The Serbo-Bulgarian War or the Serbian–Bulgarian War (, Srăbsko-bălgarska voyna, , Srpsko-bugarski rat) was a war between the Kingdom of Serbia and Principality of Bulgaria that erupted on and lasted until . Despite Bulgaria being a vassal state of the Ottoman Empire, the Turks did not intervene in the war. Serbia took the initiative in starting the war but was decisively defeated. Austria demanded Bulgaria stop its invasion, and a truce resulted. Final peace was signed on in Bucharest. The old boundaries were not changed. As a result of the war, European powers acknowledged the act of Unification of Bulgaria which happened on . Background On , Bulgaria and the semi-autonomous Ottoman province of Eastern Rumelia declared their unification in the city of Plovdiv. Eastern Rumelia, whose population was predominantly ethnic Bulgarian, had been an artificial creation of the Berlin Congress seven years earlier. The unification took place against the will of the Great Powers, including Russia. Austria-Hungary had been expanding its influence in the Balkans and was particularly opposed to the unification. Bulgaria's western neighbour, Serbia, also feared it would diminish its position in the Balkans. In addition, Serbia's ruler, Milan I (1868–1889), was annoyed that pro-Russian opposition leaders like Nikola Pašić, who had stirred up the Timok Rebellion, had found asylum in Bulgaria after the suppression of the rebellion by the Serbian Army. After the declaration of unification, massive protests broke out in Greece for fear of the creation of a Greater Bulgarian state in the Balkans. They called upon the Greek government to declare war on Bulgaria. Serbia proposed to Greece a joint military action against Bulgaria, but Greece rejected the proposal. Lured by Austria-Hungary's promises of support and territorial gains from Bulgaria (in return for concessions in the Western Balkans), Milan I declared war on Bulgaria on . The military strategy relied largely on surprise, as Bulgaria expected an attack from the Ottoman Empire and had moved its troops to the area near the Turkish border, to the southeast. The Serbian pretext was a minor border dispute, known as the Bregovo Dispute. The Timok River, which formed part of the border between the two countries, had slightly changed its course over the years. As a result, a Serbian border guardhouse near the village of Bregovo had found itself on the Bulgarian bank of the river. After some denied requests from Bulgaria to evacuate the guardhouse, Bulgaria