March 3 is Liberation Day in Bulgaria.
This day celebrates the liberation of Bulgaria from the Ottoman Empire in 1878.
Bulgaria was a part of the Ottoman Empire for more then 500 years, till 1878, when the Preliminary Treaty of San Stefano was signed between Russia and the Ottoman Empire.
This treaty ended the Russo-Turkish War (1877-1878), where Russia was the winner.
The signing of the treaty affected the other countries, that were the parts of the Ottoman Empire.
The Treaty of San Stefano provided creation of an autonomous principality of Bulgaria with the right to have a Christian government and keep its own army, thus the state functioned as independent nation.
The treaty gave Bulgarians right to elect a prince, also the Ottoman troops were to withdrawn from Bulgaria, Russian military presence was to continue for two more years.
The principality was never implemented, and the Treaty of San Stefano was suppressed by the Treaty of Berlin.