The concept of a Balkan federation emerged at the late 19th century from among left political forces in the region. The central aim was to establish a new political unity: a common federal republic unifying the Balkan Peninsula on the basis of internationalism, socialism, social solidarity, and economic equality. The underlying vision was that despite differences among the Balkan peoples the historical need for emancipation was a common basis for unification.
This political concept went through three phases in its development. In the first phase the idea was articulated as a response to the collapse of the Ottoman Empire at the beginning of the 20th century. In the second phase, mostly through the interwar period (1919–36), the idea of the Balkan federation was taken up by the Balkan communist parties. The third phase is characterized by clash between Balkan communist leaders and Joseph Stalin as an opponent of the idea during the post-World War II period.
At first, in Belgrade in 1865 a number of radical Balkan intellectuals founded the Democratic Oriental Federation, proposing a federation from Alps to Cyprus based on political freedom and social equality. They confirmed their adherence to the ideals of French Revolution in the line of Saint-Simon’s federalism and in relation to the socialist ideas of Karl Marx or Mikhail Bakunin. Later, in France, a League for the Balkan Confederation, was constituted in 1894, in which participated Greek, Bulgarian, Serbian and Romanian socialists, supporting Macedonian autonomy inside the general federation of Southeast Europe, apprehending the complexity of the Macedonian Question. The next attempt came immediately after the Young Turk Revolution in 1908. The following year, in Salonika the Socialist Workers Association merged with two Bulgarian socialist groups and the Socialist Worker’s Federation of Ottoman Workers was founded. Although it underestimated, till 1913, the political significance of the national question, as this significance manifested itself in the right of national self-determination, and its leadership kept a moderate position in regard with the nationalistic tendencies in Balkan social-democratic parties.
Balkan Socialist Federation
On January 7 and 9, 1910, the First Balkan Socialist Conference was held in Belgrade, then within the Kingdom of Serbia. The main platforms at the first conference were Balkan unity and action against the impending wars. Another important aspect was the call for a solution to the Macedonian Question. In 1915, after a Conference in Bucharest; it was decided to create a Revolutionary Balkan Social Democratic Labour Federation, comprising groups who adhered to the Zimmerwald Conference and opposed participation in World War I. Initially headed by Christian Rakovsky, it had Vasil Kolarov and Georgi Dimitrov among its prominent activists. In 1915, Dimitrov wrote that Macedonia, "...which was split into three parts...", would be, "...reunited into a single state enjoying equal rights within the framework of the Balkan Democratic Federation."  This independent and united Macedonia would have consisted of the corresponding geographical departments of Bulgaria, Yugoslavia and Greece. The Federation was repressed by national governments at different intervals (Rakovsky himself was arrested by the Romanian government in 1916).
Balkan Communist Federation
After the October Revolution in Russia, a Balkan Communist Federation was formed in 1920–1921, and was influenced by Vladimir Lenin's views on nationality (see Proletarian internationalism). It was a communist umbrella organisation in which all the communist parties in the Balkans were represented. It was dominated by the Soviet Union and Comintern requirements. It advocated a "Balkan Federative Republic" that would have included Bulgaria, Yugoslavia, Greece, and Turkey; some projects also involved Romania, but most of them only envisaged its fragmentation. The body thus oversaw the activities of the Bulgarian Communist Party (BKP), the Communist Party of Yugoslavia (KPJ), the Communist Party of Greece (KKE), the Communist Party of Turkey (TKP), and, to a certain measure, those of the Communist Party of Romania (PCdR). It was disestablished in 1939.
From the beginning, the Bulgarians assumed a leading role in the BCF. In Sofia, May–June 1922, the question of the "autonomy of Macedonia, Dobruja and Thrace was raised by Vasil Kolarov and was backed by Dimitrov, the Bulgarian delegate who presided over the meeting. The Greek delegate asked for a postponement as he was reluctant to approve a motion that was not on the agenda. In December 1923, Balkan Communist Federation held its 5th Conference in Moscow. In 1924 the Comintern entered negotiations about collaboration between the communists and the Internal Macedonian Revolutionary Organization (IMRO), Internal Thracian Revolutionary Organisation (ITRO) and Internal Dobrujan Revolutionary Organisation (IDRO) and the creation of a united revolutionary movements. The idea for a new unified organizations was supported by the Soviet Union, which saw a chance for using this well developed revolutionary movements to spread revolution in the Balkans and destabilize the Balkan monarchies. The so-called May Manifesto of 6 May 1924 was issued in which the objectives of the unified Macedonian liberation movement were presented: independence and unification of partitioned Macedonia, fighting all the neighbouring Balkan monarchies, forming a Balkan Communist Federation and cooperation with the Soviet Union. In 1925, a left wings named Internal Macedonian Revolutionary Organization (United), Dobrujan Revolutionary Organisation and Internal Thracian Organization, respectively, seceded from the main organizations under the influence of the Bulgarian Communist Party. This wings militated for a Soviet Republics, which would either be part of a "Balkan Communist Federation". The Bulgarian Communist Party was compelled by Joseph Stalin to accept the formation of Macedonian, Thracian and Dobrujan nations in order to include those new separate states in the Balkan Communist Federation. Later even a resolution of the Balkan Communist Federation for the recognition of a Macedonian ethnicity was issued on January 7, 1934, by the Balkan Secretariat of the Comintern. It was accepted by the Political Secretariat in Moscow on January 11, 1934, and approved by the Executive Committee of the Comintern.
