In Eastern Europe, the First World War began with the Austro-Hungarian invasion of Serbia on August 12, 1914. The two sides clashed at Cer Mountain on the night of August 15–16, 1914. By the next day, the Austro-Hungarians had retreated from the mountain. Beginning on the 17th, the Serbs attempted to take the nearby town of Sabac. They were repulsed on the 17th and 18th, but succeeded on the 19th and also took the village of Rasulijaca, after which the Austro-Hungarian army began retreating in disorder from Serbia.