Assassination of Juvénal Habyarimana and Cyprien Ntaryamira form a coalition government, ratification of the Arusha Accords was impossible. The most extreme of the Hutu parties, the CDR, which openly called for ethnic cleansing of the Tutsi, was entirely unrepresented in the Accords. The security situation deteriorated throughout 1993. Armed Hutu militias attacked Tutsis throughout the country, while high-ranking adherents of Hutu Power began to consider how the security forces might be turned to genocide. In February 1994, Roméo Dallaire, the head of the military force attached to the United Nations Assistance Mission for Rwanda (UNAMIR), which had been sent to observe the implementation of the Arusha Accords,
Hutu of Rwandan national unity, but has been criticized as an attempt at historical revisionism. Still others suggest that the two groups are related but not identical, and that differences between them were exacerbated by Europeans, or by a gradual, natural split, as those who owned cattle became known as Tutsi and those who did not became Hutu. Mahmood Mamdani states that the Belgian colonial power designated people as Tutsi or Hutu on the basis of cattle ownership, physical measurements and church records. There is an ongoing debate as to whether the Hutu and Tutsi are really separate groups or not;