A map of the Principality of Bulgaria and Eastern Rumelia before the Unification.
The Unification of Bulgaria (Bulgarian: Съединение на България, Saedinenie na Balgariya) was the act of unification of the Principality of Bulgaria and the then-Ottoman province of Eastern Rumelia in the autumn of 1885. It was co-ordinated by the Bulgarian Secret Central Revolutionary Committee (BSCRC). The Unification was accomplished after revolts in Eastern Rumelian towns, followed by a coup on September 6, 1885 supported by the Bulgarian Knyaz Alexander I.
The Unification was initially scheduled for the middle of September, while the Rumelian militia was mobilized for performing manoeuvres. The plan called for the Unification to be announced on September 15 1885, but on September 2 a riot began in Panagyurishte (then in Eastern Rumelia) that was brought under control the same day by the police. The demonstration demanded Unification with Bulgaria. A little later this example was followed in the village of Goliamo Konare. An armed squad was formed there, under the leadership of Prodan Tishkov (mostly known as Chardafon) — the local leader of the BSCRC. BSCRC representatives were sent to different towns in the province, where they had to gather groups of rebels and send them to Plovdiv, the capital of Eastern Rumelia, where they were under the command of Major Danail Nikolaev.
Telegram from the provisional government in Plovdiv to Knyaz Alexander I proclaiming the Unification of Bulgaria
Meanwhile, military manoeuvres were being carried out in the outskirts of Plovdiv. Mj. Danail Nikolaev, who was in charge of the manoeuvres, was aware of and supported the unionists. On 6 September, Rumelian militia (Eastern Rumelia's armed forces) and armed unionist groups entered Plovdiv and took over the Governor's residence. The Governor was Gavrail Krastevich, a Bulgarian patriot who, naturally, did not resist the unionists.
A temporary government was formed immediately, with Georgi Stranski at its head. Major Danail Nikolaev was appointed commander of armed forces. With help from Russian officers, he created the strategical plan for defence against the expected Ottoman intervention. Mobilization was declared in Eastern Rumelia.
As soon as it took power on September 2, the temporary government sent a telegram, asking the knyaz to accept the Unification. On September 8 Alexander I answered with a special manifest. On the next day, accompanied by the prime minister Petko Karavelov and the head of Parliament Stefan Stambolov, Knyaz Alexander I entered the capital of the former Eastern Rumelia. This gesture confirmed the unionists' actions as a fait accompli. But the difficulties of the diplomatic and military defence of the Union lay ahead.
In the years after the signing of the Berlin Treaty, the St. Petersburg government had often expressed its view that the creation of Eastern Rumelia out of Southern Bulgaria was an unnatural division and would be short-lived. Russia knew that the Unification would undoubtedly come soon and took important measures for its preparation. First, Russia exerted successful diplomatic pressure upon the Ottoman Empire constraining it from sending forces into Eastern Rumelia. Also, in 1881, in a special protocol, created after the re-establishment of the League of the Three Emperors, it was noted that Austria-Hungary and Germany would show support for a possible union act of the Bulgarians.