Battle of Kolubara

The Battle of Kolubara (3–9 December 1914) was a major victory for Serbia over the Austro-Hungarian armies during World War I. The Austro-Hungarian armies were routed, and driven back across the Serbian border.

Austrian advance
After the Battle of Drina, the Serbian army retreated to the right bank of the Kolubara River. The Serbian Army had 250,000 poorly equipped soldiers, the Austro-Hungarians had a well-equipped force of 450,000 men. On 16 November 1914, the Austro-Hungarian Balkan Army group (5th and 6th Army), commanded by General Oskar Potiorek, launched an attack across the river. Potiorek's goal was to gain control over the railroad that led from Obrenovac to Valjevo and to use it for supplying his troops instead of using muddy roads in Mačva. The 5th Army, which held the northern part of the front, captured the town of Lazarevac which was held by the Serbian 2nd Army. In the south, the 15th and 16th Corps of the 6th Army attacked the 1st Serbian Army, captured Mount Maljen on 24 November, and put the Serbian left wing in a difficult situation. On 25 November, the Austro-Hungarian 5th Army pushed back the 2nd and 3rd Armies, crossed the Ljig River and out-flanked the 1st Army.

Because the Serbian First Army was in a difficult situation, its general, Živojin Mišić, wanted to abandon his current positions and retreat to a new position in front of the town of Gornji Milanovac. His plan was to delay combat, rest his troops, and then launch a counteroffensive. Radomir Putnik, the Chief of the Serbian General Staff, did not approve of the plan. He warned Mišić that in that case other armies would also have to retreat, and Belgrade would have to be abandoned. Mišić told Putnik that the orders had already been given, and that he would not change them while he was in command. In the end, Putnik accepted the plan.



When Belgrade was abandoned, Potiorek made a new plan. He wanted to amass the entire 5th Army in the Belgrade region to annihilate the Second Army, which was on the right wing of the Serbian front. The 5th Army would then turn to the south, get behind the Serbs, and force them to capitulate. Potiorek underestimated the offensive capabilities of Mišić's First Army in the south. He thought that they were too tired and weakened to do more than hold while his forces were maneuvering.

The Austro-Hungarian soldiers were very tired even before this maneuver began. While they were marching, Serbian troops were resting in their new positions. On 2 December, Mišić finished all preparations for an attack. Putnik ordered the offensive to begin, using the entire Serbian army on 3 December. That was an ideal moment, because the largest Austro-Hungarian formation, the Combined Corps, was by then out of combat, marching north.

Serbian counterattack
On 3 December, the First Army launched an attack against the surprised 16th Corps. The attack was supported by the Užice army from the left wing. 16th Corps suffered heavy casualties and was pushed back. On 4 December, 17th Corps tried to hold the advance of the 1st Army, but failed. Potiorek ordered an attack by the 5th Army so that he could complete his operation before the 6th army was defeated. However, the Combined Corps was still on its march.

On 5 December, the First Serbian Army captured Mount Suvobor 44.1237°N, 20.1759°W, the main defensive position of the 6th Austrian Army. Meanwhile, the Third Serbian Army had failed to push 15th Corps off Mount Rudnik, the Užice army suffered heavy casualties. However, these formations pressured the Austro-Hungarian forces and helped the First Serbian Army to achieve a breakthrough. In the evening, the Combined Corps arrived at its new position with very tired soldiers.

On 6 December, Potiorek ordered the retreat of the 6th Army on the left bank of the Kolubara. Combined Corps finally attacked the Second Army, but the attack was easily stopped. The Combined Corps launched a major attack on 8 December, but the Second Serbian Army managed to hold its position. Other units of the 5th Army under General Liborius Ritter von Frank were more successful, but it was too late. The First Serbian Army had captured Valjevo and was pushing north. Vojvoda Putnik reinforced the Second Serbian Army with fresh troops and ordered an attack before the Austro-Hungarians could fortify their positions. On 12 December, Stepanović's 2nd Serbian Army attacked and defeated the 8th Corps. The 5th Army had to leave Belgrade and cross the Sava River on 15 December.

The Serbian Army captured 76,000 enemy soldiers; the number of Austro-Hungarian casualties was even greater. The invading army abandoned large quantities of military equipment, according to some sources enough "to equip three army corps". Mišić was promoted to Vojvoda, while Potiorek was retired, replaced by Archduke Eugen of Austria who was placed both in command of the 5th army and as commander-in-chief of the Balkan army group from December 1914.

In 1914 the Austro-Hungarian Balkan Army Group lost around 224,500 men (out of a total of 450,000 engaged in the battle), while the Serbian army lost around 170,000 men (nearly its entire pre-war strength).

Results
Austria had taken massive losses and yet failed to conquer or defeat Serbia. The Austro-Hungarian 5th and 6th Armies were driven out of Serbian territory, abandoning Belgrade to the Serbs. Meanwhile, it was under intense pressure from the Russian army on its eastern frontier.

In a very unusual act, German emperor Wilhelm II personally congratulated Radomir Putnik on the victory.

Since Serbia did not really pose a threat to Austria, the Austrians did nothing against Serbia for the next 10 months; most of the forces in the area were transferred to the Italian front. On the other hand, although victorious, Serbian losses were even larger as a proportion of their army strength. Coupled with a typhus epidemic that raged through the countryside during the winter, Serbia remained on the defensive in 1915, hoping for increased Allied support which never came.