Hutu Rwanda, this led to the "Social revolution" and Hutu violence against Tutsis. Tens of thousands of Tutsis were killed and many others fled to neighboring countries, such as Burundi, Uganda and expanding the Banyamulenge Tutsi ethnic group in the South Kivu region of the Belgian Congo. Later, exiled Tutsis from Burundi invaded Rwanda, prompting Rwanda to close its border with Burundi. In Burundi, a campaign of genocide was conducted against Hutu population in 1972, and an estimated 100,000 Hutus died. In 1993, Burundi's first democratically elected president, Melchior Ndadaye, who was Hutu, was believed to be assassinated by Tutsi officers,
Tutsi after mid-1600. Beginning in about 1880, Roman Catholic missionaries arrived in the Great Lakes region. Later, when German forces occupied the area during World War I, the conflict and efforts for Catholic conversion became more pronounced. As the Tutsi resisted conversion, missionaries found success only among the Hutu. In an effort to reward conversion, the colonial government confiscated traditionally Tutsi land and reassigned it to Hutu tribes. In Burundi, meanwhile, Tutsi domination was even more entrenched. A ruling faction, the Ganwa, soon emerged from amongst the Tutsi and assumed effective control of the country's administration. The area was ruled as