Towards the end of the 19th century, Macedonia was still part of the Ottoman Empire. Considered as the ‘jewel in the Ottoman crown’, the Turks would not give Macedonia up without a fight. A failed uprising in 1878 meant that the Macedonians needed to be more organized and better prepared if they were to free themselves from their oppressors.
In 1893, six men met in Solun to discuss the inception and creation of a Macedonian body that would fight for freedom and liberty. This organization was founded by Hristo Tatarchev, Dame Gruev, Petar Pop-Arsov, Andon Dimitrov, Hristo Batandzhiev and Ivan Hadzhinikolov, and was initially given the name of MRO (Macedonian Revolutionary Organization).
The organization grew rapidly and by the 2nd of August, 1903, MRO boasted some 20,000 members, each as loyal to the Macedonian cause as the next. Loyalty was given by blood oath and swearing fealty and allegiance to the organization. Usually performed by a priest, a new member would kneel before a revolver and a dagger that rested on a bible and would recite the following words:
"I swear by God, my faith and honor, that I will fight to the death for the freedom of the Macedonians in Macedonia, that I will submit unconditionally to the leadership and will unprotestingly carry out its orders; that I will betray no one neither by word nor deed the secret to which I wed myself today, and all that I shall see, hear and understand concerning the cause from today on. If I break my oath, let me be killed by one of the comrades, with the revolver or the dagger which here I kiss."
The person taking the oath would bow three times, kiss the objects, which, after the oath has been pronounced, he would kiss once again. This oath first appeared in the public eye via the British consular records in 1902.
The organization itself was highly organized and careful during its existence. A series of underground communication networks consisted of men and women traveling in secret to deliver hand written messages, and was considered the spine of the organization and paramount to its survival.
In 1903, having gained substantial support among the Macedonians, MRO staged the Ilinden Uprising, a significant but unsuccessful rebellion that was rapidly suppressed by the Ottoman authorities. Following the Ilinden Uprising, the idea of Macedonian statehood was revealed in the conviction that "the masses (the Macedonian people) should not rely on the possibility that Bulgaria or any other country might come and liberate them". At the same time, the future of Macedonia was defined as that of a state with independent status within a Balkan federation.
Agreed on at the General Congress held in the Rila Monastery in 1905, the ideological, political and statutory grounds for the establishment of a new, de facto, Macedonian state was born.
Subsequently, MRO split into two separate factions: a leftist, pro-Macedonian wing based in Macedonia, which continued to advocate for an independent Macedonia, and a rightist, pro-Bulgarian wing based in Sofia, which sought to annex Macedonia to Bulgaria and promoted Bulgarian political and military interests.
The leftist, pro-Macedonian wing of IMRO, which came together in 1925 as IMRO (United), continued to promote the cause of Macedonian nationalism and the establishment of an independent Macedonian state. While it gained some early support from the Balkan communist parties, it was later persecuted by the Yugoslav authorities on the grounds that its supporters were Macedonian separatists, and therefore posed a threat to the unity of the Yugoslav state. By 1937 IMRO (United) was disbanded.