Internal Macedonian Revolutionary Organization

The Internal Macedonian Revolutionary Organization (IMRO; Bulgarian: Вътрешна македонска революционна организация (ВМРО), romanized: Vatreshna Makedonska Revolyutsionna Organizatsiya (VMRO); Macedonian: Внатрешна македонска револуционерна организација (ВМРО), romanized: Vnatrešna Makedonska Revolucionerna Organizacija (VMRO)), was a secret revolutionary society founded in the Ottoman territories in Europe, that operated in the late 19th and early 20th centuries.

Founded in 1893 in Salonica, it initially aimed to gain autonomy for Macedonia and Adrianople regions in the Ottoman Empire, however, it later became an agent serving Bulgarian interests in Balkan politics. IMRO modeled itself after the earlier Bulgarian Internal Revolutionary Organization of Vasil Levski and accepted its motto "Freedom or Death" (Свобода или смърть). According to the memoirs of some founding and ordinary members, in the Organization's earliest statute from 1894, the membership was reserved exclusively for Bulgarians. It used the Bulgarian language in all its documents and in its correspondence. The Organisation founded its Foreign Representation in Sofia, Bulgaria in 1896. Starting in the same year, it fought the Ottomans using guerrilla tactics, and in this, they were successful, even establishing a state within a state in some regions, including their tax collectors. This effort escalated in 1903 into the Ilinden–Preobrazhenie Uprising. The fighting involved about 15,000 IMRO irregulars and 40,000 Ottoman soldiers. After the uprising failed, and the Ottomans destroyed some 100 villages, the IMRO resorted to more systematic forms of terrorism targeting civilians. Also, the Ilinden disaster splintered IMRO and signalled the beginning of a fratricidal conflict between the left-wing faction ("federalists") who continued to favor autonomy as step towards independent Macedonia inside a Balkan Federation, and the right-wing faction ("centralists") which favored unification with Bulgaria. The division was based partially on ideology, and partly in terms of personality and locality, and it would plague the Macedonian revolutionary movement over the next decades.

During the Balkan Wars and the First World War, the organization supported the Bulgarian army and joined Bulgarian war-time authorities when they temporarily took control over parts of Thrace and Macedonia. As for the Balkan Wars the division of the area among the Balkan states, was seen by the IMRO's adherents as entailing the partition of Macedonia. Retaining the unity of Macedonia seemed crucial in this period for IMRO, autonomism as a political tactic was abandoned, and annexationist positions were supported, aiming eventual incorporation of occupied areas into Bulgaria. The desire to size most of Macedonia and Thrace within a Bulgarian state lay behind the Bulgarian decision to enter each of these three wars. The Bulgarian government first attached the IMRO chetas as auxiliaries of its army in the Balkan wars and then drafted the former paramilitaries directly into it, as Bulgarian military personnel during the First World War. IMRO arose then from a clandestine organization into an important factor of the Greater Bulgarian policy, supporting the Bulgarisation of the area. Additionally, some guerrilla companies formed by IMRO-irregulars, participated in several massacres of Serbs in the areas of Azot, Skopska Crna Gora and Poreče. Regular Bulgarian troops took control of the region while komitadjis were appointed mayors or prefects and served as gendarmerie corps. IMRO detachments participated in the suppression of the Serbian Toplica uprising.

After the First World War the combined Macedonian-Thracian revolutionary movement separated into two detached organizations, IMRO and ITRO. Simultaneously, the "federalists" split up and formed the Macedonian Federative Organization and later IMRO (United). After this the IMRO earned a reputation as an ultimate terror network, seeking to change state frontiers in the Macedonian regions of Greece and Serbia (later Yugoslavia). They contested the partitioning of Macedonia and launched raids from their Petrich stronghold into Greek and Yugoslav territory. Their base of operation in Bulgaria was jeopardized by the Treaty of Niš, and the IMRO reacted by assassinating Bulgarian prime minister Aleksandar Stamboliyski in 1923, with the cooperation of other Bulgarian elements opposed to him. In 1925 the Greek army launched a cross-border operation to reduce the IMRO base area, but it was ultimately stopped by the League of Nations, and IMRO attacks resumed. A conflict over the leadership arose and Ivan Mihailov ordered the assassination of Aleksandar Protogerov, which sparked a fratricidal war between the so called "Mihailovists" and "Protogerovists". In the interwar period the IMRO also cooperated with the Croatian Ustaše, and their ultimate victim was Alexander I of Yugoslavia, assassinated in France in 1934. After the Bulgarian coup d'état of 1934, their Petrich stronghold was subjected to a military crackdown by the Bulgarian army, and the IMRO was reduced to a marginal phenomenon.

The organization changed its name on several occasions, but the name VMRO (IMRO) remained most noted. After the fall of communism in the region, numerous parties claimed the IMRO name and lineage to legitimize themselves. Among them, the right-wing parties established in the 1990s, "VMRO-BND" in Bulgaria and "VMRO-DPMNE" in then Republic of Macedonia.