The Battle of Kaymakchalan was a battle that was fought between Serbian and Bulgarian soldiers on the Macedonian Front during World War I. The battle was fought between 12 and 30 September 1916, when the Serbian army managed to capture the peak of Prophet Ilia while pushing the Bulgarians towards the town of Mariovo, where the latter formed new defensive lines. Between 26 and 30 September, the peak changed hands several times until it was decisively captured by the Serbian army on the latter date.