soldiers and police in Rwanda. The duration of the 1994 genocide is usually described as 100 days, beginning on April 6 and ending in mid-July. The tension between the majority Hutu and the minority Tutsi had developed over time but was particularly emphasized late in the nineteenth century and early in the twentieth century as a result of German and Belgian colonialism over Rwanda. The ethnic categorization of the two was an imposed and an arbitrary construct based more on physical characteristics than ethnic background. However, the social differences between the Hutu and the Tusi have traditionally allowed the Tutsi, with a strong pastoralist tradition, to gain social, economic, and political ascendancy over the Hutu, who were primarily agriculturalists. The distinction under colonial powers allowed Tutsis to establish ruling power until a Hutu revolution in 1959 abolished the Tutsi monarchy by 1961. The hostility between the two groups continued, as "additional rounds of ethnic tension and violence flared periodically and led to mass killings of Tutsi in Rwanda, such as in 1963, 1967, and 1973". The establishment of the Rwandan Patriotic Front (RPF) and its invasion from Uganda furthered ethnic hatred. A ceasefire in these hostilities led to negotiations between the government and the RPF in 1992. On April 6, 1994, a plane carrying then-President Juvenal Habyarimana, and Cyprien Ntaryamira of Burundi was shot down, killing everyone on board. The Hutu held the RPF accountable and immediately began the genocide, targeted at both Tutsis and Hutu moderates. Most of the killing during the Rwandan genocide was carried out by the radical Hutu groups known as the Interahamwe and the Impuzamugambi. Radio broadcasts also were an integral part of the genocide, which further fueled the genocide by encouraging Hutu civilians to kill their Tutsi neighbours, labeled as "cockroaches" in need of extermination. Despite its colossal scale, particularly within such a short period of time, the genocide was carried out almost entirely by hand, usually with the utilization of machetes and clubs. Various atrocities committed include the rape of thousands of Tutsi women, as well as the dismemberment and disfigurement of victims. Frequently the killers were people the victims knew personally—neighbors, workmates, former friends, sometimes even relatives through marriage. At least 500,000 Tutsis were killed, and approximately 2 million refugees (mostly Hutus) left for refugee camps of neighboring Burundi, Tanzania, Uganda, and former Zaire. Establishment of the ICTR The United Nations Assistance