Thirty-plus years of warfare in Vietnam forced various groups to shift locations both within Southeast Asia and beyond. The most substantial exodus of people, however, came between the late 1970s and mid-1980s, after the government of South Vietnam collapsed and Saigon came under communist control in April 1975. Subsequently, increasing numbers of political refugees from Vietnam, Laos, and Cambodia entered the United States and other countries.

During their last years in South Vietnam, political officials, educators, lawyers, doctors, and others connected to the former Saigon government feared for their lives and those of their families. Many left the country, often secretively and under dangerous conditions. The Vietnamese government reportedly developed reeducation camps in isolated areas, both to punish and to indoctrinate an estimated 50,000 to 400,000 people, an estimated 250,000 of whom died.

An estimated 700,000 to 2.5 million people attempted to leave Vietnam by sea after...