The Austro-Hungarians have twice tried to invade Serbia, each time suffering terrible defeats. Now they are having another go, again under the command of General Potiorek. Potiorek is determined that this time there will be no mistakes. He has assembled a vast force that outnumbers the Serbs two-to-one. And his force is well equipped, unlike the Serbs who are already starting to run out of war materiel. The Serbian army is unable to hold off the invasion and is obliged to retreat.
image source (Wikipedia)