Complex sentence: After the Treaty of San Stefano, citizens of Vranje feared that the area would be conceded to the Principality of Bulgaria, and thus sent a letter to Serbian Prince Milan Obrenović with the plea not to withdraw the army from Vranje.
Split into simpler sentences: After the Treaty of San Stefano, citizens of Vranje feared that the area would be conceded to the Principality of Bulgaria. A letter was sent to Serbian Prince Milan Obrenović with the plea not to withdraw the army from Vranje.