Rwanda, in The Oxford International Encyclopedia of Peace (Nigel J. Young ed., 2010)

Tensions between the Hutu and Tutsi ethnic groups have existed throughout Rwandan history. On numerous occasions these tensions induced violence, although the amplitude of the 1994 violence was unprecedented. Ethnic tensions were exacerbated by colonial interventions, in particular those effected by the Belgians. The Belgian colonial administrators took a liking to the Tutsi people. They treated them preferentially, angering the majority Hutu people. In 1933, the Belgian colonial administration passed a law requiring every Rwandan to carry an ethnic identity card. The lines between Tutsi and Hutu groups, which traditionally had been porous and informal, suddenly became permanent and legalized. The ethnic identity card requirement persisted after Rwandan independence in 1960. Tragically, the continued presence of this requirement accelerated the genocide, insofar as persons unable to produce a Hutu card simply were slaughtered. Accordingly, genocide in Rwanda can, to some degree, be traced to colonial policies that exacerbated ethnic conflict.