Cause:
The Treaty of Berlin of 1878 left abundant material for future conflict in European Turkey. Bulgaria was confined to the north of the Balkan mountains, and Eastern Roumelia was still under the Sultan. Prince Alexander of Battenberg, the ruler of Bulgaria, in September 1885, marched south and occupied Philippopolis. The Sultan protested, the Czar was indignant, but Great Britain approved the Union of Roumelia with Bulgaria, and the danger of war passed away. The success of Bulgaria whetted the appetite of Milan, who had become King of Serbia in 1882. With a view to strengthening the prestige of his dynasty he adopted a spirited foreign policy and awaited an opportunity.