In 1885, Eastern Rumelia, an autonomous province established by the Treaty of Berlin in 1878, declared its unification with Bulgaria. Following the turbulent period of national awakenings and efforts toward independence from Ottoman rule, the desire for unification became increasingly pronounced among Bulgarians. The annexation was led by a popular movement characterized by widespread support from Bulgarian nationalists and the public. The local administration in Eastern Rumelia, under Governor Georgi Zhivkov, had to navigate a political landscape fraught with pressure from both the Ottoman Empire and domestic factions. The proclamation was declared in Plovdiv, gaining immediate support and legitimizing the national aspirations of the Bulgarian people.

The successful unification of Eastern Rumelia with Bulgaria not only strengthened the Bulgarian state but also stirred nationalist sentiments across the Balkan region. The union highlighted the growth of Bulgarian national consciousness and the peoples' desire for a singular Bulgarian state, free from foreign dominance. The event sparked a series of diplomatic tensions, leading to a brief military conflict known as the Serbo-Bulgarian War, where Serbia sought to oppose Bulgaria's growing influence.