Three tribes coexist in Rwanda. The Hutus are the majority (85%), with a small Tutsi minority (14%) and an even smaller number of Twa (1%), who are pygmies mainly living in the forest.
Before the German and Belgian colonial eras, the Tutsis were usually socially superior to the Hutus, but the tribes still intermarried and social mobility was frequent. From 1894 to 1918, Rwanda was a part of German East Africa’s colonial rule, and then, along with Burundi, fell under Belgium’s mandate after World War I.
During this colonial period the Belgians favored the Tutsis, who had already been in power, but their colonialist structure exacerbated the class dynamics between the two groups and led to significant amounts of ethnic tension. Ethnic violence continued to build up until the genocide.
In 1959, the Hutus revolted against the Tutsi monarchy, which forced 300,000 Tutsis out of the country, and then the country gained independence from the Belgians in 1962. With the Hutus in power, Tutsis continued to be oppressed for decades. Tutsi refugees in Tanzania and the Congo (then Zaire) would periodically try to reclaim Rwandan power; this fueled further Hutu attacks and expulsions of Tutsis still in Rwanda.
The Rwandan Patriotic Front, or RPF, was a group composed of Tutsi refugees who wanted to return to their positions in Rwanda. In 1990 they invaded Rwanda from their base in Uganda. After the long-standing Rwandan president Habyarimana signed a peace agreement with the RPF, including them in a new transitional government, Hutu extremists grew angry.
The genocide was catalyzed when the president’s plane was shot down and he died. No one knows who did it: it could have been Hutu extremists or the RPF. This incident incensed the Hutu extremists militia, the Interhamwe, to begin the genocide on April 7th 1994.
Over the next 100 days in Rwanda, 800,000 Tutsi and moderate Hutus were killed in a genocide. The RPF was simultaneously fighting the Rwandan army in a civil war, and when they took Kigali, the war and genocide ended. A new coalition government was subsequently elected. Since 2003, a new constitution has been in place, in which ethnicity is not mentioned.