At the turn of the 20th century, the Ottoman Empire was crumbling, and the lands they had held in Eastern Europe for over 500 years were passing to new rulers.
Macedonia and Thrace were regions of indefinite boundaries, adjacent to the recently independent Greek, Bulgarian and Serbian states, but themselves still under the control of the Ottoman Turks.
Each of the neighbouring states based claims to Macedonia and Thrace on various historical and ethnic composition grounds.
But the population was highly mixed, and the competing historical claims were based on various empires in the distant past.

The competition for control took place largely by means of propaganda campaigns, aimed at winning over the local population, and took place largely through the churches and schools.
Various groups of mercenaries were also supported, by the local population and by the three competing governments.

The most effective group was the Internal Macedonian-Adrianopolitan Revolutionary Organization (IMARO), founded in Thessaloniki in 1893.
The group had a number of name changes prior to and subsequent to the uprising.
It was predominantly Bulgarian and supported an idea for autonomy for Macedonia and Adrianople regions within the Ottoman state with a motto of "Macedonia for the Macedonians".
It rapidly began to be infiltrated by members of Macedonian Supreme Committee, a group formed in 1894 in Sofia, Bulgaria.
This group was called the Supremists, and advocated annexation of the region by Bulgaria.

Since the term autonomy was regularly used in relation to the Macedonian Question, it is essential to note its sense and reason.
Its inspiration certainly belonged to the nineteenth-century Balkan practice whereby the powers maintained the fiction of Ottoman control over effectively independent states under the guise of autonomous status within the Ottoman state; (Serbia, 1829–1878; Romania, 1829–1878; Bulgaria, 1878–1908).
Autonomy, in other words, was as good as independence.
Moreover, from the Macedonian perspective, the goal of independence by autonomy had another advantage.
More important, IMARO was aware that neither Serbia nor Greece could expect to obtain the whole of Macedonia and, unlike Bulgaria, they both looked forward to and urged partition.
Autonomy, then, was the best prophylactic against partition, that would preserve the Bulgarian character of Christian Macedonian Slav population despite the separation from Bulgaria proper.
The idea of Macedonian autonomy was strictly political and did not imply a secession from Bulgarian ethnicity.

The two groups had different strategies.
IMARO as originally conceived sought to prepare a carefully planned uprising in the future, but the Supremacists preferred immediate raids and guerilla operations to foster disorder and a precipitate interventions.
On the other hand, a smaller group of conservatives in Salonica organized a Bulgarian Secret Revolutionary Brotherhood (Balgarsko Tayno Revolyutsionno Bratstvo).
The latter was incorporated in IMARO by 1902 but its members as Ivan Garvanov, were to exert a significant influence on the organization.
They were to push for the Ilinden–Preobrazhenie Uprising and later became the core of IMRO right-wing faction.
One of the founding leaders of IMARO, Gotse Delchev, was a strong advocate for proceeding slowly, but the Supremacists pressed for a major uprising to take place in the summer of 1903.
Delchev himself was killed by the Turks in May 1903.

Meanwhile, in late April 1903, a group of young anarchists from  the Gemidzhii Circle - graduates from the Bulgarian Men's High School of Thessaloniki launched a campaign of terror bombing, the so-called Thessaloniki bombings of 1903.
Their aim was to attract the attention of the Great Powers to Ottoman oppression in Macedonia and Eastern Thrace.
As a response to the attacks, the Turkish Army and bashibozouks (irregulars) massacred many innocent Bulgarians in Thessaloniki, and later in Bitola.

By these circumstances the Supremacists' plan went ahead.
Under a leadership from Ivan Garvanov IMARO made a decision ab
At the turn of the 20th century, the Ottoman Empire was crumbling, and the lands they had held in Eastern Europe for over 500 years were passing to new rulers. Macedonia and Thrace were regions of indefinite boundaries, adjacent to the recently independent Greek, Bulgarian and Serbian states, but themselves still under the control of the Ottoman Turks. Each of the neighbouring states based claims to Macedonia and Thrace on various historical and ethnic composition grounds. But the population was highly mixed, and the competing historical claims were based on various empires in the distant past.
The competition for control took place largely by means of propaganda campaigns, aimed at winning over the local population, and took place largely through the churches and schools. Various groups of mercenaries were also supported, by the local population and by the three competing governments.
The most effective group was the Internal Macedonian-Adrianopolitan Revolutionary Organization (IMARO), founded in Thessaloniki in 1893. The group had a number of name changes prior to and subsequent to the uprising. It was predominantly Bulgarian and supported an idea for autonomy for Macedonia and Adrianople regions within the Ottoman state with a motto of "Macedonia for the Macedonians". It rapidly began to be infiltrated by members of Macedonian Supreme Committee, a group formed in 1894 in Sofia, Bulgaria. This group was called the Supremists, and advocated annexation of the region by Bulgaria.
Since the term autonomy was regularly used in relation to the Macedonian Question, it is essential to note its sense and reason. Its inspiration certainly belonged to the nineteenth-century Balkan practice whereby the powers maintained the fiction of Ottoman control over effectively independent states under the guise of autonomous status within the Ottoman state; (Serbia, 1829–1878; Romania, 1829–1878; Bulgaria, 1878–1908). Autonomy, in other words, was as good as independence. Moreover, from the Macedonian perspective, the goal of independence by autonomy had another advantage. More important, IMARO was aware that neither Serbia nor Greece could expect to obtain the whole of Macedonia and, unlike Bulgaria, they both looked forward to and urged partition. Autonomy, then, was the best prophylactic against partition, that would preserve the Bulgarian character of Christian Macedonian Slav population despite the separation from Bulgaria proper. The idea of Macedonian autonomy was strictly political and did not imply a secession from Bulgarian ethnicity.
The two groups had different strategies. IMARO as originally conceived sought to prepare a carefully planned uprising in the future, but the Supremacists preferred immediate raids and guerilla operations to foster disorder and a precipitate interventions. On the other hand, a smaller group of conservatives in Salonica organized a Bulgarian Secret Revolutionary Brotherhood (Balgarsko Tayno Revolyutsionno Bratstvo). The latter was incorporated in IMARO by 1902 but its members as Ivan Garvanov, were to exert a significant influence on the organization. They were to push for the Ilinden–Preobrazhenie Uprising and later became the core of IMRO right-wing faction. One of the founding leaders of IMARO, Gotse Delchev, was a strong advocate for proceeding slowly, but the Supremacists pressed for a major uprising to take place in the summer of 1903. Delchev himself was killed by the Turks in May 1903.
Meanwhile, in late April 1903, a group of young anarchists from  the Gemidzhii Circle - graduates from the Bulgarian Men's High School of Thessaloniki launched a campaign of terror bombing, the so-called Thessaloniki bombings of 1903. Their aim was to attract the attention of the Great Powers to Ottoman oppression in Macedonia and Eastern Thrace. As a response to the attacks, the Turkish Army and bashibozouks (irregulars) massacred many innocent Bulgarians in Thessaloniki, and later in Bitola.
By these circumstances the Supremacists' plan went ahead. Under a leadership from Ivan Garvanov IMARO made a decision ab
Ilinden–Preobrazhenie Uprising