The Battle of Cer was a military campaign fought between Austria-Hungary and Serbia in August 1914, starting three weeks into the Serbian Campaign, the initial military action of the First World War. It took place around Cer Mountain and several surrounding villages, as well as the town of Šabac. The battle was a part of the first Austro-Hungarian invasion of Serbia, began on the night of 15 August when elements of the Serbian 1st Combined Division encountered Austro-Hungarian outposts that had been established on the slopes of Cer Mountain earlier in the invasion. The clashes that followed escalated into a battle for control over several towns and villages near the mountain, especially Šabac.
De Gaulle was involved in fierce fighting from the outset As a platoon commander, He received his baptism of fire on 15 August and was among the first to be wounded, receiving a bullet in the knee at the Battle of Dinant.