Early examples of mass dislocations include the expulsion of the Jews and the Moors from Spain in the 15th cent., the flights from religious persecutions in Europe to the New World in the 16th and 17th cent., and the exodus of the émigrés in the French Revolution. Before the 20th cent. there was little or no systematic attempt to help refugees, although some groups, on a private basis, provided assistance to refugees who were coreligionists.
After World War I, international organizations were created to give assistance. 1.5 million Russians fled the Revolution of 1917; in the 1920s large numbers of Armenian and Greek refugees fled from Turkey, and many Bulgarians left their country. In 1921 the League of Nations appointed Fridtjof Nansen its high commissioner for refugee work; later the International Labor Organization and the Nansen International Office for Refugees took charge. Nansen effected repatriation wherever possible; in other cases he arranged for the issuance of Nansen passports, recognized by 28 countries, which gave the holder the right to move freely across national boundaries.
The refugee problem was revived after Hitler's accession to power in Germany (1933) and his annexation of Austria (1938) and Czechoslovakia (1939) and the persecution of Jews. The Loyalist defeat in Spain (1939) and anti-Semitic legislation in Eastern Europe added to the overall problem. Many asylum governments attempted to return refugees to their country of origin; they were often forbidden to work and sometimes imprisoned. Some progress was achieved with the establishment of a permanent committee for refugees in London after a conference of 32 nations held in France in 1938.
World War II further dislocated civil populations. At the war's end the United Nations Relief and Rehabilitation Administration (UNRRA) had the responsibility of caring for some 8 million displaced persons (persons removed from their native countries as prisoners or slave laborers). Most were eventually repatriated, but about one million in Germany, Austria, and Italy refused to return to their native countries, which were by then under Communist governments. The number of Jewish refugees was in time greatly reduced by emigration to Israel, but uprooting the Arab population of that new state in turn created some one million refugees. With the end of UNRRA, the United Nations created the International Refugee Organization to carry on its work. After much debate the United States in 1948 adopted the Displaced Persons Act, which, despite numerous restrictions, eventually permitted the entrance of about 400,000 immigrants.