In 1994 Rwandan genocide approximately 1 million people were killed in three months. This genocide took place in the presence of the United Nations forces deployed there. In spite of the signals of the coming genocide, international community could not do much to prevent or stop this genocide. Therefore it was a “failure”. This study aims to identify the principal political and strategic constraints explaining the failure of the UN and international community as a whole to address the genocide in Rwanda. It examines the events that led to UN intervention and describes UN action. It also aims at determining the position of Rwanda case in the evolution of the doctrine and practice of humanitarian intervention. This study asks questions like “How can we define the UN intervention in Rwanda?”, “How does the Rwanda case reveal the difficulties the UN face with, in terms of humanitarian intervention?”, “What are the reasons for this failure?” and “What lessons should be taken from the experience?”. It concludes that in the absence of a general doctrine guiding humanitarian intervention, and a solid mechanism capable of taking action when necessary, the decision on whether or not to intervene will be caught up in politics. Rwanda experience suggests that intervention is most likely where perceived national and ethical interests converge, less so when they conflict.