According to the resolutions of the Berlin Congress, the Bulgarian territory, regained in the Russo-Turkish War (1877 – 1878) and recognized by the preliminary Peace Treaty of San-Stefano, is parceled out. The units of the Bulgarian Territorial Army, dislocated on the territory of Eastern Roumelia, are separated and form an independent army. According to the Constitutional Statute of Eastern Roumelia (the Constitution), the army consists of local militia (an army) and gendarmerie (police forces). In 1879 the militia of Eastern Roumelia consists of 12 battalions (7500 men in total), and the gendarmerie consists of 12 infantry and one horse companies, and one half squadron (totally 1500 men). Through the established gymnastic shooting clubs starts a mass military training of the male population in the region.
On September 6th, 1885 the troops of Plovdiv’s garrison together with the rebels’ cheta armed detachments overthrow the Roumelia’s authorities and pronounce officially the unification of Knyazhestvo (Eng. – principality of) Bulgaria and Eastern Roumelia under the sceptre of Knyaz Alexander I. The first stage of the unification of the Bulgarian people is accomplished. Enabled are opportunities for completion of the Bulgarian unification, for cultural development and economic integration with the European states. Eliminated is the avulsion of the army to one of the Knyazhestvo Bulgaria and another one of Eastern Roumelia.
Shortly after the Unification, the young Bulgarian army has to defend it by force. On November 2nd , 1885 Serbia declared war on Bulgaria. Dislocated at the Turkish borders, the Bulgarian army in three days only, by march maneuver, crosses the whole country toward the west front. The 1st and the 4th battalions of the 1st Sofia infantry regiment, in fog and rain, for 30 hours pass 86 kilometers. The population of Slivniza cheers them with “hurray”. The 8th infantry regiment coveres 95 km for 36 hours. The 5th infantry battery of 1st artillery regiment, under command of Captain Petar Tantilov, for two days and nights of nonstop march, cover 146 kilometers. European military specialists mention that the fight of Slivniza is won by the “feet of the Bulgarian soldiers”. The heroic battle of Slivniza (November 5 - 7, 1885) leads to crushing and retreat of the main forces of the Serbian Army.
After the victory of Slivnitza the Bulgarian army drives into decisive counterattack. With fierce fighting are captured Dragoman and Tsaribrod (Transl. – today Dimitrovgrad in Sebia), and then, on November 15th ,1885 Bulgarian troops seize Pirot. Only the energetic interference of Austria-Hungary forces Bulgaria to stop its whirlwind attack.
On February 19th,1886 is signed the Peace Treaty of Bucharest, which restores the peace between Serbia and Bulgaria. The victory in the campaign costs to Bulgarian people 700 casualties and 4 500 wounded. On March 24th , 1886 is concluded the Act of Top Hane, by which the Unification of Bulgaria is recognized by the Great Powers.