The Communist Party of Greece (KKE) delegate Nikolaos Sargologos signed the motion without central authorisation; instead of returning to Athens, he emigrated to the United States. The KKE political organ and newspaper, Rizospastis, was against the motion because it saw it as good for BCP in Bulgaria but disastrous for the KKE in Greece. The KKE found the BCF's position on Macedonia difficult but briefly went along with it. In June 1924, at its 5th meeting, it recognised "the Macedonian people" and in December 1924, it endorsed the motion for "a united and independent Macedonia and a united and independent Thrace" with the perspective of entering into a union within a Balkan federation "against the national and social yoke of the Greek and Bulgarian bourgeoisie". However, in 1928 it suffered a crushing defeat at the Greek elections, especially in Greek Macedonia. By 1927, dissentions within the KKE made the motion untenable and in March, the KKE conference watered it down, calling for autodetermination of the Macedonians until they join a "Balkan Soviet Socialist Federation" and only for "a section of Macedonia (Florina area) inhabited by Slavomacedonians" (Holevas 1992). By 1935, it simply called for "equal rights to all" due to the "change of the national composition of the Greek part of Macedonia" and hence because "the Leninist–Stalinist principle of self-determination demands the substitution of the old slogan". The Communist Party of Yugoslavia (YCP) had its own problems and dissentions; fears of Serbianisation of the party and of the Vardar Banovina, whose inhabitants felt closer (though not necessarily identified) to Bulgaria than the Kingdom of Yugoslavia. The YCP followed the KKE example in 1936.
In 1936 the left wings of IMRO, ITRO and IDRO were incorporated by regional principle into the Balkan Communist Parties.
Period after Comintern (1943–)
As result, for a short period after the Second World War, the Yugoslav and Bulgarian Communist leaders Josip Broz Tito and Georgi Dimitrov worked on a project to merge their two countries into a Balkan Federative Republic. As a concession to the Yugoslavian side, Bulgarian authorities agreed to the recognition of a distinct Macedonian ethnicity and language as part of their own population in the Bulgarian part of geographical Macedonia. This was one of the conditions of the Bled Agreement, signed between Yugoslavia and Bulgaria on 1 August 1947. In November 1947, pressured by both the Yugoslavs and the Soviets, Bulgaria also signed a treaty of friendship with Yugoslavia. The Bulgarian president Georgi Dimitrov was sympathetic to the Macedonian Question. The Bulgarian government Communist party was compelled once again to adapt its stand to Soviet interests in the Balkans. The policies resulting from the agreement were reversed after the Tito–Stalin split in June 1948, when Bulgaria, being subordinated to the interests of the Soviet Union, was forced to take a stance against Yugoslavia.
- Balkan federation: a history of the movement toward Balkan unity in modern times, Smith College studies in history, Leften Stavros Stavrianos, Archon Books, 1964, p. 149.
- Georgi Dimitrov. "The Significance of the Second Balkan Conference". Archived from the original on 4 September 2006. Retrieved August 2, 2006.
- v, Joseph. The Communist Party of Bulgaria; Origins and Development, 1883–1936. Columbia University Press. p. 126.
- A. Cook, Bernard (2001). Europe Since 1945: An Encyclopedia. Taylor & Francis. p. 810. ISBN 0-8153-4058-3.
- Coenen-Huther, Jacques (1996). Bulgaria at the Crossroads. Nova Publishers. p. 166. ISBN 1-56072-305-X.
- At the time the term "Slavomacedonian" was not considered offensive: the Greek Helsinki Monitor reports that the term, "was accepted by the community itself". However, today the term has pejorative connotations.
- Niel Simpson, Macedonia;Its Disputed History,Aristoc Press.1994
- Ramet, Pedro (1989). Religion and Nationalism in Soviet and East European Politics. Duke University Press. p. 374. ISBN 0-8223-0891-6.
- Neil, Simpson (1994). Macedonia; Its disputed history. Aristoc Press. p. 89. ISBN 0-646-20462-9.
- Stavrianos, L. (1964)
- E. Kofos (1964) Nationalism and Communism in Macedonia; Thessaloniki, Institute of Balkan Studies