Refugees are persons who have fled their country or been expelled from it and cannot or will not return, because of natural catastrophe, war or military occupation, or fear of religious, racial, or political persecution. Although refugees have existed throughout human history, the problem has assumed more importance in the 20th century. It is estimated that more than one hundred million persons have left their home country, since the outbreak of World War II. According to the United Nations High Commissioner for refugees, the outstanding world refugee total exceeded twenty-six million in 1996. Deprived of the protection of their state, often detached from their families and communities