Twenty years ago, the Doctors Without Borders/Médecins Sans Frontières (MSF) team in Kigali saw the town descend into violence. These were the first days of what would go on to become known as genocide. Throughout their stay, the organization's humanitarian principles were often violated by the perpetrators of the genocide. This lead to the startling realization of the limits of humanitarian action. For the first and only time in its history, MSF made a public demand for armed intervention, pointing out a very simple truth: doctors can't stop genocide.