Why did the Second Balkan War begin in 1913?

The Second Balkan War began in 1913 due to an irreconcilable dispute among the former allies of the Balkan League—Bulgaria, Serbia, and Greece—regarding the partitioning of Macedonia following their victory over the Ottoman Empire in the First Balkan War.12

While the allies had successfully driven the Ottomans from most of their European territories, they had failed to resolve competing territorial claims before the conflict began. Following the Treaty of London in May 1913, Serbia and Greece insisted on retaining the Macedonian lands they had occupied, while Romania also demanded compensation for its neutrality.234

Bulgarian leadership, particularly King Ferdinand, favored a military solution to these diplomatic failures. The war officially commenced on the night of June 29–30, 1913, when Bulgarian forces launched a surprise attack on Serbian and Greek positions in Macedonia. This aggression ultimately led to a broader conflict involving Romania and the Ottoman Empire, resulting in a decisive defeat for Bulgaria.241