The extravagant parties of the Ottoman ruling classes during the Tulip Period caused a lot of unrest among the Ottoman population. In September 1730, janissaries headed by Patrona Halil backed in Istanbul a rebellion by 12,000 Albanian troops which caused the abdication of Sultan Ahmed III and the death of the Grand Vizier Damad Ibrahim. The rebellion was crashed in three weeks with the massacre of 7,000 rebels, but it marked the end of the Tulip Era and the beginning of Sultan Mahmud I's reign. In 1804, the Dahias, the Janissary junta that ruled Serbia at the time, having taken power in the "Sanjak of Smederevo" in defiance of the Sultan, feared that the Sultan would make use of the Serbs to oust them. To forestall this they decided to execute all prominent nobles throughout Central Serbia, a move known as the Slaughter of the Knezes. According to historical sources of the city of Valjevo, the heads of the murdered men were put on public display in the central square to serve as an example to those who might plot against the rule of the Janissaries. The event triggered the start of the Serbian Revolution with the First Serbian Uprising aimed at putting an end to the 370 years of Ottoman occupation of modern Serbia.