Bulgaria became part of the Ottoman Empire in 1396. In April 1876, there was a series of uprisings against Ottoman rule in Bulgaria. 

The harsh suppression of the revolts by the Ottomans led to widespread international condemnation and in April 1877, Russia formally declared war on the Ottoman Empire. The war ended in March 1878 with the signing of the San Stefano peace treaty. The other leading nations at the time felt that the peace treaty created a Bulgaria, that was too large and would have too much influence on the region. As a result, under the Treaty of Berlin in 1878, Southern Bulgaria (Eastern Rumelia) was separated from the Principality of Bulgaria and returned to the Ottoman Empire, with partial autonomy. 

Bulgarians felt that the decision of the Berlin Treaty was unfair. Over the following seven years, initially peaceful demonstrations gave way to rebellion and conflict. The Bulgarian Secret Central Revolutionary Committee was formed in February 1885, which organised events and revolts in towns in Eastern Rumelia, designed to assist in the unification process. On September 6th 1885, Bulgaria and Eastern Rumelia declared their unification in the city of Plovdiv. 

The unification angered several powerful nations and led to the Serbo-Bulgarian War. Bulgaria emerged as victors from that conflict and established acceptance of their borders.