In Bulgarian historiography, the term Liberation of Bulgaria is used to denote the events of the Russo-Turkish War of 1877-78 that led to the re-establishment of Bulgarian state with the Treaty of San Stefano of 3 March 1878, after the complete conquest of the Second Bulgarian Empire, which finished in 1396. According to this treaty, the Ottoman Empire was deprived of a big part of its territory, which were given to the client state - Bulgaria.
In the same year, at Berlin congress, Treaty of Berlin (1878) was adopted, according to which, the territories of the Bulgarian state, created as of San Stefano's treaty were divided into three parts: the first part was the Principality of Bulgaria which functioned independently but nominally within the Ottoman Empire, this was limited to Moesia and neighbouring areas of the capital Sofia; the second part created was to be an autonomous province of the Ottoman Empire - Eastern Rumelia; the third and the largest part - Macedonia and Lozengrad were given back to the Ottoman Empire, also some outlands were given to Serbia and Romania. The seized territories from Bulgaria after Berlin congress - most of Macedonia, Thrace, etc. were with an ethnic Bulgarian majority. On September 6, 1885, Eastern Rumelia became part of Princiapality of Bulgaria after a bloodless unification, though still de jure within the Ottoman Empire.
The third Bulgarian state gained full sovereignty from the Ottoman Empire on 22 September 1908 when declaring independence.
The term is, however, partially inaccurate, as it only refers to the liberation of Bulgaria from Ottoman rule, the second liberation of Bulgaria. After the conquest of the First Bulgarian Empire in 1018, the first liberation of Bulgaria, led to the establishment of the Second Bulgarian Empire, happened in the year 1185 as a consequence of the Uprising of Asen and Peter against the Byzantine Empire.