The study examined the rationale behind the conflict between two major ethnic group who shared considerable cultural similarities which would have engendered nation-building but turned out to create around for massive killings termed Rwanda Genocide. It also interrogated the narrow UNAMIR mandate which was limited to monitoring, assisting and investigating crime and violence arising from the Arusha Accord. Descriptive study method was utilized which focused on the character and actions of the personages that were involved in all actions which led to sustain and failed in halting the genocide. The ‘just-war theory was the framework for evaluating the ineptitude of the UNO in halting the Genocide. The practice of Anthroprometry deepened segregation between the ethnic groups. The failure of nation-building escalated by the French colonialist exacerbated. The UNO failed to act as at when due perhaps because Rwanda was not considered of strategic importance to the holder of veto powers at the UNO. It then posited the need for Peace-Enforcement rather than Peacekeeping in every situation where the UN facilitates an Accord. This is because when two or more groups are in conflict or at war, it means peace is absent. It would be a grand deception to pursue ‘peace-keeping’ where nonexisted. Every UNO mission must have its communication radio and interpreters to avoid language problem which complicated the problem in Rwanda. There should be a sociological understanding of the problem they have gone resolve in order to be strategic in their operations by knowing hardliners who are ready to sabotage the mission.