As before and during the Holocaust, people flee when their lives and communities are at risk. The massive movement of populations can therefore be a warning sign of genocide or the threat of genocide. In Sudan's western region of Darfur, for which the United States Holocaust Memorial Museum declared a Genocide Emergency in July 2004, hundreds of thousands of Darfurians fled across the border into Chad. Some two million more were displaced inside Darfur, while up to 400,000 perished from violence and the conditions of life inflicted on targeted groups.

The recognition of a moral failure in responding to Jews and others fleeing persecution before World War II, and the need to deal with the many people left displaced at war's end, led to important international developments. In 1948, the Universal Declaration of Human Rights proclaimed that everyone has the right to seek and enjoy asylum from persecution. In 1950, the office of the United Nations High Commissioner for Refugees (UNHCR) was created. And in 1951, the United Nations Convention on Refugees laid the foundation for the basic international obligation not to return people to countries where their life or freedom would be threatened, an obligation the United States accepted in 1968.