In the early years of the organisation, membership eligibility was exclusive to Bulgarians, but later it was extended to all inhabitants of European Turkey regardless of ethnicity or religion. The majority of its members were Macedonian Bulgarians. In 1903, IMRO organised the Ilinden–Preobrazhenie Uprising against the Ottomans, which after some initial successes, including the forming of the Kruševo Republic, was crushed with much loss of life. The uprising and the forming of the Kruševo Republic are considered the cornerstone and precursors to the eventual establishment of the Macedonian state. The leaders of the Ilinden uprising are celebrated as national heroes in North Macedonia. The names of IMRO revolutionaries like Gotse Delchev, Pitu Guli, Dame Gruev and Yane Sandanski were included into the lyrics of the national anthem of the state of North Macedonia "Denes nad Makedonija" ("Today over Macedonia"). The major national holiday of North Macedonia, the Republic Day, is celebrated on 2 August, Ilinden (St. Elijah day), the day of the Ilinden uprising.