The organization was founded in 1893 in Ottoman Thessaloniki by a small band of anti-Ottoman Macedono-Bulgarian revolutionaries, who considered Macedonia an indivisible territory and claimed all of its inhabitants ""Macedonians"", no matter their religion or ethnicity. In practice, IMRO was established by Bulgarians and most of their followers were Bulgarians. The organization was a secret revolutionary society operating in the late 19th and early 20th centuries with the goal of autonomous Macedonia and Adrianople regions. Initially, they were against the aspirations of neighboring states in the area and saw the future autonomous Macedonia and Southern Thrace as a multi-ethnic entity. It appears likely that at the early stages of the struggle, a desired outcome of the autonomy was unification with Bulgaria. This aim was changed later with the idea of transforming the Balkans into a federal state, in which Macedonia and Thrace would enter as equal members. The idea of autonomy was strictly political and did not imply a secession from Bulgarian ethnicity. Even those, who advocated for independent Macedonia and Thrace, never doubted the predominantly Bulgarian character of the Slavic population in both areas. The organization was founded by Hristo Tatarchev, Dame Gruev, Petar Pop-Arsov, Andon Dimitrov, Hristo Batandzhiev and Ivan Hadzhinikolov. Most of them (with the exception of Ivan Hadzhinikolov) were closely connected with the Bulgarian Men's High School of Thessaloniki. According to Hristo Tatarchev's "Memoirs", IMRO was first called simply the Macedonian Revolutionary Organization (MRO). Ivan Hadzhinikolov in his memoirs lists the five basic principles of the MRO's foundation: