The Treaty of San Stephano that ended the Russo-Turkish War of 1877–8 created a Great Bulgaria that stretched far into the west of Ottoman Europe. The Russians, who had created the new country and whose troops remained in occupation, wanted a pliant Bulgaria, in effect a client state. Others opposed the Russian plan: Austria feared any Russian aggrandizement in the Balkans. A Bulgaria whose borders extended from the Black Sea to Albania would also stand in the way of Austrian hopes for their own expansion in the Balkans. The other Balkan nations – Serbia, Romania and Greece – opposed and feared the creation of a Greater Bulgaria. Britain opposed an extension of Russian influence and power that might ultimately lead to Russian control of the Straits.

Reducing the large Bulgaria created in the Treaty of San Stephano, at the Congress of Berlin the Powers created two Bulgarias – an independent Bulgaria, in theory a tributary of the Ottoman Empire, and an autonomous Eastern Rumelia. Eastern Rumelia was theoretically a province of the Ottoman Empire, but with its own Christian governor and a native militia and gendarmerie, although Ottoman forces still defended the border with Bulgaria. In population, Eastern Rumelia was just as Bulgarian as was the Kingdom of Bulgaria – slightly less than 75 per cent. Bulgarians were left with two irredentist goals – unity of Eastern Rumelia with Bulgaria and taking the rest of what they had been awarded in the Treaty of San Stephano.

In 1885 a rebellion in favour of uniting Eastern Rumelia with Bulgaria broke out in Plovdiv and spread rapidly. Prince Alexander of Bulgaria, fearing that to do otherwise would cost him his throne, supported the rebels. Under the terms of the Berlin Treaty, the military border of the Empire was on the prime defensive position of the Balkan Mountains. Losing it would leave the Empire less protected from attack from the North. The Ottomans prepared for war, but the Powers stepped in and forced them to stand down. Most of the Powers, particularly Russia, opposed any Bulgarian unification that upset the terms of the Treaty of Berlin.