三帝同盟
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.