A few years after Bulgaria's liberation in 1878, Bulgarian nationalists organised a coup in the Ottoman province of Eastern Rumelia and declared its unification with the Principality of Bulgaria. The Kingdom of Serbia opposed the strengthening of its rival. Serbian king Milan I declared war on Bulgaria on 14 November 1885, but the Serbian forces were decisively defeated at the Battle of Slivnitsa between 17 and 19 November. Another decisive Bulgarian victory occurred at Gurgulyat, where Bulgarian soldiers and civilian volunteers fought the Serb Moravian division and prevented it from reinforcing the main Serbian force at Slivnitsa.