After the catastrophic failure of the UN and western nations to prevent and halt genocide in Rwanda in 1990, many pledged “never again.” In less than ten years, the ethnic cleansing in Kosovo provided the international community with a chance at redemption. Without waiting for UN approval, NATO forces led a military intervention to stop Milošević’s campaign of violence against the Kosovo Albanians. The bombing of Kosovo is now considered to be the first ever intervention in another sovereign nation by the international community for humanitarian purposes. However, the lack of legal backing from UN rendered the intervention suspect, putting into question the moral justification of the bombing campaign which led to the death of many civilians. As such, the humanitarian intervention in Kosovo left many questions for the international community: Who should intervene to stop genocide or ethnic cleansing taking place in a given state? When should the international community intervene? What renders a humanitarian intervention legal from the perspective of international law? In the early 2000s, there was a shared sense in the international community that there was an urgent need to set an international framework for humanitarian intervention. The Responsibility to Protect (R2P) doctrine aimed to provide that framework. Approaching the topic from the perspective of constructivist theory, the thesis describes how the R2P emerged as a potential international norm, cascaded through the international community, and then became diffused enough to be utilized by the UN to address the mass atrocities that took place in Darfur. The 2011 intervention in Libya became the test case for the R2P. Utilizing the R2P doctrine the Security Council approved a resolution that authorized use of force by the international community to stop mass atrocities in Libya by any means necessary. However, the moment of the R2P’s success was also its downfall. Many argued that NATO powers used R2P as an ideological tool to protect their national interests in Libya, instead of truly seeking to prevent genocide and other crimes against humanity for moral reasons. Despite the diffusion of R2P as a well accept norm and its use in the Security Council in 2011, the failure of intervention in Libya has led to the regression of the norm. I argue that this regression has caused the lack of humanitarian intervention in the ethnic cleansing and violence in Myanmar against the Rohingya population.