Having achieved religious independence, Bulgarian nationalists focused on gaining political independence as well.  Two revolutionary movements started to develop in the beginning of the 1870s: the Internal Revolutionary Organisation and the Bulgarian Revolutionary Central Committee. Their armed struggle reached its peak with the April Uprising which broke out in 1876. It resulted in the Russo-Turkish War of 1877-1878, and led to the foundation of the third Bulgarian state after the Treaty of San Stefano. The treaty set up a Principality Bulgaria which territory included the wide area between the Danube and the Balkan mountain range, most of today Eastern Serbia, Northern Thrace, parts of Eastern Thrace and nearly all of Macedonia. At that time the clergy's shifts from the Orthodox to the Catholic Church and vice versa were symptomatic of the foreign powers' game that the clergy got involved after the 1878 Berlin Treaty, that partitioned the stipulated territory of the new Principality. Thus, in the interplay between the Orthodox and the Uniat doctrine, Bulgaria supported the Orthodox Exarchate. Russia supported Bulgaria. The Greek Patriarchate of Constantinople supported the Greek national idea. France and the Habsburg Empire supported the Uniats. The Ottoman Empire's attitude was depending on how it had to balance its own interests in the game with the Great Powers.. How many years did the Russo-Turkish War last?