily took the town of Jsabac. But next morning, as the Fifth. Army crossed the Drina, it encountered heavy fire from two Serbian disisions. .cxt day, Serbian harassment from high defensise positions brought the Austrian olfensisc to a temporary halt, but it sub-sc(|uently moved forward, sustaining enormous losses.
The. Austrians were led by Potiorek, the mis-manager of the arc hducal visit to Sarajevo. On icj. August, after Serbians under Putnik launched a counteroffensive, Potiorek unsteadily withdrew his forces back across the Drina, and by the twenty-fourth the Austrians had completely evacuated Serbia.
On 7 September, Potiorek was able to cross back into Serbian territory. 'Fhis time he inflicted severe casualties on the enemy. In one horrendous disaster, a Serbian division, which had entered Hungary, was trapped as it tried to recross into Serbia. Five thousand men were mown down in a few hours. Een so, Putnik managed a counterthrust at Sarajevo, causing Potiorek to pursue him for seven weeks in an effort to ensure the safety of the Bosnian capital.
By 25 October Bosnia had been cleared of Serbian forces, and Austrian predominance in men and supplies had had its effect. Vet as Potiorek dro e back the enemy, his pursuit was so relentless that it reduced his own forces to physical and spiritual wrecks. Somehow he managed to take the offensive again in the first week of November, and his task was helped by the heavy rain and ice which ])layed havoc with the Serbian supply lines. On 2 December, by a happy coincidence the sixty-sixth anniversary of the accession of Franz Josef, Belgrade was captured. .Austria now became overconfident. Fhough Serbia was practically destitute of reserves of ammunition, the courage of her men endured. Next day, 3 December, the Serbs threw themselves with suicidal abandon at the Austrians and the. Austrian lines caved in. By 13 December, Potiorek was once more driven back across the .Sava; Belgrade w:is relieved on 15 December.
.Austria had sustained over one hundred thousand casualties; in addition, her troops had abandoned countless weapons which were invaluable to the Serbs. Yet Serbia was unable to jmess forward her advantage. The oncoming winter, the ravages of typhus, and the loss of more than half of her crack troops fincluding one hundred and seventy thousand dead and injured) produced a stalemate which was to last for many months.