Bulgaria was the site of much of the fighting during the Russo-Turkish War 1877-8, and revolted again against Turkish control. Following intervention by Russia, a principality was established north of the Balkan mountains in 1878. This was confirmed by the Treaty of Berlin in the same year. The area south of the new territory, Eastern Rumelia, was granted a semi-autonomous administration, both regions remaining under Turkish suzerainty.

Postal service under direct Turkish control in both areas was well developed and at least 16 POs were in operation.

In 1880 Eastern Rumelia issued its own stamps overprinted on Turkish stamps. In 1885 there was a popular revolt in Rumelia in favour of union with Bulgaria and the name of the province was changed to Southern Bulgaria. This province then issued its own stamps from 10 September 1885 until Bulgarian stamps were introduced throughout the area from 1 October in the same year.

Bulgaria remained a principality under Turkey until it became an independent kingdom in 1908. Bulgaria supported the other Christian states, Serbia, Montenegro and Greece, in the first Balkan War in 1912. Bulgaria was keen to extend its boundary to the south into Thrace and to obtain a port on the northern Aegean Coast.

Britain and Germany restrained their allies to prevent a full-scale European war. Bulgaria was the most successful of the countries in the war and obtained much additional territory. However, an armistice was signed on 3 December 1912 and the London Peace Conference broke down because of the Bulgarian insistence that it should obtain Adrianople in Turkish Thrace. This could not be agreed and Bulgaria, underestimating the strength of the opposition, renewed the fighting.

However, in face of attacks from Serbia and Greece, supported by Romania, who had held aloof from the first Balkan War, Bulgaria was defeated and the second Balkan War was concluded by the Treaty of Bucharest on 10 August 1913. By this, Bulgaria gained western Thrace and access to the Aegean.

1914-18
On 6 October 1915, after the British repulse at Gallipoli, Bulgaria entered the war on the side of the Central Powers and took part in the defeat of Serbia on the western border and Romania on the northern border. It acted in support of its Turkish allies in eastern Thrace and, after the defeat of Serbia, acted as the holding force in the Salonica area. The stalemate was broken in 1918 and Bulgaria was defeated by the Allies, who advanced through their territory into Romania and Russia. Bulgaria lost eastern Thrace to Greece and has remained largely within the same boundaries ever since.

1918-39
A kingdom under Boris III, Bulgaria continued to develop a new national identity between the wars. The creation of the new Yugoslavia effectively contained the eastern frontier and after some fighting with Greece on the southern boundary in 1925-6, a period of comparative peace followed.

1939-45
World War II did not affect the Balkans immediately. However, the attack on Greece by Italy in October 1940 led to the need for German assistance in the area. German control was consolidated by forcing Bulgaria to join the Axis on 1 March 1941. German troops passed through Bulgaria to attack Greece on 6 April and Greece surrendered on 27 April.

As part of the Anglo-Russian discussions in 1944, Russian dominance in the Balkans and particularly Bulgaria was acknowledged. The advance from Russia into the Balkans led to the capture of Sofia on 5 September 1944. Stamps of the kingdom of Bulgaria continued in use during the war.

1945 to date
As the result of a referendum, the king was deposed on 15 September 1946 and a People's Republic was declared on the same day. Stamps of the new regime replaced the previous royal issues.

The Bulgarian Communist Party (BCP) dominated the post-war scene. After their leader, Todor Zhikov, was forced to resign in November 1989, further leadership changes culminated in the National Assembly voting to abolish the BCP's constitutional guarantee of power in January 1990. Later the same year, multi-party elections were held and a new constitution was prepared.

In 1994, the BSP briefly regained power, but was forced to resign because of the falling standard of living.